VEGETATIVE PROPAGATION OF THE BLACK WALNUT

With S p e c ia l R eference to the F actors
I n flu e n c in g C a llu s Formation and
Union in G ra ftin g .

T h esis

Subm itted to th e F a c u lty o f the M ichigan S ta te
C o lleg e o f A g r ic u ltu r e and A pplied S cien ce
in P a r tia l F u lfillm e n t o f th e Re­
quirem ents fo r the Degree o f
D octor o f P h ilosop h y.

by
Benjamin G a illa rd S i t t on
June, 1931.

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VEGETATIVE PROPAGATION OF THE BLACK WALNUT

With S p e c ia l R eference t o th e F a cto rs
In flu e n c in g C a llu s Formation and
Union in G ra ftin g . ^

B.

G. S it t o n , A sso c ia te P om ologist,
Nut C ulture I n v e s t ig a tio n s ,
U nited S ta te s Department o f A g r ic u ltu r e .

INTRODUCTION.
V e g e ta tiv e p ropagation o f th e b lack walnut
( JugLans n ig ra ) i s u s u a lly attend ed w ith u n c e r ta in ty and
d iffic u lty .

In some c a s e s very s a t is f a c t o r y r e s u lt s have

been secu red , w h ile , a t other tim e s, although, th e same
o p erator a p p aren tly used th e same methods and c a r e , r e ­
s u l t s showed very u n s a tis fa c to r y p ercen tage o f s u c c e s s fu l
g r a fts.

1 . Subm itted to the F a cu lty o f the M ichigan S ta te C ollege
o f A g ric u ltu r e and A pplied S cien ce as a t h e s i s in p a r t ia l
f u lf illm e n t o f the requirem ents fo r th e degree o f Doctor o f
P h ilo so p h y . Work rep orted h erein was begun in 1926 vd iile the
author was in re sid e n c e a t Michigan S ta te C o lle g e , and was
continued th ere u n t i l 1929. The o f f i c i a l s o f th e U nited
S t a te s Department o f A g r ic u ltu r e k in d ly p erm itted the c o n tin ­
u a tio n o f th e work during 1930 and 1931.

1

I t i s d e s ir a b le to know why th e walnut i s so d i f f i ­
c u lt to propagate v e g e t a t iv e ly and t o fin d some means o f
in c r e a s in g th e degree o f s u c c e ss , i f p o ssib le *

With th e se

c o n s id e r a tio n s in mind, the work rep orted h e r e in was
undertaken*

REVIEW OF LITERATURE.
Much o f th e l it e r a t u r e on asexu al propagation o f
th e Juglandaceae i s concerned w ith the probably unimportant
d e t a i l s o f v a r io u s methods which d if f e r v e r y s l i g h t l y , or
n ot a t a l l , in th e e s s e n t ia l p o in ts*

Most o f i t r e l a t e s to

v e g e t a tiv e p rop agation o f Juglans r e g ia , the s o - c a lle d
E n g lish walnut*

One group o f w r ite r s fa v o rs th e c l e f t g r a ft

to th e e x c lu sio n o f a l l oth er m ethods, w h ile o th e r s th in k
v a r io u s ly th a t th e f l u t e g r a f t , th e g o a tf s fo o t g r a f t , or th e
sadd le g r a f t , i s th e o n ly one th a t should be fo llo w e d .
Among th e a r t i c l e s which favor th e f l u t e g r a ft i s the
e a r l i e s t account regard in g asexu al propagation o f th e P e r sia n ,
or E n g lish walnut ( Ju glans r e g ia ) ,
a t t e n t io n .

which has come to the w r ite r 1 s

T h is i s found in Theatre d1A g ricu ltu re by O liv er de

2

S e r r e s (5 1 ) , as printed, in 1805.

Leroy (2L) comments on th e method

d e sc r ib e d , a p p aren tly having th e f i r s t e d it io n a v a ila b le .
De S e r r e s s t a te s th a t th e walnut i s propagated by the
"Canon g r e ffe " upon th e new sh o o ts o f th e p reced in g year in the
sp r in g or summer.

T h is method i s v a r io u s ly c a lle d canon ( c y lin d e r ) ,

cornachet (sm a ll h o rn ), tu ia n ( tu b u la r ), s i f f l e t (w h is tle ) and
f lu s t e a n ( f l u t e ) .

The c io n and sto ck are matched as to diam eter so

th a t th e cion may f i t t i g h t l y on th e sto ck .

The sh o o ts fo r th e cy­

lin d e r (bud) are chosen and gathered at the ends o f th e p r in c ip a l
la r g e and v ig o ro u s branches, a void in g slen d er sh o o ts.
and th e d i s t a l p o r tio n o f the stem are cut away.

The le a v e s

A p o r tio n o f the

c io n two or th r e e f in g e r s lo n g i s r o ta te d between the f in g e r s g en t­
l y to sep a ra te th e bark from th e wood, cu t and s ta r te d from the
wood by a s li g h t t w i s t .

On th e s to c k , a branch equal in s iz e to

th e cio n i s c u t, the bark s p l i t len g th w ise in th r e e or fou r p la c e s
and sep arated from th e wood f o r a le n g th equal t o , or s l i g h t l y
lo n g e r , than th e c y lin d e r .
th e s to c k .

The c y lin d e r i s removed and slip p e d on

The c y lin d e r must j o in th e wood p e r f e c t ly .
In d is c u s s in g t h i s method o f p ropagation, P o itea u (44)

says t h a t, though i t i s d e s ir a b le to have th e sto ck and the cio n a s
n e a r ly a s p o s s ib le th e same diam eter, t h is i s not n e c e ssa r y .

Tlien

th e f la g e o le t (c y lin d e r ) i s too t i g h t , i t may be s p l i t lo n g itu d in a l­
l y on th e s id e away from th e bud, and a s tr ip o f bark o f the sto ck
used to f i l l the gap.

I f th e circum ference o f the c y lin d e r i s too

g r e a t, f i t t i n g i s a tta in e d by removal o f a lo n g itu d in a l s t r i p .

A ll

3

p a r ts of* th e c y lin d e r should be p ressed c lo s e t o th e wood o f th e
sto ck ; u s u a lly a lig a t u r e i s n e c e ssa r y to accom plish t h i s ,
Gagnaire ( 2 4 ), M o r t ille t ( 3 9 ), and o th e r s ( 3 ) , say th a t
th e f l u t e g r a ft i s the o n ly method p r a c tic a b le f o r u se in th e nur­
sery*

M artin (34) says t h i s method i s conmonly used in southern

France*

M o r t ille t (39) r e p o r ts th a t th e most exp erien ced workers

succeed w ith o n ly o n e -th ir d o f th e f l u t e g r a f ts set*

The o p era tio n

demands s k i l l and care to remove th e c y lin d e r w ithout in ju r y t o it *
He s t a t e s th a t the o p era tio n should be delayed u n t i l danger o f
sp rin g f r o s t s i s past*
In France about 1830, and in f a c t much l a t e r , i t was
th e p r a c tic e to g r a ft walnut t r e e s o n ly a f t e r th ey began to bear,
i f t h e ir f r u i t s were n o t d e s ir a b le (3 8 , 39, 4 4 ).

P o itea u (44)

d isc u sse d th e a d v is a b ilit y of growing and g r a ftin g s e e d lin g t r e e s
in

th e n u rsery and then tr a n sp la n tin g to

t h e ir permanent p laces*

V arious w r it e r s (1 , 3 , 6 , 15,

16, 17, 26, 33, 34, 35,

38, 4 3 , 57) have favored th e c l e f t g r a ft and have d escrib ed t h e ir
p ro ced u res, which do not d if f e r e s s e n t i a ll y from th e method fo llo w ­
ed to d a y .

B a lt e t (7) a d v ise s th e c l e f t in a fo r k .
B e sid e s th e c l e f t g r a f t , K h i^ it (26) recommends th e

sadd le g r a f t .

B a lt e t (6.) recommends the bark g r a f t , which i s l a t e r

d escrib ed by M orris (37) as "New Method in G raftin g" , and a lso by
Biederman ( l l ) , Leroy (31) and o th ers (2 , 25) m ention th e claw
g r a ft,

s id e g r a f t , or g o a t’ s f o o t g r a f t ,

a s i t i s v a r io u s ly c a lle d .

V arious au th ors, B a lt e t (6) and o th e r s (1 0 , 55) have

4

s a id th a t th e E n g lish g r a f t , or as i t i s known in Am erica, whip
g r a f t , i s v ery s u it a b le fo r v e g e t a tiv e p rop agation o f th e P er­
s ia n w a ln u t.

Some recommend th e p la in whip and o th e r s the whip

w ith th e tongue to h o ld i t more c l o s e l y to g e th e r .'
In a d d itio n to the f lu t e bud, oth er methods o f bud­
d in g have been d escrib ed and a d v ised .

Some have sa id th a t the

s h ie ld bud, as commonly u sed w ith th e apple and th e peach, i s
a ls o a p p lic a b le to th e walnut (4 ); o th e r s (34) have denied i t s
s u i t a b i l i t y fo r the w aln u t.
The f l u t e bud, whereby a lo n g tube o f bark carryin g
buds was slip p e d o f f the cio n s t ic k and onto th e sto ck la id bare
by p e e lin g o f f the bark, has evolved by v a rio u s s te p s in to the
p atch bud*

I t f i r s t was m od ified in to th e r in g bud, c o n s is t in g

o f a p ie c e o f bark about an inch lo n g carryin g a bud b ein g removed
from th e c io n a s a r in g and p la ced on th e stock where a s im ila r
r in g had been removed*

T h is was con sid ered more s a t is f a c t o r y be­

cause i t did not n e c e s s it a t e the removal o f th e top o f th e stock*
U s u a lly , however, when the bud f a i l e d to u n it e , th e top o f the
sto ck died*

To avoid t h i s , i t became th e p r a c tic e to le a v e a s t r ip

o f bark o f th e sto ck in ta c t*

T h is l a t t e r was then c a lle d th e

"patch bud” and i s u sed very e x t e n s iv e ly in v e g e t a tiv e propagation
o f the pecan*

T his method has been advocated f o r the walnut by

Kraus ( 2 8 ), Lewis ( 3 3 ), Lake (2 9 ), O liver (42) and B atch elor (1 0 ),
and fo r th e pecan by Blackmon ( 9 ) , Reed (49 , 5 0 ), Evans ( 2 3 ), V/oolsey ( 6 1 ), and Woodard, Romberg and .V/iliman (6 2 ).

5

Kraus ( 2 8 ), Lake (29) and O liv er (42) su ggested a
m o d ific a tio n o f th e patch bud.

In stea d o f a path o f bark b ein g

removed from th e s to c k , an WI M cu t was made and the c io n patch
in s e r te d under th e two f la p s th us formed.
According t o Leroy (31) , B a tch elo r (10) and o th e r s
( 2 , 3 and 33 ) , g r a ftin g in th e crown, or r o o t , l e v e l w ith ground,
or s l i g h t l y below , o f f e r s much chance o f success*
th e u se o f th e o la w -fo o t, or the whip g r a f t ,

They su g g est

When th e g r a ft i s

made, s o i l i s mounded to near th e top o f the c io n .

It is d iffi­

c u lt to e v a lu a te r e p o r ts on crown g r a ftin g f o r some w r ite r s
( 3 , 4 , 6 , 40) r e f e r to g r a ftin g in the main branches o f la r g e r
t r e e s a s crown g r a ftin g , w h ile some, as Leroy (3 1 ), r e f e r to the
g r a ft p la c ed a t th e su r fa c e o f th e s o i l by t h i s term .
O arriere (15) d escrib ed a method which he d id not claim
as o r ig in a l and, 27 y ea rs l a t e r (1 6 ), which he a scrib e d to Treyve
as b ein g new and o r ig in a l.

In th e sp rin g b efo re th e development

o f le a v e s , January to March, young t r e e s are taken up, t h e ir tap
r o o ts cu t o f f and the t r e e s p la ced in 8 t o 10 cm. p o ts , which are
then plunged in a c o o l p la c e in th e garden.

I f no p o tted t r e e s

are a v a ila b le a t th e tim e o f g r a ftin g , th e t r e e s are grubbed,
g r a fte d and then p o tte d .

I t i s not f u l l y c le a r , from h i s d e sc r ip ­

t io n , a t j u s t what time o f th e year the a c tu a l g r a ftin g i s done,
but o th e r s (8 , 35) g iv e the tim e a s th e f i r s t p art o f March.

The

sto c k s are c l e f t g r a fte d near th e crown, th e g r a f t s bound and cov-

6

ered w ith wax*

A b e l l ja r i s then p la ced over than fo r th ree

weeks or a month*

VOien th ey b egin to grow, th ey are given a ir

g r a d u a lly t o harden them o f f .
O thers (6 , 8 , 1 7 , 35, 56, 60) have d escrib ed t h i s
method; some a d v ised th e u se of whip g r a ft in ste a d o f c l e f t ,
some adding minor p o in ts and some to ex p la in c e r ta in s te p s .
W itt (60) s a id i f bottom h eat o f 70° to 75° 3T. i s m ain tained,
union i s e f f e c t e d more r a p id ly .

Knight (26) used a method q u ite

s im ila r excep t th a t he does not m ention th e use o f a b e l l jar or
s im ila r apparatus.

H is id e a was p rim a r ily to reta rd th e growth

o f th e sto c k u n t i l cio n wood was s u it a b le fo r u s e .

He used cio n

wood o f th e current season* s growth.
W itt (60) s t a t e s th a t the Y/alnut can be propagated by
s o f t wood g r a f t s .

P otted p la n ts in th e greenhouse are g ra fted

w ith wood which i s about h a lf r ip e .

Cions are e it h e r the term in al

p o r tio n or a p ie c e w ith two e y e s , having h a lf o f th e l e a f su rfa ce
removed.

The g r a ftin g i s done by th e saddle or strap method.

He

a ls o says th a t s o f t wood c u t tin g s o c c a s io n a lly s tr ik e r o o t.
V arious ty p e s o f cio n wood have been used and a d v ised ,
in many c a s e s a p p aren tly from p erson al p referen ce based on in t e r ­
p r e ta tio n o f ex p erien ce.
De S erre (51) and o th e r s (24=, 34, 36, 4 4 ) , a d v isin g th e
u se o f the f l u t e bud, recommend cio n wood o f the p a st sea so n ’ s
growth, cut a f t e r growth had begun in the sp rin g and used immedi­
a te ly .

T h is, o f co u rse, was n ecessa ry in th e f lu t e bud.

Knight

7

(26 , 27) used wood o f th e cu rren t sea so n ’ s growth c o lle c t e d a f t e r
buds were w e ll formed.

He a ls o used wood o f th e p a st sea so n ’ s

growth, a llow ed th e buds to s w e ll and removed them, u sin g the sm all
secondary buds f o r c io n s .

He a ls o used the sm all buds from near

th e base o f one year wood,
P o ite a u (44) recommended c u ttin g cio n wood in February
and burying i t in s o i l to keep i t dormant.

C arriers (15) ad vised

th e u se o f c io n wood o f th e p a st sea so n ’ s growth, cut in January,
as d id M o r t ille t ( 3 8 ).

M ich elin (35) rep orted c io n s should be cut

e a r ly in March,
Leroy (3L) s ta te d th a t h is f i r s t su c c e ss in g r a ftin g
th e walnut was ob tain ed by u se o f wood two or th ree years o ld .

He

sa id th a t one year wood had r e l a t i v e l y more p ith than woody por­
t io n , w h ile the o ld e r wood had v ery l i t t l e p ith as compared w ith
wood,

B a lt e t (6) rep orted one year wood w ith a p o r tio n o f two year

wood a t i t s base to be s a t is f a c t o r y fo r u se as cion wood.

Another

w r ite r favored the wood a t th e ju n c tio n o f one and two year wood,
and Gaucher (25) shows a fig u r e i l l u s t r a t i n g t h is p r a c t ic e .
In the U nited S t a t e s , Cooper (20) d escrib ed good cio n
wood a s b ein g o f the p a st sea so n ’ s growth, cut in l a t e w in ter from
u p rig h t growing b ranches.
o f d e s ir a b le c io n wood:

Lake (29) gave th e fo llo w in g d e s c r ip tio n
"wood o f p ast sea so n ’ s growth which has

l i t t l e p it h , stro n g but not la r g e buds and firm wood, 1 /4 to 3 /8
inch in d iam eter, w ith short in te r n o d e s, taken from mid p o r tio n o f
trees.

Cut two or th r e e weeks before growth s t a r t s .

Dip cut ends

8

in wax, wrap in m o ist paper” .
E vidence on th e e f f e c t o f tem perature on g r a ft
u n ion s i s more e x te n s iv e than d e f in i t e .

The b e t t e r r e s u lt s

a tte n d in g l a t e , as c o n tr a sted w ith e a r l i e r , g r a ftin g , ra th er
fr e q u e n tly rep o rted , may be construed as u n co n scio u sly given
ev id en ce o f fa v o r in g e f f e c t s o f h igh tem perature.

The su c c e ss

o f th e Treyve method may be s im ila r ly in te r p r e te d ,
O liv er (41) d escrib ed a method fo llo w e d by W. P.
Corsa.

S to c k s, two y ea rs o ld , are cu t o f f ju st above th e junc­

t io n o f stem and r o o t s .

Cions are put on by any convenient

method, u s u a lly tongue or s p li c e , and s e c u r e ly t ie d .

The g r a f ts

are packed in la y e r s o f spaghnum and p laced where th e tem perature
i s m aintained from 75° to 80° F . , u s u a lly f o r th ree weeks.

The

g r a f t s are then p o tted and, when a few le a v e s have been made, the
p o tte d p la n ts are hardened o f f , and p la n ted in a frame where th ey
p a ss the f i r s t y ea r.

By t h i s method, about 75% "take” was secu red .

In t h is ca se a ls o , the tem perature was one o f th e p o s s ib le f a c t o r s .
Ravaz (48) rep orted experim ents on bench g r a ftin g o f
th e grape.

He found th a t below 20° C. union foim s very slo w ly ;

a t 2 2 °, i t i s more rap id ; and th a t i t i s extrem ely rap id in the
neighborhood o f 3 0 °.

He quoted Mazade to th e e f f e c t th a t the

b e s t tem perature seems to be from 30° to 35°•

At t h is tempera­

tu r e , th e e v o lu tio n o f sh o o ts i s prompt, th e t i s s u e s u n ite in 8
d ays, and the g r a fts can be removed from the m oist m a te r ia l.

Hu-

9

m id ity should be k ep t h ig h .
Most w r ite r s emphasize th e f a c t th a t the walnut i s very
d i f f i c u l t to propagate a s e x u a lly .

M o r t ille t (39) s ta te d th a t a

s k i l l f u l o p era to r can g e n e r a lly count on o n e -th ir d to o n e -h a lf o f
th e c io n s s e t l i v i n g .

K night (2 6 , 2 7 ), C a rriers (1 6 ), M ich elin

(35) and o th e r s , rep orted th a t asex u a l prop agation i s on ly r a r e ly
su c c e ss fu l*
EJCPERIMEINTAL METHODS.
¥/ork on th e v e g e t a tiv e prop agation o f th e b lack walnut
was begun in 1926.

At the o u t s e t , s in c e slow c a llu s f o m a t io n

seemed to c h a r a c te r iz e th e w alnut, th e c o n d itio n o f the reserv e
m a te r ia ls in th e c io n and stock was thought t o be p r im a r ily r e ­
sp o n sib le f o r th e wide v a r ia t io n s in th e degree o f su c c e ss ob­
ta in e d a t d iff e r e n t tim e s.

C onsequently, the f i r s t work c o n s is te d

o f an attem pt to m odify the sto red food m a te r ia ls w ith in the stem,
w ith th e aim o f o b ta in in g d iffe r e n c e s in behavior in g r a ftin g .
E a rly in the work, i t became apparent th a t oth er f a c ­
t o r s b e s id e s th e sto red food m a te r ia ls were o p e r a tiv e and p o s s ib ly
o f more im portance.

The work was th er e fo r e m od ified to in clu d e

oth er l i n e s o f in v e s t ig a t io n .
in th e fo llo w in g order:

These l i n e s are rep orted se p a r a te ly

( l) The in flu e n c e o f r e se r v e food sup p ly,

e s p e c i a ll y o f carbohydrates and n itro g en ; (2) The e f f e c t o f t r e a t ­
in g th e c io n s w ith ch em icals; (3) Propagation by budding; (4) The
in flu e n c e o f anatom ical c h a r a c t e r is t ic s ; (5) The in flu e n c e o f g ro ss
anatomy; (6) The in flu e n c e o f atm ospheric hum idity; (7) The i n f l u ­
ence o f tem perature.

10

1#

THE INFLUENCE OF RESERVE FOOD SUPPLY.
Oion Wood.

For t h i s s e r i e s o f exp erim en ts, c io n wood was ob tain ed
from a block o f se e d lin g , t r e e s in th e nursery o f th e F o r estry De­
partment o f the M ichigan S ta te C o lleg e a t E ast L an sin g.

These

t r e e s were about tw elv e y ea rs old at th e b egin n in g o f the e x p e r i­
m ent, 10 to 15 f e e t h i ^ i , m od erately v ig o r o u s, but not uniform .
Cion wood was s e le c t e d from th o se in the b est s ta t e o f v ig o r .
To secu re v a ried chem ical c o n d itio n s in wood d estin e d
fo r c io n s , sh o o ts were tr e a te d in f i v e ways.
A p art o f th e sh oots was l e f t in the n a tu r a l c o n d itio n ,
w ith out any treatm en t.

T his was d iv id ed in to two l o t s ; one l o t

was gathered in th e f a l l o f 1926 and the o th er l o t in th e spring
o f 1927.

These are d esig n ated " n a tu r a l-fa ll" and " n a tu ra l-sp rin g ” ,

r e s p e c t iv e ly .

Each o f th e se l o t s was subdivided in to f iv e c la s s e s :

1 , a p ic a l p o r tio n o f one year wood; 2 , b a sa l p o r tio n o f one year
wood; 3 , a p ic a l p o r tio n o f two year wood; 4 , b a sa l p o rtio n o f two
year wood; and 5 , a p ic a l p o r tio n o f th ree year wood.

C lass 4

corresponds to the l o t "Above g ird le" and c la s s 5 corresponds to
th e l o t "Below g ir d le " , as m entioned below .
A th ir d l o t was prepared in August, 1926, by tw is t in g
a w ire t i g h t l y around the stem a t th e base o f the two year wood.
The s ix in ch p o r tio n ju s t above t h i s w ire g ir d le was used as cio n
wood and c a lle d "Above g ir d le " .

The s ix inch p o r tio n j u s t below

th e w ire g ir d le was used as cio n and c a lle d "Below g ir d le " .

11

About th e same tim e a fo u rth l o t o f cion wood was p re­
pared by p a r t ly d e fo lia tin g *

The r a c h is o f th e compound l e a f was

sev ered so th a t approxim ately h a lf of the l e a f area was removed.
T h is l o t i s c a lle d " D e fo lia ted " .
T rees from which a f i f t h l o t o f c io n wood was c o lle c t e d
r e c e iv e d an a p p lic a tio n o f su lp h a te o f ammonia about th e m iddle o f
September, 1926, a f t e r growth had cea sed .

T h is did not cause a

resum ption o f growth, but th e t r e e s r e ta in e d t h e ir le a v e s l a t e r

in

th e f a l l than th o se not r e c e iv in g the treatm ent and began growth
e a r lie r th e fo llo w in g sp r in g .

T h is treatm ent i s d esign ated by th e

word " N itra te" .
For the c io n wood which was used in th e 1928 g r a ftin g ,
trea tm en ts were begun e a r li e r in 1927.

N itr a te o f soda was a p p li­

ed on J u ly 11 fo r th e "N itrate" cio n s and branches were g ir d le d
w ith w ire on Ju ly 18 f o r th e "Girdled" c io n s .
Cion wood from th e " N a tu r a l-fa ll" c la s s was gathered
December 11, 1926, and sto r e d , and cion wood f o r the "Naturalspring" and a l l oth er c la s s e s was gathered A p ril 6 , 1927, and
sto red u n t i l needed.
Cion wood fo r u se in 1928 was gathered e a r ly in May,
packed in saw dust, and p la ced in cold sto r a g e .

The sto ra g e did

n ot work w e ll and tem peratures were too h ig h , causing many o f th e
buds to s w e ll.
Samples fo r chem ical a n a ly s is were c o lle c t e d a t th e
tim e the c io n wood was c u t.

12

STOCK.
S e e d lin g t r e e s th a t were used f o r sto c k s onto which
were g r a fte d th e cio n wood p r e v io u s ly d escrib ed were lo c a te d in
th e n u rsery o f th e F o r e str y Department.

They were about f iv e

y e a rs o ld a t th e tim e the experiment was begun, and about fou r
f e e t h ig h .

Although a s a whole th ey were not uniform , i t was

p o s s ib le t o s e l e c t t r e e s th a t were f a i r l y uniform .

Some o f th e se

t r e e s were g ir d le d , some d e f o lia t e d and some f e r t i l i z e d as de­
sc r ib e d f o r th e c io n wood, excep t th a t in t h i s case th e w ire g ir d le was
p la ced around the main stem near th e ground.
GRAFTING.
In 1927, g r a f tin g was begun A p ril 25 and com pleted May
4 , and in 1928 i t was begun May 14 and com pleted May 25.

Various

com binations o f the tr e a te d and u n trea ted cio n s w ith the tr e a te d
and u n tr e a ted sto c k s were made.

These com binations, w ith th e p er­

cen t a ges o f s u c c e s s fu l u n ion s are p resen ted in T ables 1 and 2.
The whip, or tongue g r a f t , made in th e u su al way, was used in 1927;
th e sim ple s p lic e g r a ft and a few c l e f t g r a fts were used in 1928.
The cio n was f i t t e d to th e sto ck t ie d w ith a co tto n s tr in g and the
e n t ir e union and t i p o f c io n covered w ith a brush wax, made ac­
cord in g to a common form ula,

(1 4 ).

The e n tir e cio n and union were

covered w ith a k r a ft paper bag.
CHEMICAL,
Carbohydrate A n a ly sis .
Samples fo r chem ical a n a ly s is were cut in to h a lf inch

13

p i e c e s , w eighed, and p reserved "by d ryin g a t 90° C ., ground to
p a ss a 60-mesh s ie v e .

An a liq u o t o f th e dry ground m a teria l

was e x tr a c te d w ith f i v e 80 m l. p o r tio n s o f 80$ a lc o h o l.

A fte r

the l a s t e x t r a c tio n , th e r e sid u e was washed se v e r a l tim es w ith
80$ a lc o h o l.
The a lc o h o l was evaporated a t reduced p ressu re a t 50°
C. and th e r e sid u e

taken up w ith about 150 m l. w ater.

The ex­

t r a c t was c l a r i f i e d w ith le a d a c e t a te and deleaded w ith d ib a sic
sodium phosphate.

The reducing power o f an a liq u o t was determined

and exp ressed a s d e x tr o se .
The S h a ffe r and Hartraent io d in e t i t r a t i o n method was
used to determ ine th e red u cin g power.

D u p lica te d eterm in ation s

were made which checked t o 0 .1 m l. th io -s u lp h a te .
An a liq u o t o f th e c l a r i f i e d e x tr a c t was hydrolyzed
w ith 1 .5 $ HC1 fo r 10 m inutes at 70° C ., and th e reducing power
determ ined and exp ressed as t o t a l sugars.
The r e sid u e from th e a lc o h o l e x tr a c tio n was d ig e ste d
w ith ta k a -d ia s ta s e fo r 36 hours a t 38° 0 . , f i l t e r e d , and th e f i l ­
t r a t e hydrolyzed w ith 1 .8 $ H01 fo r S j hours.
was determ ined w ith ou t p rev io u s c l a r i f i c a t i o n .

The reducing power
From t h i s the

sta r ch co n ten t was c a lc u la te d .
‘The r esid u e from th e ta k a -d ia s ta s e d ig e s tio n was h y d ro l­
yzed fo r

h ou rs, w ith 1 .8 $ HC1, co o led , f i l t e r e d , and th e r e ­

ducing power determ ined.

From t h i s , c a lc u la tio n s were made f o r

14

a c id h y d ro lo za b le p o ly sa c c h a r id e s oth er than sta r c h , presumably
h e m i- c e llu lo s e .
NITROGEN ANALYSIS.
S o lu b le , in s o lu b le and t o t a l n itr o g e n were determined
by th e Experiment S ta tio n Chemist, u sin g th e Keldahl-Gunning
method.
PRESENTATION OF DATA.
The in flu e n c e o f the age o f cio n and th e time o f c o l ­
l e c t i n g c io n wood upon th e per cen t o f "take” in black walnut are
p re se n te d in Table 1 .

The cio n wood was n atu ral or u n tr ea ted ,

p a rt o f which had been cut in l a t e f a l l o f th e p reced in g season
and p a rt cu t a short tim e b efore growth commenced in sp rin g .
These were d iv id ed in t o th e ages and p o r tio n s as shown in th e
t a b le .

The sto ck was n a tu ra l or u n tr ea ted .
The data o f t h is ta b le c le a r ly in d ic a te th a t cio n wood

c o lle c t e d in the sp rin g i s much su p erior to th a t c o lle c t e d in the
fa ll.

T h is i s probably due to th e le n g th o f th e storage p eriod ;

p o s s ib ly some change in the stem, due to co n tin u a tio n o f r e s p ir a tio n
w ith out replenishraent o f m a te r ia ls i s r e s p o n s ib le .

Soane fu r th e r

o b se r v a tio n s in d ic a te th a t l o s s o f water from the stem i s a ls o a
f a c to r even though th e sh oots were packed in m oist m a te r ia l.
With both f a l l c o lle c t e d and sp rin g c o lle c t e d c io n s ,
the p er cen t o f "take" in c r e a s e s w ith in c r e a se in age o f wood.
The g r e a te r su c c e ss w ith o ld e r cio n wood m ight appear to be due
to th e s iz e o f the buds and the rea d in ess w ith which th ey b egin

15

to grow*

At each nod© on th e walnut u s u a lly th ree buds d evelop ,

th e more d i s t a l one b ein g la r g e and th e proxim al one v ery sm a ll,
o fte n i n v i s i b l e to th e unaided e y e .
th e s e i s an in ter m e d ia te s iz e .

Another bud lo c a te d between

Near th e d i s t a l end o f th e one

y ea r wood, the d i s t a l bud d evelop s to an ex ten t th a t makes i t
v e r y prominent and, during th e f o llo w in g growing sea so n , may grow
in to a shoot*

The la r g e r bud a t each node which does not produce

a shoot during th e second season u s u a lly a b s c is e s and o c c a s io n a lly
th e m ed ial bud a ls o a b s c is e s , e s p e c ia lly i f i t developed to a
n o tic e a b le s i z e .

On b earin g t r e e s , t h i s m edial bud fr e q u e n tly

produces stam inate flow ers*

The th ir d or sm aller bud a t each

node rem ains dormant u n t i l forced in to growth by am putation o f th e
shoot beyond, or some s im ila r stim u lu s.
The la r g e buds on th e one year wood, e s p e c ia lly th o se
on th e a p ic a l p o r tio n , fo r c e in to growth r e a d ily when t h i s p o r tio n
o f th e shoot i s used fo r c io n .

The r e s u lt in g growth e x e r ts a

demand fo r sto r e d m a te r ia ls which may d ep le te them to such an ex­
te n t th a t c a llu s fo n a a tio n does not tak e p la c e a t the cut end*
In t h i s p a r tic u la r experim ent such growth did not oc­
cu r, in f a c t , th e cio n d ied b efore any growth took p la c e .

L ater

experim ent s in d ic a te th a t the g rea ter xylem and phloem form ation
i s la r g e ly r e s p o n sib le f o r th e b e t te r r e s u lt s w ith o ld e r (and
la r g e r ) c io n s.
T h is s u p e r io r ity o f two and th ree year cio n wood was
ev id en t in a l l subsequent experim ents where one, tro and th ree year

16

sh o o ts were u se d .
Data showing th e in flu e n c e o f g ir d lin g th e sh oot, de­
f o l i a t i n g and a p p lic a tio n o f n itro g en o u s f e r t i l i z e r s are p resen ted
in T able 2 .

In t h i s t a b le , th e data are arranged to show th e in ­

flu e n c e o f th e s e trea tm en ts on th e c io n and, in Table 3 , the same
d a ta are arranged to show th e in flu e n c e o f the treatm en ts on th e
stock*
The p ercen tage o f "takert i s low in a l l in s ta n c e s but
th ere are some wide v a r ia t io n s .

In most c a s e s , th e s e v a r ia tio n s

d id n ot h old c o n s is t e n t ly fo r th e two years nor were th ey c o n s is ­
t e n t w ith in any one or more c la s s e s o f c io n or s to c k .
U sing the com bination o f n atu ral c io n on n atu ral stock
a s a b a s is o f com parison, th ere i s some evidence o f a p o s it iv e
in flu e n c e o f th e trea tm en t.

Three com binations o f cio n on stock

r e s u lt e d in an in c r e a s e in per ce n t o f "take" over the n a tu r a ln a tu r a l both y e a r s .

These are*, n it r a t e cio n on above g ir d le sto c k ,

above g ir d le c io n on above g ir d le sto c k , and above g ir d le c io n on
n it r a t e s to c k .

S ix com binations gave b e t te r r e s u lt s than th e

n a tu r a l-n a tu r a l one year and poorer r e s u lt s the oth er y ea r.

These

are: n a t u r a l- n it r a t e , above g ird le-b elo w g ir d le , above g ir d le n a tu r a l, below g ird le-a b o v e g ir d le , below g ird le-b elo w g ir d le ,
c io n -s t o c k , r e s p e c t iv e ly .

A ll oth er com binations were poorer both

y e a r s , or th e com bination was u sed on ly one y ea r.

17

Of a l l c l a s s e s o f c io n and s to c k , the most o u tstan d in g
r e s u l t s are w ith th e above g ir d le cip n and th e d e f o lia t e d c io n .
The above g ir d le c io n was used in fou r com binations and w ith two,
th e r e s u l t s were b e t t e r both y e a r s, and w ith two, the r e s u lt s were
b e t t e r one y ea r when compared w ith th e u n treated c io n .

The d e f o l­

i a t e d c io n was used o n ly one year b u t, in every com bination, r e s u lt s
were poorer than th e n a tu r a l c io n gave.

In th ree o f fo u r combina­

t i o n s , th e n it r a t e cio n gave poorer r e s u lt s both years and in th e
>o th e r b e t te r r e s u l t s both years than th e n a tu r a l c io n .
Carbohydrate and n itro g e n a n a ly s is o f the sh o o ts used
f o r c io n s and o f the sto ck are p resen ted in Table 4 , to g eth er w ith
th e p er ce n t o f ttta k e M secured when used fo r g r a ftin g .

In most c a s e s,

th e l a t t e r are averages o f the r e s u lt s o f each c la s s o f cio n on a l l
c l a s s e s o f sto ck used and o f each c la s s o f stock w ith a l l c la s s e s
o f c io n s .
Data f o r n a tu ra l cio n show a g en era l in c r e a se in p er cen t
o f su c c e ss w ith an in c r e a se in t o t a l carbohyd rate-nitrogen r a t i o , but
th e r e i s n ot a d e f in it e c o r r e la t io n .

Data fo r stock show a gen eral in ­

v e r s e r e la t io n s h ip ,t h a t i s , a d ecrease in su c cess w ith an in crea se in
th e r a t i o .
TABLE 1 .

INFLUENCE OF AGE OF CION AND TIME OF COLLECTION ON RESULTS
OF WALNUT GRAFTING-, 1927. NATURAL CION ON NATURAL STOCK.

Age o f cio n
T ears
1
1
2
2
3

P o r tio n o f
annual growth.
A p ica l
B a sa l
A p ica l
B asal
A p ica l

P ercentage "take”.
F a ll c o lle c t e d . Spring c o lle c t e d .
0
0
0
21.7
2 0 .0
3 3 .3
9 .1
3 1 .6
3 0 .8
5 2 .7

TABLE 2*

Cion

INFLUENCE OF GIRDLING, DEFOLIATING AND NITROGENOIB FERTILIZERS UPON THE WALNUT CION VffiEN
USED IN GRAFTING.

Stock

P ercentage "take”
1927
1928

R e la tiv e
Behavior

Order tv/o
years combined

N atu ral N atural

3 9 .2

3 2 .0

100.0

1 00.0

4

N itr a te

3 6 .8

4 6 .0

9 3 .8

1 43.7

5

Above g ir d le

-

1 2 .2

-

3 7 .5

18

Below g ir d le

-

3 0 .4

-

9 5 .0

14

N itr a te N atural

3 7 .5

3 0 .4

95.6

9 5 .0

11

N itr a te

3 3 .3

2 6 .0

8 5 .0

8 1 .2

12

Above g ir d le

5 8 .8

32 .0

150.0

100.0

1

Below g ir d le

-

1 7 .4

-

5 4 .4

16

26.7

34 .8

70.0

108.7

7

4 0 .0

3 2 .2

102.0

100.6

3

130.0

2

Above
N atural
g ir d le
N itr a te
Above g ir d le

4 0 .0

•
«—
I

102.0

Belov/ g ir d le

6 1 .6

24.0

157.1

75.0

6

37.5

4 .2

95 .6

13.1

13

-

5 5 .5

—

173.4

10

Above g ir d le

1 5 .4

4 4 .0

3 9 .3

137.5

8

Below g ir d le

20.0

4 3 .5

50.9

136.0

9

3 3 .3

-

8 5 .0

-

*5

Above g ir d le

1 2 .5

-

32.0

-

20

Belov/ g ir d le

13-0

-

33 .1

-

19

D e fo lia te d

20.0

_

17

Belov/
N atural
g ir d le
N itr a te

D e fo lia te d N atural

50 .9

TABLE 3 .

Stock

INFLUENCE OF GIRDLING, DEFOLIATING AND NITROGENOUS
FERTILIZERS UPON THE STOCK OF WALNUT WHEN USED IN
GRAFTING.
Gion

P ercen tage "take”
1927

1928

R e la tiv e Behavior
on b a s is of
n a tu r a l on n a tu ra l
1927
1928

N atu ral N atural

3 9 .2

32.0

100.0

1 00.0

N itr a te

3 7 .5

3 0 .4

9 5 .6

9 5 .0

Above g ir d le

26 .7

3 4 .8

70.0

1 08.7

Below g ir d le

3 7 .5

4 .2

9 5 .6

1 3 .1

N itr a te N atu ral

3 6 .8

4 6 .0

9 3 .8

143.7

N itr a te

3 3 .3

2 6 .0

8 5 .0

8 1 .2

Above g ir d le

4 0 .0

3 2 .2

102.0

1 00.6

Below g ir d le

-

5 5 .5

-

1 7 3 .4

-

1 2 .2

-

3 7 .5

5 8 .8

32.0

150.0

1 00.0

Above g ir d le

40 .0

4 1 .6

102.0

130.0

Below g ir d le

1 5 .4

4 4 .0

39.3

137.5

-

3 0 .4

-

95.0

-

1 7 .4

-

5 4 .4

Above
g ir d le
Below g ir d le

61 .6

24.0

157.1

75.0

2 0 .0

43 .5

5 0 .9

136.0

D e fo lia te d

20.0

N atural
Above
g ir d le
N itr a te

Below
N atural
g ir d le
N itr a te

D e fo li
ated

50 .9

Starch

H em i-cellulose

Total carbo­
hydrate s

Total

N a tu r a l-F a ll
A p ic a l- 1 y r.
B a s a l- 1 ”
A p ic a l- 2 "
B a s a l- 2 ,f
A p ic a l- 3 "

4 9 .6
5 1 .8
5 4 .0
5 4 .8
-

4 .9 2
4 .6 9
4 .4 5
3 .9 0
6 .9 5

1 .9 5
1.46
1.40
2.4 8
1 .4 8

1 3 .0 5
1 1 .9 3
1 1.79
9 .8 3
1 4.41

1 9 .9 2
18.08
1 7 .6 4
1 6 .2 2
2 2.84

1 .2 9
.80
.6 2
.7 4
.70

15.46
22.60
28.45
21.92
32.63

0
0
20
9
31

N a tu ra l-S p ri ng
A p ic a l- 1 y r.
B a s a l- 1 "
A p ic a l- 2 "
B a s a l- 2 "
A p ic a l- 3 ,f

4 8 .2
5 4 .1
5 7 .4
5 4 .4
5 2 .7

2.9 1
2 .5 0
4 .3 0
3 .6 7
2.7 9

1 .1 8
.38
1.9 1
.97
1.1 5

1 3 .7 2
1 1 .8 1
13.05
1 2 .0 4
11 .2 5

17.81
14.69
1 9.26
16.68
15.19

1 .3 4
.77
.73
.7 5
.6 4

13.29
19.08
26.38
2 2 .2 4
23. 73

0
22
33
32
53

Above g ir d le
Below g ir d le
D e fo lia te d
N itr a te

51 .9
52 .9
54 .8
5 4 .1

2.3 5
2.57
3 .2 0
2 .9 7

2.7 5
.91
.98
.98

12.49
11.81
12.38
11 .7 4

18.59
15.29
15.56
15. 74

.72
.63
.5 2
.87

2 5.82
24.27
31 .8 4
18.09

41
25
19
42

Stock
N atural
N itr a te
Above g ir d le
Below g ir d le
D e fo lia te d

57 .6
5 3 .1
5 8 .1
5 7 .1
5 6 .2

5 .0 8
3 .5 2
6 .2 5
4 .5 3
5 .4 1

1 .5 6
1 .9 1
1 .6 5
1 .5 6
1 .1 2

12.38
13.61
14.29
14.41
12.04

1 9 .0 2
1 9 .0 4
22.19
20.50
18.57

.6 4
.6 4
.60
.56
.53

29.72
29.75
3 6 .9 8
36.61
35.02

39
37
32
32
20

sugars

o

[ Dry m atter

Total

nitrogen

TABLE 4 . CARBOHYDRATE AND NITROGEN ANALYSES OF CION WOOD AND
___________ STOCK IN PERCENTAGES AND FIELD RESULTS, 1927._______

c
©
■3

Eh

18

The c io n s tr e a te d by g ir d lin g , d e f o lia t io n and n itr o g ­
enous f e r t i l i z e r s do not show a c o r r e la t io n e it h e r w ith , or in v e r s e ­
l y t o , th e carbohydrate r a t io .
In r e s p e c t to n itro g e n a n a ly s is , th e n a tu ra l c io n shows
s u c c e ss in v e r s e ly to th e per cent n itr o g e n .

The tr e a te d c io n

and

th e sto ck show su c c e ss in c r e a s in g w ith th e in cr e a se d per cent n i ­
tro g en .
In r e s p e c t to t o t a l sugar, sta r c h , h e n i- c e llu lo s e and
t o t a l carb oh yd rates, no d e f in it e r e la t io n s h ip to th e p er cent o f
s u c c e ss can be d isco v er e d .
These data do not show any o u tsta n d in g in flu e n c e upon
s u c c e ss in g r a f tin g , nor in carb oh yd rate-n itrogen a n a ly s is ,a s a
r e s u lt o f th e trea tm en ts of the sh o o ts.
The method o f a n a ly s is f o r carbohydrates i s open to
c r it ic is m in th a t th e sample was d ried a t a tem perature which was
to o high*

The tim e o f sam pling i s a ls o a t f a u lt in th a t samples

were taken a t the tim e th e c io n wood was c o lle c t e d .

Behavior of

c io n s upon g r a ftin g in d ic a t e s th a t th e sample probably would have
been more n e a r ly r e p r e s e n ta tiv e had i t been taken a t th e tim e the
g r a ftin g was done.
E3CPSRIMEDTS OF 1931.
Further work on th e in flu e n c e o f sto red food m a te r ia ls
7/as

postponed u n t i l c e r ta in oth er

f a c to r s could be worked o u t,

p r in c ip a lly the in flu e n c e o f tem perature.

Having t h i s worked o u t,

i t was d ecid ed t o rep ea t a p o rtio n o f th e e a r l ie r exp erim en ts.

19

September 3 and 4 , 1930, c io n wood on walnut t r e e s o f
Mr. W. J . F u l l i l o v e , S h revep ort, L o u isia n a , was prepared.

Branches

were rin g ed in th r e e year o ld wood and the wound was covered to
p r o te c t I t from d ryin g o u t.

T his cio n wood was c o lle c t e d February

2 , 1931, and packed in m o ist spaghnum m oss, and was l a t e r used to
make g r a f t s , b ein g p la ced on two year o ld s e e d lin g r o o ts near th e
ju n c tio n o f th e stem and r o o t .

The g r a f tin g was com pleted on

February 7 .
One hundred g r a f ts o f each o f the fo llo w in g s e r ie s were
made:

( l ) b a sa l p o r tio n o f one year wood from g ir d le d stem , (2)

two year wood from g ir d le d stem , (3) th r e e year wood from g ir d le d
stem , which was cut so t h a t th e b ev el was ju s t above th e g ir d le
u s u a lly c u t tin g through a p o r tio n o f th e en larged stem which was
stim u la ted by th e g ir d le , (4) b a sa l p o r tio n o f one year n a tu ra l
stem ,

(5) two year wood o f n a tu ra l stem , (6) th ree year wood o f

n a tu r a l stem .

F i f t y g r a f ts were made -of th e p o r tio n im m ediately

below th e g i r d l e .
These g r a f t s were packed in m oist p eat and p laced in
boxes w ith temperature c o n tr o lle d a t 26°-28° G.
th e boxes f o r th r e e weeks and then examined.

They were l e f t in

A fte r the exam ination,

th e g r a f t s were again packed in m oist peat and p la ced on th e south
s id e o f a b u ild in g , w ith th e tem perature u n c o n tr o lle d , to a llo w
them to grow.

They w efe examined on A p ril 25 and count made o f

th o se a c t u a lly growing.

R e s u lts are p resen ted in Table 5 .

20

TABLE 5 .

INFLUENCE OF AGE OF SHOOT AND GIRDLING UPON THE BE­
HAVIOR OF CION WOOD OF THE WALNUT UPON GRAFTING,
GRAFTS EXPOSED TO TEMPERATURE OF 26°-28° C. FOR 21
DAYS.

C la ss o f c io n wood

C allu sed
February 27, 1931.

Growing
A p ril 25, 1931.

1 year n a tu r a l

89

76

2 y ea r n a tu r a l

90

89

3 year n a tu r a l

87

90

1 year above g ir d le

81

77

2 year above g ir d le

92

86

3 year j u s t above g ir d le

88

88

J u st below g ir d le

82

70

There i s a s t r ik in g ly h ig h er p er cen t o f g r a f ts grow­
in g w ith a l l c l a s s e s o f cio n wood than had p r e v io u s ly been secured
when th e tem perature was not c o n tr o lle d .
With both the n a tu ra l sh oots and th e g ir d le d sh o o ts,
th e re i s an in c r e a s e In th e per cent growing w ith in c r e a se in age,
but t h i s in c r e a s e i s n ot as great in the g ir d le d wood a s in th e
n a tu ra l wood.

Cion wood from below

th e g ir d le gave very markedly

poorer r e s u lt s than any o th er c l a s s .
2.

TREATMENT OF CIONS WITH CHEMICALS.

Treatment o f c u ttin g s w ith chem icals has been found by
C u r tis (22) and o th e r s ( 2^ and 59)

to in c r e a se th e

r o o tin g in some s p e c ie s .

i s r e a liz e d th a t r o o tin g o f

Though i t

p ercen tage o f

c u t t in g s and c a l l u s form ation are not u s u a lly a s s o c ia t e d , i t was

21

though t th a t s im ila r treatm en ts m ight in c r e a se c a llu s form ation
and th e u n itin g o f g r a f t s .

Cooper (20) s t a t e s th a t d ip p ing cut

c io n s in to ,a n d w ashing th e cut sto ck w ith*a s o lu t io n o f four t e a ­
spoons o f su lp h a te o f q u in ine to a g a llo n o f w ater w i l l r e s u lt in
90$ w alnut g r a f ts grow ing.
On May 25, 1928, n a tu r a l c io n s were cut as fo r g r a f t ­
in g and some were im m ediately p la ced in "beakers c o n ta in in g r e ­
s p e c tiv e ly : a 0 .5 $ s o lu tio n o f potassium permanganate, a 0 .5 $
s o lu t io n o f su c r o se , a 2$ s o lu tio n o f su c ro se, a 2$ s o lu tio n o f
d e x tr o se , a 5$ s o lu tio n o f v in eg a r, a 2$ s o lu tio n o f potassium
n i t r a t e , a sa tu ra ted s o lu tio n o f quinine su lp h a te, about 0 .1 4 $ .
One l o t was p la ced in d i s t i l l e d w ater, one l o t exposed to fumes
o f e th e r , and one l o t l e f t u n treated and cut and im m ediately
g r a fte d or p la ced in th e greenhouse bench.
The c io n s were allow ed to remain in th e se s o lu tio n s
f o r 24 hours w ith th e e x cep tio n o f the quinine s o lu tio n in which
th ey remained two h ou rs.

A p o r tio n o f the tr e a te d c io n s , w ith

check, was p la ce d in clea n sand in th e greenhouse bench and the
rem ainder were g r a fte d by th e whip g r a ft method onto sto c k s in
the n u rsery a s d escrib ed e a r lie r .
C a llu s form ation on c io n s in the greenhouse was not
m a te r ia lly improved; 13$ o f th e check and 19$ o f th o se tr e a te d
w ith p otassium permanganate and 21$ o f th ose tr e a te d w ith 2$
su cro se formed c a l l u s , w h ile a l l oth er c io n s f a il e d to form c a l­
lu s .

The r e s u lt s o f the g r a ftin g were sim ila r ; 25 per cent of

th e ch eck s, 15 per cen t o f th o se tr e a te d w ith potassium perman-

22

g a n a te, and 16 p er cen t o f th o se tr e a te d w ith q u in in e formed suc­
c e s s f u l u n ion s w h ile a l l o th e r s f a i l e d .
These r e s u l t s were from a ra th er lim it e d t r i a l , but
th ey in d ic a te th a t none o f th e treatm en ts t r i e d gave enough improve­
ment in c a l l u s form ation or union in g r a ftin g to warrant t h e ir u s e .
In another s e r ie s o f experim ents, th e beakers c o n ta in ­
in g the s o lu t io n s and c io n s were p la ced in a chamber which was
evacuated by u se o f a f i l t e r pump.

T h is removed a ir from the cio n

and th e s o lu t io n was drawn up in to th e stem s.

C onsiderable q u a n ti­

t i e s o f th e ch em icals were probably fo rced in to th e stem s.

R e su lts

from t h i s s e r ie s were in general agreement w ith th e f i r s t experiment
in th a t no in c r e a s e in per cen t o f s u c c e s s fu l unions v^as o b ta in ed .
3.

PROPAGATION BY BUDDING.

In May, 1927, about 150 buds o f named v a r i e t i e s were s e t
and in June, 1928, about 500, some o f named v a r i e t i e s and some from
g ir d le d and d e f o lia t e d c io n s were s e t .
The patch bud method d escrib ed by Kraus (28) was used
in s e t t in g some and th a t d escrib ed by Stueky and Kyle (53) fo r pecans
used in s e t t i n g o th e r s .

A m o d ific a tio n o f the budding k n ife de­

scrib e d by th e l a t t e r under th e name o f "Texas Agie" was used in a l l
th e budding.

The m o d ific a tio n c o n s is te d o f th e removal o f th e han­

d le p rovid ed , making a t o o l th a t could be h eld in th e palm o f the
hand and th e r e fo r e was more conven ient to h an d le.
T h is budding was not done on a c o n tr o lle d experim ental

23

b a s is , but t h e r e s u l t s are r a th e r in te r e s tin g #

T ab les 6 and 7

p r e se n t th e r e s u l t s o f the 1928 s e r ie s o f budding#
The bud wood o f the S ta b le r v a r ie t y was cu t about
s ix weeks b efo re th e tim e o f budding, w h ile th a t o f th e oth er
v a r i e t i e s was cu t ju s t b efo re growth s ta r te d , about two weeks
b e fo r e i t was used*

The S ta b le r and Ohio bud wood was not in the

b e s t o f c o n d itio n and i t was d i f f i c u l t to g e t the patch w ith th e
bud sep arated from the bud s t ic k w ith out in ju r in g th e growing
p o in t o f th e bud#

The o th er v a r i e t i e s were not id e a l in t h is r e ­

s p e c t, but th ey wdre much su p erio r to the S ta b le r and Ohio#

The

e f f e c t o f h aying s u it a b le bud wood i s c le a r ly e v id en t in the r e ­
s u lts #
Another p o in t o f in t e r e s t i s the d iffe r e n c e in th e
ta k e o f S ta b le r on b lack walnut sto ck s No# 1 and No# 2#

The n u ts

from which sto ck No# 1 were produced germ inated p o o rly and the seed­
l i n g s have grown s lo w ly , showing a l l appearance o f poor v ig o r . Those
seed from which sto ck No# 2 were produced germ inated w e ll and a
stand o f about 90 p er cen t was secu red .
w e ll and appear vigorous#

These s e e d lin g s have grown

The p ercen tage o f l i v i n g p a tch es i s sm all­

er on sto ck No. 1 and th o se which d id l i v e w efe slow er in producing
sh o o ts than on sto ck No# 2 .

The average le n g th o f growth on sto ck

No# 1 , on August 8 , 1928, was about s ix in ch es (Fig# 1 ) , w h ile th a t
on No# 2 was about 18 in c h e s (F ig , 2 ) .

Furthermore, a g rea ter

p ro p o rtio n o f th e l i v i n g p a tch es produced sh oots on sto ck No# 2#
Figure 2 shows the Kinder v a r ie t y but i s t y p ic a l o f a l l v a r i e t i e s

TABLE 6 . WALNUT BUDS SET AT GRAHAM STATION, GRAND RAPIDS,
___________ JUNE 1 , 1928, RECORD AUGUST 8 , 1928.____________
V a r ie ty

Stock

Buds s e t

Producing
sh o o ts

%

Patch
T otal
l i v i n g not p a tch es
producing l i v i n g
sh o o ts
io

%
S ta b le r

J* n ig r a No. 1

49

10.2

18.4

28.6

!f

"

50

30.0

20.0

50.0

ft

J . c in e r a

12

25.0

33.4

58.4

S ta b le r
g ir d le d
Thomas

J . co rd ifo rm is

32

21.9

18.7

40.6

J. n ig r a No. 2

20

60.0

35.0

95.0

Kinder

”

"

No. 4

25

76.0

4.0

80.0

Ohio

n

”

No. 4

15

46.0

6 .7

54.4

M ille r

"

"

No. 4

21

57.2

14,3

71.5

158

23.4

18.9

42.4

94

61.7

15.9

77.6

*

No. 2

T o ta l S ta b le r and Ohio
T o ta l o th er v a r i e t i e s
TABLE 7 ,

Bud Wood

J. CORDIFORMIS BUDDED ON J . NIGRA AT EAST LANSING IN 1928.

Buds s e t

Producing
sh o o ts
io

Patch l i v i n g
not producing
shoot S io

T otal p a tch es
liv in g %

N atural

13

6 1 .5

23.0

8 5 .0

G irdled

14

1 5 .4

5 0 .0

64*4

N itr a te

13

4 6 .2

1 5 .3

61,5

N it r a t e
g ir d le d

26

23.1

19*3

4 2 .4

24

on t h i s s to c k .
T able 7 g iv e s the r e s u lt s o f budding done on b lack
w alnut

u s in g c io n s o f Ju glan s co rd ifo rm is

which had p r e v io u s ly

been tr e a te d t o m odify t h e ir chem ical com p osition .

H alf o f a

row o f two year o ld s e e d lin g s were f e r t i l i z e d h e a v ily w ith n i­
t r a t e o f soda on J u ly 1 1 , 1927.

On August 9 , a lte r n a te t r e e s o f

both th e f e r t i l i z e d and th e u n f e r t il iz e d were g ir d le d ju s t a t th e
su rfa ce o f th e ground by t w is t in g a w ire t i g h t l y around th e stem .
These trea tm en ts gave fo u r c la s s e s o f c io n wood: 1 , n a tu r a l; 2,
g ir d le d ; 3 , n itr a te d ; and 4 , n itr a te d and g ir d le d .

Buds from

th e s e c io n s were s e t in b lack walnut sto c k .
R e s u lts show th a t th e u n trea ted c io n s gave b e st r e ­
s u l t s and th a t any treatm ent seems d etrim en ta l.

G ird lin g d ep ress­

ed th e p ercen tage o f l i v i n g p atch es and delayed th e shoot growth.
Presum ably, th e g ir d lin g and f e r t i l i z e r treatm en ts r e s u lt in de­
velopment o f th e bud tr a c e and growing p oin t to the p o in t th a t
removal o f th e bud from th e bud s t ic k o fte n in ju r e s th e growing
p o in t o f th e bud.
In th e sp r in g o f 1929, a th ir d s e r ie s o f budding
was done.

On A p r il 5 , 1929, one year o ld and two year o ld cio n

wood was cut and d iv id ed in to th r e e l o t s each.

One l o t was

covered co m p letely w ith m elted p a r a ffin , a second l o t had th e
cu t ends o n ly waxed, w h il th e th ir d l o t was not waxed.

On A p ril 30,

25

a second l o t o f c io n wood was cut and tr e a te d s im ila r ly #

On

June 1 , a l o t o f c io n wood was cu t fr e s h and buds from i t and
from a l l o f th e tr e a te d c io n s were s e t on th a t date#
Cion wood waxed com p letely i s d i f f i c u l t to han d le.
P a tch es o f bark are hard t o remove from th e stem because
csm bial a c t i v i t y i s d ep ressed and because th e wax makes i t d i f ­
f i c u l t to secure a firm g rip on th e c io n .

C ions which had not

been waxed had s u ffe r e d s l i g h t l y from d e s ic c a tio n and th e bark
did not s l i p as r e a d ily a s i s d esira b le#

Cions which had the

cut ends o n ly waxed were in e x c e lle n t con d ition #

The bark was

plump and fr e s h lo o k in g , and i t sep arated r e a d ily from th e
wood#
In a l l c a s e s except one, the c io n wood which had
o n ly th e cut ends waxed gave much b e t t e r r e s u lt s than the oth er
c la s s e s .

Cions waxed e n t ir e ly gave s l i g h t l y b e t te r r e s u lt s

th an th e c io n s n ot waxed but th e a d d itio n a l tim e req u ired to
lo o se n th e se buds frcm th e bud s t ic k w i l l more than o f f s e t the
advantage gain ed .
Cion wood cut June 1 had s ta r te d to gro?/ s l i g h t l y
and i t was d i f f i c u l t to remove th e p atch es of bark w ithout
in ju r in g the growing p o in t.

Probably had t h is wood been taken

a week e a r l i e r b a tte r su c c e ss would have been secured#

26

TABLE 8 .
D ate c io n cu t

A p r il 5

A p r il 30

June 1

RESULTS OF BUDDING DONE IN SPRING OF 1929.
Age o f wood
y ea rs

Waxing

Per cen t l i v i n g

1

none

91

1

ends

90

2

none

36

2

ends

75

2

a ll

60

1

none

69

1

ends

100

1

a ll

87

2

none

64

2

ends

82

2

a ll

75

1

none

44

These more or l e s s p relim in ary t r i a l s in d ic a te
th a t th e tim e o f budding i s v ery im portant.

Budding done soon

a f t e r growth began d id not g iv e n e a r ly a s good r e s u lt s as
budding done th r e e weeks l a t e r , when th e le a v e s
were about o n e -th ir d m ature.
a ls o im portant.

on th e sto ck

The c o n d itio n o f th e bud wood i s

The cambiura must be in an a c tiv e c o n d itio n to

perm it th e bark t o ”s lip " from th e sto ck , but th e bud must not

27

have become a c t iv e t o th e e x te n t th a t th e growing p o in t i s l i k e l y
t o be in ju r ed during th e budding p r o c e s s.
I f th e bud tr a c e o f th e bud s e le c t e d developed to th e
p o in t th a t any g rea t p o r tio n o f i t becomes l i g n i f i e d , i t w i l l be
d i f f i c u l t to remove th e bud w ith ou t in ju r in g i t .

T h is i s the con­

d it io n o f m ost o f th e la r g e r buds on t h e d i s t a l h a lf o f a tw ig o f
th e p reced in g y e a r ’ s growth.

The b e st buds f o r u se are u s u a lly

found a t th e proxim al end o f th e p reced in g y ea r’ s growth, or at th e
proxim al end o f two year o ld wood.

On th e two year o ld wood, th e

buds may o fte n be so sm all a s to be alm ost in v is ib le *

These buds

are th e ones th a t were formed l a s t o f the two or th r e e th a t occur
in each l e a f a x is , th e la r g e r ones formed e a r lie r having shed.

Such

buds are u s u a lly s a t is f a c t o r y fo r u se in p rop agating by th e p atch
method.
The method d escrib ed by Kraus (28) i s u n s a t is f a c t o r y
in th e b lack walnut fo r se v e r a l rea so n s.

To secu re good r e s u lt s

by budding, i t i s n ec essa ry th a t th e bud be p ressed fir m ly a g a in st
th e wood o f th e sto c k .

The two f la p s o f bark frcm th e stock s e r i ­

o u s ly in t e r f e r e and p ressu re o f the bud a g a in st th e stock i s n ot
secu red , which means th a t th e un ion between th e growing p o in t o f
th e bud and th e sto ck w i l l be delayed and may e n t ir e ly f a i l (F ig s .
3 and 4 ) .

A second o b je c tio n i s th a t th e v e r t i c a l cut on th e sto ck

u s u a lly comes d i r e c t l y under the growing p o in t o f th e bud.

The

28

in ju r y to th e c e l l s on th e sto ck may prevent th e form ation of
c a l l u s t is s u e from th e sto ck and th u s d ela y or p reven t u n ion .
F igu re 5 shows th e normal u n itin g of the reg u la r
patch bud and Figure 6 shows a ca se in which th e s h ie ld u n ite d
w e ll but th e bud f a i l e d to grow because the growing p o in t was
in ju red in th e tr a n s fe r .
4.

THE INFLUENCE OF ANATOMICAL CHARACTERISTICS.
S e c tio n s were made from s u c c e s s fu l and u n su c c e ssfu l

g r a f t s and from pruning wounds which had begun to h e a l.

Fresh

m a te r ia l was s e c tio n e d on a s lid in g microtome s e t to cu t 20 m i­
cro n s.

They were sta in e d by a m o d ific a tio n o f a method d escrib ed

in Turtox News:

s e c tio n s were p laced in an a lc o h o lic s o lu tio n o f

sa fr a n in fo r 30 m inutes to s e v e r a l hours.

They were d esta in ed in

a c i d i f i e d 50$ a lc o h o l and tr a n sfe r r e d to 50$, 70$, 95$ and abso­
l u t e a lc o h o l, rem aining in each on ly a few m in u tes.

They were

p assed thru 75$ x y lo l in a b so lu te a lc o h o l in to x y l o l in vfoich a
sm all amount o f g en tian v i o l e t was d is s o lv e d , allow ed to remain
th e r e u n t i l th e c e l l u l o s e t is s u e was sta in e d , then tr a n sferred t o
pure x y lo l and mounted in balsam.
The most s t r ik in g a sp ect o f s e c tio n s o f walnut g r a fts
(F ig u res 7 and 8) i s th e la r g e s iz e and number o f v e s s e l s , and o f
th e la r g e p ro p o rtio n o f th e o ld xylem t is s u e which i s dead.

The

v e s s e l s had not become plugged w ith gum as i s common in the t is s u e
o f th e p ear (F igu re 9) and apple (F igure 1 0 ), p o s s ib ly because the

29

wood d ie d to o r a p id ly .

Rapid k i l l i n g o f apple wood i s ch a ra cter­

iz e d by absence o f wound gum*
S e c tio n s o f prunissg wounds on w alnut stem s (Figs* 11,
and 12) show some degree o f c lo su r e o f v e s s e l s but a much g r e a te r
c lo su r e o f tr a c h e id s and v a sc u la r ray c e lls *

The rays and tr a c h e id s

seem to be c lo s e d by p lu g g in g w ith some gum l i k e su b stan ce, th e
n atu re o f which h as n ot been determ ined (Fig* 1 3 ) .

Some o f th e

v e s s e l s are c lo se d by t y l o s e s (F ig . 14) which occur in wood formed
a f t e f the wound i s made as w e ll as in wood a lread y p resen t a t th e
tim e o f th e wound.

In th e s e c tio n s examined no t y lo s e s have been

found in wood o ld e r than two y e a r s .

F igu re 14 shows r e l a t i v e l y

g r e a te r p ro p o rtio n o f v e s s e l s having t y lo s e s than i s t y p ic a l fo r
t i s s u e s n ot stim u la ted by wounds.
A pparently, th e u n itin g o f walnut g r a f ts i s not h in d er­
ed or lim it e d by the i n a b i l i t y o f the new growth t o change d ir e c ­
t io n s .
growth.

F ig u r e s 11 and 15 show the change in o r ie n ta tio n o f new
F igu re 11 i s a r a d ia l s e c tio n o f a stem o f walnut which

was amputated to a l a t e r a l branch.

The new growth i s su p p lied by

th e l a t e r a l branch a t an a n g le o f 90° from th e p lane

of th e s e c t io n .

The v e s s e l s in th e new wood are cut alm ost tr a n s v e r s e ly , in d ic a tin g
th a t the d ir e c t io n o f flow o f sap had changed.

F ig u res 7 and 8 show

s im ila r r e a c tio n s in th e growth su cceed ing the union o f a g r a f t.
The d i f f i c u l t y in g r a ftin g w aln u ts, from an anatom ical
sta n d p o in t, seems to be due t o th e f a c t th a t a c t iv e d iv is io n o f th e
cambium c e l l s w ith th e r e s u lta n t form ation o f wound parenchyma i s

30

lim it e d , e s p e c i a ll y in th e c io n .

T his d ela y in th e form ation o f

wound parenchyma seems to be due to a la r g e ex ten t to th e f a ilu r e o f
th e v e s s e l s to become p lu gged , th u s a llo w in g e x c e s s iv e l o s s o f
w a ter.

In a d d itio n , th e ray c e l l s and tr a c h e id c e l l s do become

plugged making t r a n s lo c a tio n o f sto red m a te r ia ls and w ater to the
cambium d i f f i c u l t .

P r ie s t le y (45) and P r ie s t ly and Swingle (46)

advance th e th eo ry th a t a h igh w ater co n ten t in th e cambium and
th e a d jo in in g c e l l s i s n ecessa ry b efo re a c t iv e growth can take
p la c e .

T h is th e o ry seems to help e x p la in th e slow ness o f the

w alnut to form wound parenchyma.
The union o f sto c k and cio n in g r a ftin g i s th e r e s u lt
o f th e m eetin g and, ydien s u f f ic ie n t p ressu re i s ex e r te d , the
fu s io n o f th e wound parenchyma a r is in g from each.

I f e it h e r th e

sto ck or th e c io n does not form wound parenchyma ( c a l l u s ) , regard­
l e s s o f the amount formed by th e o th e r , no union can tak e p la c e .
S in ce th e c io n i s u s u a lly severed from i t s w ater supply some time
b efo re i t i s p la ced on the sto ck , i t s u f f e r s more from th e l o s s
o f w ater than th e sto ck does.
The walnut o ccu p ies a p o s it io n in term ed ia te between the
apple and the peach w ith resp ect to v e g e ta tiv e p rop agation.

The

apple can be propagated w ith ease by budding and by g r a f tin g on
both young and o ld t r e e s .

The peach i s very d i f f i c u l t to g r a ft

s u c c e s s f u lly , but can be budded w ith ease on young t r e e s .

The

walnut can o c c a s io n a lly be g ra fted w ith a f a i r degree o f su c cess
and can u s u a lly be budded, with good c io n wood,

w ith reason ab le

31

su ccess.

Why such v a r ia b le resp on ses?

I t seems th a t th e r e a c tio n

o f th e se p la n ts in an attem pt to h e a l wounds o f f e r s some c lu e t o
th e s it u a t io n .
I f th e bark o f th e sp p le i s p e e le d o f f when growth i s
a c t i v e , th e c e l l s l e f t on th e wood m u ltip ly r a p id ly , under fa v o r ­
a b le c o n d itio n s , fo im in g wound parenchyma or c a llu s d ir e c t ly on
th e su rfa ce o f th e wound.

L ater a cambium la y e r i s regen erated

and xylem and phloem are d if f e r e n t ia t e d (F ig . 1 6 ),
h e a lin g i s u s u a lly c a lle d r e g e n e r a tio n .

T his typ e o f

I f th e in ju r y i s such

th a t th e young c e l l s on th e su rfa ce o f th e wound are d estroyed ,
r e g e n e r a tio n h e a lin g does not tak e p la c e , but an e n t ir e ly d i f f e r ­
en t kind o f h e a lin g does occu r.

The cambium la y e r bordering th e

wound produces a p r o fu sio n o f parenchymatous c e l l s , which tend to
push over the wound.

F in a lly , a la y e r assumes t y p ic a l cambium

c h a r a c t e r is t ic s and produces xylem elem en ts on the in n er sid e and
phloem elem en ts on th e o u ter s id e .
wound by a l a t e r a l growth.

The cambium ten d s to cover th e

Such h e a lin g i s c a lle d w a llin g -o v e r

and i s i l l u s t r a t e d in F ig u res 9 , 10 and 1 2 .

I f th e o v e r -w a llin g

t i s s u e s from th e o p p o site s id e s o f th e wound meet w ith s u f f ic ie n t
p r e ssu r e , e it h e r b efo re th e cambium la y e r i s formed or a f t e r , th ey
u n it e , forming a con tin u ou s lajrer of t is s u e over the wound.
h as occurred in F ig u r e s 16 and 17.

T h is

Both ty p es o f h e a lin g occurred

in 16 and 1 7 .
The walnut has power t o h e a l by reg en era tio n under v ery
fa v o ra b le c o n d itio n s and a ls o to h e a l by o v e r -w a llin g , but t o a

32

l e s s e r degree than th e apple*

The peach forms reg en era tio n t is s u e

f r e e l y on young t r e e s but on o ld wood t h is type o f h e a lin g i s not
so common.
The p rod u ction o f wound gum, d i s t i n c t from th a t which
exudes from wounds on Prunus s p e c ie s , by which the v e s s e l s , t r a ­
c h e id s and ray c e l l s become plugged, seems to be an im portant
f a c t o r in th e su c c e ss or f a ilu r e o f g r a f tin g .

Swarbrick (54)

f in d s th a t such p lu g g in g occu rs t o th e ex ten t o f 0 .1 to 0 .3 mm.
fu r th e r than th e k n ife wound in rin ged apple stem s.

Bradford and

S itt o n (12) co n sid er gum form ation , e s p e c ia lly th e p lu g g in g o f
th e v e s s e l s , to be im portant in the h e a lin g o f wounds and in
g r a f tin g .

The w alnut a p p aren tly does not r e a c t to wounds in th e

same manner a s d oes the a p p le.

The walnut t i s s u e s im m ediately

below th e wound d ie fo r a co n sid era b le d ista n c e frcm the wound
b efo re gum form ation ta k es p la c e (F ig . 11, 1£, and 1 5 ).
5.

THE INFLUENCE OF GROSS ANATOMY.

In February, 1930, cio n s were secured from a s in g le
la r g e s e e d lin g tr e e on th e U nited S ta te s Pecan F ie ld S ta tio n ,
S h revep ort, L o u isia n a .

These were g ra fted on two year old seed ­

l i n g ro o t s to c k s , th e tap r o o ts o f which had been shortened to
about one f o o t .
As th e c io n s were b ein g prepared, about 240 were
measured a t th e p o in t where the b ev el was made on th e b a sa l end
o f th e c io n .

These measurements were (1) diam eter o f p it h , (2)

33

w id th o f xylem , i . e . , from p it h to cambium, (3) w idth o f bark,
i . e . , from th e cambium outward, and (4) t o t a l diam eter o f th e
stem .

The c io n s were tagged w ith s e r i a l numbers and th e meas­

urem ents record ed by number*

The age o f wood and th e t o t a l le n g th

o f the annual growth from which th e cio n was secured were a ls o
record ed .
The g r a f t s were prepared by the whip method, waxed and
packed in m o ist spaghnum in con stan t tem perature boxes, as d e sc r ib ­
ed l a t e r .

E ig h ty g r a f t s were exposed to each o f th e fo llo w in g

tem p eratu res, £ 4 °, 28° and 32° G.

The g r a f ts were allow ed to r e ­

main in th e boxes fo r fou r w eeks, at the end o f which time th ey
were removed and th e c a llu s form ation determ ined.

The g r a fts were

th en p la n te d in th e n u rsery row but u n fo r tu n a te ly , due to th e ex­
trem ely dry w eather which fo llo w e d , o n ly one g r a ft liv e d .

The

average c a l l u s form ation o f a l l g r a f t s was 6 8 .5 p er cent*
These d ata have been arranged on th e b a s is o f age of
c io n , le n g th o f annual growth from which th e e io n was secu red ,
diam eter o f th e p it h , diam eter o f th e c io n , r a t io o f the diam eter
o f th e p ith to th e diam eter o f th e c io n , width o f xylem , width o f
bark, width o f v a sc u la r t i s s u e .
TABLE 9 .
Age o f c io n
Per cen t c a llu s e d

INFLUENCE OF AGE OF CION ON CALLUS FORMATION.
1 year
54

2 year

3 year

79

80

4 year and over
75

Wood two or th r e e y ea rs o ld seems to p rovide b e t te r
c io n s than e it h e r younger or o ld er wood.

There i s v ery l i t t l e

34

d iff e r e n c e between two and th ree year o ld wood; in f a c t , th ere
i s much g r e a te r v a r ia t io n w ith in e it h e r age than i s h ere shown
betw een the two ages*
TABLE 1 0 .

INFLUENCE OF LENGTH OF ANNUAL GROWTH ON CALLUS FORMATION.

Length o f annual growth ( cm .)
P er c e n t c a llu s e d

10
74

15

20

25

30

35

40

45

65

70

54

50

40

100

82

The d ata fo r le n g th s o f 35 cm. and over rep resen t r e s u lt s
o f a sm all number o f g r a f t s , th e r e fo r e , should n ot be g iv en too
much w eight in a n a ly zin g th e r e s u l t s .

The le n g th o f th e annual

growth, per s e , probably i s not r e sp o n sib le fo r su c c e ss or f a ilu r e
in g r a f tin g , but g e n e r a lly th e lo n g er growth i s a s s o c ia te d w ith a
g r e a te r development o f th e shoot in a l l c h a r a c t e r is t ic s , p a r tic u la r ­
ly

in in c r e a s e in d iam eter.

Data in Table 11 seems to in d ic a te

th a t in c r e a s e in diam eter i s a s s o c ia te d w ith b e tte r c a llu s form ation.
TABLE 1 1 .

INFLUENCE OF TOTAL DIAMETER OF CION ON CALLUS FORMATION.

Diam eter o f stem (mm.)

6

Per cen t c a llu s e d

0

Q

10

5 3 .0 6 5 .0

12

14

8 2 .5 8 2 .5

These d ata in d ic a te th a t any stem h avin g a diam eter un­
der 10 mm., or 3 /8 in c h , i s u n su ita b le fo r c io n wood.

The average

le a d p e n c il i s about 8 mm., or 5 /1 6 in ch , in diam eter, so th a t th e
stat< 3nent o fte n made th a t wood th e s iz e o f a le a d p e n c il, or 1 /4
in ch in d iam eter, i s s u ita b le fo r c io n wood i s not s t r i c t l y co r­
r e c t in th e b lack w alnut.

I t would be nearer the tru th to say th a t

c io n wood should be 3 /0 to 5 /8 inch in diameter*

The data do not

35

show th a t wood la r g e r than 5 /8 in ch i s u n s a t is f a c t o r y from the
sta n d p o in t o f c a llu s form ation , but wood above th a t s iz e i s v e r y
d i f f i c u l t t o work w ith and, in a c tu a l p r a c t ic e , p referen ce should
be g iven to wood 3 /8 to 1 /2

inch in d iam eter.

A good ty p e o f c io n wood i s shown in the group to
r ig h t in F igu re 1 8 .

th e

T h is i s two year o ld wood o f a diam eter be­

tween 3 /8 and 5 /8 in c h .

The la rg e primary buds have a b sc ise d and

th o se rem aining are sm all secondary buds which w i l l push in to
growth r e a d ily when fo r c e d .

Next to th e l e f t i s a group o f one

year o ld s h o o ts .

p o r tio n o f th e s e sh oots i s s u it a b le

The b a sa l

f o r c io n wood but not q u ite

as good a s th e two year wood.

On th e

extreme l e f t i s a group o f sm all one year sh o o ts and next to i t
i s a group o f sm all two year sh o o ts.

Both o f th ese groups are

u n s u ita b le f o r c io n wood.

TABLE 1 2 .

INFLUENCE OF DIAMETER OF PITH ON CALLUS FORMATION.

Diam eter o f p ith (mm.)
P er cen t c a llu s e d

2
6 8 .5

2—2 .4

2 .4 —2 .8

6 7 .2

76 .6

2 .8 —3 .2

3 .2 —3 .6

3 .6 —4 .0

7 1 .0

78*0

6 5 .7

From t h e s e data, i t appears th a t th ere i s very l i t t l e ,
i f any, r e la t io n between th e s iz e o f th e p ith in a walnut stem and
th e c a llu s form ation .

The op in ion has o ften been exp ressed th a t

such a r e la t io n does e x i s t ; th a t c a llu s form ation and su c c e ss in
g r a ftin g was in in v e r se r a t io to th e s iz e o f th e p it h .

36

TABLE 1 3 .

INFLUENCE OF RATIO TOTAL DIAMETER OF STEM TO DIAMETER
OF PITH ON CALLUS FORMATION.

R a tio stem / p ith

2

2 .5

3

3 .5

4

4 .5

5

P er cen t c a llu s e d

0

75

68

82

91

92

64

These data are somewhat ir r e g u la r , but the p er cent
o f c a llu s form ation in c r e a s e s w ith in crea sed r a t io o f t o t a l diam­
e t e r o f th e stem t o p it h .

The data rep resen t r e s u lt s from c io n s

one, tw o, th r e e and fo u r y ea rs old*

I t i s probable th a t th e s iz e

o f th e p it h does n ot change m a te r ia lly a f t e r th e f i r s t la y e r o f
secondary xylem has m atured, c e r t a in ly no change occurs a f t e r th e
f i r s t y e a r ’ s growth i s com plete.

Data o f Table 11 show c le a r ly

th a t th e per ce n t c a llu s form ation in c r e a s e s w ith in creased
diam eter o f the stem .

Increased t o t a l diam eter i s accompanied by

approxim ately unchanged p it h diam eter, th e r e fo r e , i t must n e c e s­
s a r i l y fo llo w th a t th e in c r e a se in r a t i o , up to a c e r ta in p o in t,
would be a s s o c ia te d w ith in crea sed per cen t o f c a llu s form ation.
The d ata in d ic a te th a t th e maximum i s reached w ith a r a t io of 4 .5
b u t, s in c e sh o o ts w ith t o t a l diam eter g rea ter than 14 mm. were not
u se d , and d ata were n ot secured on r a t io s above 5, i t i s u n certa in
whether th e d ecrea se w ith the r a t io o f 5 i s a c tu a l or m erely a c c i­
d e n ta l.

O b servation s, w ith out a ctu a l measurements, in d ic a te th a t

c io n s la r g e r than 20 mm. in diam eter form c a llu s more slo w ly than
th e somewhat sm a ller o n es.

37

TABLE 1 4 .

INFLUENCE OF WIDTH OF XYLEM ON CALLUS FORMATION.

Width, o f xylem (mm.)
Per cen t c a llu s e d

1.6

2 .0

2 .4

2 .8

3 .2

3 .6

55

60

65

55

74

77

With th e e x c ep tio n o f th e xylem width o f 2 .8 mm.,
th e p er cen t o f c a llu s form ation in c r e a s e s w ith in crea sed width
o f xylem .

TABLE 1 5 .

INFLUENCE OF WIDTH OF BARK ON CALLUS FORMATION.

Y/idth o f bark (mm.)
P er cen t c a llu s e d

0 .6

0 .8

1 .0

1 .2

50

5 7 .5

6 9 .5

7 8 .5

1 .4 /
8 1 .5

Here th e per cen t o f c a llu s form ation in c r e a s e s w ith
th e th ic k n e s s o f the bark.
E a rly in th e p ro g ress o f the work, i t was observed
th a t c io n s w ith th ic k bark gave b e tte r r e s u lt s than c io n s having
t h in bark.

I t was a t f i r s t thought th a t th e amount o f cork f o r ­

m ation was la r g e ly r e sp o n sib le f o r t h is d iff e r e n c e , b ein g e f f e c t i v e
through

r e s is t a n c e to d e s ic c a tio n .
L ater experim ents in d ic a te th a t th e th ic k n e ss o f th e

bark i s not s o le l y r e s p o n s ib le , f o r stems having th ick bark a lso
have w e ll developed xylem and the in flu e n c e o f both xylem and
phloem c o n tr ib u te in th e same d ir e c t io n and t h e ir in flu e n c e cannot
be s e p a r a te ly e v a lu a te d .

C onsidering th e se f a c t s , i t seems probable

38

th a t th e b e n e f it s o f the th ic k e r v a sc u la r t is s u e must be a t l e a s t
two f o ld ; f i r s t , the cork f o m a t io n i s more e f f i c i e n t in con­
se r v in g m o istu re and second, the th ic k e r v a sc u la r t is s u e g iv e s g r ea ter
sto r a g e o f r e se r v e fo o d s upon which to draw fo r th e form ation o f
wound parenchyma and new t i s s u e .

TABLE 1 6 .

INFLUENCE OF WIDTH OF VASCULAR TISSUE ON CALLUS
FORMATION.

Width (mm.)

2 .0

Per cen t c a llu s e d

33

2 .4
47

2 .8

3 .2

3 .6

4 .0

4 .4

4 .8

64

61

62

68

76

77

5 .2

5 .6

90 100

With the e x c ep tio n o f th e w idth o f 2 .8 ram., th ere i s
an in c r e a s e in th e p ercen tage o f c a llu s e d g r a f t s w ith in c r e a s in g
w idth o f v a sc u la r t i s s u e .

T h is seems to s ig n i f y th a t c a llu s f o r ­

m ation ta k e s p la c e more r a p id ly where th e v a scu la r t is s u e i s w e ll
d ev elo p ed , presumably meaning th a t th ere i s more storage space
f o r r e se r v e fo o d s and th a t a b e t te r system fo r t h e ir tr a n s lo c a tio n
i s p rovid ed .
W inkler (59) r e p o r ts th a t grape c u ttin g s w ith high
sta rc h co n ten t produced a h igh er percen tage o f r o o tin g than c u t­
t in g s w ith medium and low c o n ten t.

He does not show com parative

measurements o f d iam eter, but h is f ig u r e s
c la s s e d as having h igh

show th at the stems

sta rch content had co n sid era b ly g rea ter

e t e r than th e stems o f medium and low starch c o n te n t.

diam­

39

5.

INFLUENCE OF RELATIVE ATMOSPHERIC HUMIDITY.
Apparatus*

S ix boxes were c o n stru cted , each h avin g dim ensions
o f 16 x 20 x 12 inches*

These were made o f 12 inch lumber w ith

one 16 x 20 s id e l e f t open and th e o th er covered by g la ss*
box was p rovided w ith a h e a tin g c o i l and a thermometer*

Each

S ix o f

th e s e boxes were co n stru cted and th e h e a tin g elem ent so ad ju sted
and w ired in s e r i e s th a t a l l were c o n tr o lle d by one theremoregula to r *

The t o t a l r e s is t a n c e was such th at the h e a tin g elem ents

would glow o n ly f a i n t l y when th e f u l l current was on.

T his pro­

v i s i o n was made to avoid b lis t e r i n g th e c io n s near th e h e a te r .
The th erm oregu lator was a d ju sted so th a t the temperature w ith in
th e b oxes was 28° to 30° C*

Cions were g r a fte d on shortened ro o t

s to c k s which were p la n te d in m oist

p eat in a greenhouse bed. The

g r a f t s were allow ed t o p r o je c t through double th ic k n e s s e s o f ta r
paper which was spread over th e top o f th e p e a t.
through which the g r a f t s p ro je c te d were

The h o le s

se a le d w ith g r a ftin g wax.

The box was then p la ce d over the g r a f t s , g la s s s id e up.
R e la tiv e Humidity.
The r e l a t i v e hu m idity of th e a ir was c o n tr o lle d a t
(l)

alm ost dry, (2) 25$, {3). 50$, (4) 65$, (5) 75$, and (6)

s a tu r a te d .
A ccording to W ilson (58) a su lp h u ric a cid s o lu t io n o f
a g iven p ercen ta g e com position has a con stan t vapor p ressu re and,

40

when exposed in a c o n fin ed sp a c e , m ain tain s th e atm ospheric hum idity
a t a c o n sta n t degree fo r a con stan t temperature*

T h erefore, th e

su lp h u r ic a cid s o lu t io n s were u t i l i z e d t o m ain tain the atm ospheric
h u m id itie s .
E vap oratin g d is h e s were p laced under each box and kept
f i l l e d as fo llo w s :
(1)

Dry atmosphere

(2)

25% r e l a t i v e huzuidity-§5.9% su lp h u ric a c id , changed f r e ­

ts )

50%

"

4 3 ,4

,f

ft

(4)

65%

"

3 6 .0

M

,f

(5)

75%

«

4,o

"

,f

(6)

S atu rated

"

Calcium c h lo r id e , changed fr e q u e n tly

tf

d i s t i l l e d w ater

I t i s reco g n ized t h a t, under th e c o n d itio n s o f t h is
exp erim en t, i t i s im p o ssib le to m aintain the atm ospheric humid­
i t i e s a c c u r a te ly b ecau se th e p o r tio n o f th e stem exposed i s con­
s t a n t ly g iv in g o f f m o istu re, and because m oisture was not com­
p l e t e l y exclu d ed by the ta r paper*

I t i s b e lie v e d th a t the atmos­

p h er ic h u m id itie s were m aintained n e a rly enough to th e d esir e d
amounts, e s p e c i a ll y in th e second s e r ie s o f experim ents*
Cion wood was secured from th e tr e e s in th e nursery o f
th e F o r e str y Department a s d escrib ed before*

This c o n s is te d o f

two year o ld wood as n e a r ly as p o s s ib le of diam eters between 5 /8
and 1 /2 inch*

They were g r a fte d , t ie d and waxed as u su a l and

p la n te d in th e p eat and th e box p la ced over them*

The f i r s t s e r ie s

41

rem ained in th e b oxes th r ee weeks and the second s e r i e s two weeks.
Twenty w alnut and te n apple g r a f ts were used in th e f i r s t s e r ie s
and 25 walnut and 8 apple g r a f ts in th e second.
Table 17 g iv e s th e r e s u lt s o f th e s e experim ents.

TABLE 1 7 .

INFLUENCE OF ATMOSPHERIC HUMIDITY ON CALLUS FORMATION
AT TEMPERATURE OF 28° C.

R e la t iv e h u m idity (p er ce n t)

0

25

50

65

75

S a t.

F ir s t s e r ie s :
Per c en t

c a llu s e d , walnut

35

30

50

45

70

90

Per c en t

c a llu s e d , apple

60

50

10

10

50

60

Per c e n t

c a llu s e d , w alnut

12

52

60

-

72

95

Per ce n t

c a llu s e d , apple

89

89

78

-

100

100

Second s e r ie s :

From th e s e r e s u l t s , i t appears th a t th e atm ospheric hum idity to
which th e walnut g r a f ts are exposed i s somewhat im portant.

Where

a r t i f i c i a l tem peratures are m aintained a t r e l a t i v e l y h igh d egree,
p r o v is io n should be made to keep the r e l a t i v e hum idity compara­
t i v e l y h ig h .
7.

INFLUENCE OF TEMPERATURE.

In 1928, c io n wood was kept in co ld sto ra g e a t about
5° C.

Although th e c io n wood remained in sto ra g e se v e r a l weeks,

none o f i t formed c a l l u s .

When the season ’ s g r a ftin g was com plete,

th e r e was a small amount o f cio n wood l e f t over.

About t h is tim e

42

th e c o o lin g p la n t was shut down so th a t the tem perature o f th e
sto ra g e ro se to 20-22° 0 .

About ten days l a t e r , when preparin g

to d isp o s e o f th e c io n wood, n e a r ly every p ie c e o f cio n wood had
formed c a l l u s , seme q u ite p rofu sely*
C erta in g r a f ts were made l a t e r than o th e r s t h is year,
when th e tem perature was somewhat higher*

These la t e r s e t g r a f ts

did somewhat b e t t e r than th o se s e t e a r l i e r .

These o b se rv a tio n s

le d t o an e la b o r a tio n o f th e problem t o in clu d e th e in flu e n c e o f
tem perature upon g ra ftin g *
Apparatus.
To study the in flu e n c e o f tem perature, i t was n eces­
sary to c o n str u c t a s e r i e s o f boxes by means o f which th e g r a fts
co u ld be exposed t o c o n tr o lle d tem peratures*

I t i s o fte n sa id

th a t th e c io n b eg in s growing b efore c a llu s form ation and union
can tak e p la c e , thus d e p le tin g the supply of reserv e food to a
p o in t such th a t union cannot be formed*

To avoid t h i s , boxes

were c o n str u c te d in which a space 24 x 24 x 3 in ch es was h ea ted .
G rafts were made and in s e r te d through h o le s in th e 24 x 24 inch
s id e s so th a t the top protruded from one s id e end the root from
th e o th er w ith th e union w ith in th e heated sp a ce.

T his arrange­

ment p rovid ed f o r th e h ea tin g o f about an inch and a h a lf o f the
top p o r tio n o f th e sto c k and a sim ila r amount o f th e b a sa l por­
t io n o f th e c io n .
The union o f th e g r a ft was waxed b efore in s e r t io n in

43

th e box and th e h o le s through which th e c io n and stock p r o je c te d
were plugged w ith co rk s and waxed.

M oist p eat was packed around

th e ro o ts#
An ord in ary 5 0-w a tt lamp bulb was used as a source o f
h ea t f o r t h e f i r s t s e r i e s but was found u n s a t is f a c t o r y .

There­

a f t e r , a r e s is t a n c e c o i l o f nichrome w ire was u sed , b ein g so ad­
ju ste d th a t when f u l l cu rren t was on the w ire was ju st below th e
p o in t o f glow h e a t.

In com plete darkness, a f a in t red glow was

produced but no glow was n o tic e a b le in d iff u s e d l i $ i t .

In t h is

manner, th e in ju r io u s e f f e c t s o f in te n s e rad ian t h eat were
avoided.
Temperature was c o n tr o lle d w ith a de K hotinsky thermor e g u la to r w ired in s e r i e s w ith th e h ea tin g e l ament so th a t a r i s e
in tem perature above the p o in t a t which th e r e g u la to r was s e t
caused th e p latinum p o in ts o f the r e g u la to r to sep arate and break
th e current p a ssin g through the h e a te r .

The p o in ts then remained

open u n t i l th e tem perature o f th e box dropped below the d e sire d
p o in t.
A fte r two s e r i e s o f experim ents were conducted, th e se
boxes were discarded* and b oxes s im ila r to th o se d escrib ed fo r
th e atm ospheric hum idity s tu d ie s were used f o r se v e r a l s e r i e s ,
when th ey were d isca rd ed in favor o f th e f i n a l form.
The f in a l form of th e con stan t tem perature box was one
18 x 24 x 24 in c h e s, in which the e n t ir e sto ck and cio n was p la ced

44

(F ig . 1 9 ) , th e r o o ts b ein g packed in m oist spaghnum or p eat
moss in a w ire b ask et in s id e th e box.
The box i s h ea ted by e l e c t r i c i t y , u sin g a 110 v o lt
c u r r e n t.

The h e a tin g elem ent i s a c o n ic a l p o r c e la in core wound

w ith nichrome r e s is t a n c e w ire, such a s are used in p o rta b le
r a d ia n t e l e c t r i c h e a t e r s .

T his ela n en t i s wired in s e r ie s w ith

a th erm oregu lator.
A w ire b ask et i s p la ced in th e box, supported f r e e from
th e f lo o r so a s t o le a v e a two inch space f o r a ir c ir c u la t io n .
An a ir space i s p rovided above and on two s id e s o f th e b a sk e t,
w h ile th e o th er two s id e s are p laced c lo s e a g a in st th e s id e w a ll
o f th e box;

T h is arrangement p ro v id es fo r c ir c u la t io n o f a ir by

c o n v e c tio n , r i s i n g from th e h e a te r , p a ssin g over th e b ask et and
down on th e o p p o site s id e , under th e b ask et and back t o th e heater*
The bask et i s provided w ith a s o lid sh e et iro n sid e
n ex t to the h e a te r to p r o te c t th e g r a f ts from d ir e c t ra d ia n t h e a t.
The w a lls o f th e box are made double, the o u ter one
b ein g o f matched inch lumber and th e in n er o f 3 /8 inch w a ll p la s ­
t e r board; th e space between the two w a lls i s f i l l e d w ith an in ­
s u la t in g m a te r ia l.
Cion Wood.
Cion wood fo r th e f i r s t th ree s e r ie s was ob tain ed from
th e same t r e e s in th e n u rsery o f th e F o r estry Department as de­
sc r ib e d e a r l i e r .

Cion wood fo r the fo u rth s e r ie s was ob tain ed

45

from th e orchard o f Mr* Henry M# W allace, H ighland, Michigan*
These t r e e s had been n e g le c te d up to two y ea rs p reviou s to the
tim e when th e c io n wood was cut*

The t r e e s had made good growth

f o r th e p a st two sea so n s and some good wood was o b tain ed .
For th e f i f t h s e r i e s , c io n wood was ob tain ed from a
s in g le la r g e s e e d lin g t r e e on th e Pecan F ie ld S ta tio n o f the
U nited S t a te s Department o f A g r ic u ltu r e , Shreveport, L ou isian a.
Root S tock .
For the f i r s t th r e e s e r i e s , th e root sto ck was ob­
ta in e d from th e b lock o f s e e d lin g s u sed as ro o t sto ck s in th e
p r ev io u s f i e l d work.

For th e oth er s e r i e s , v igorou s two year

o ld s e e d lin g s , most o f which were about 3 /8 in ch in diam eter
a t th e ground l i n e , were used*

S eed lin g s were dug and the tap

ro o t shortened to 8 to 12 in c h e s.

The top was cut back and

th e g r a ft was u s u a lly p laced ju st above th e ju n c tio n of th e ro o t
and stem.
Procedure.
G rafts were made by the u su a l whip g r a ft method,
waxed and exposed to th e c o n tr o lle d tem peratures as soon as
p o s s ib le .

G rafts were made fo r th e f i r s t s e r ie s January 10

to 21, and fo r th e second s e r i e s , March 11 and 12, and fo r the
th ir d s e r i e s , A p r il 28, 1929.

S ix te e n , 20 and 25 g r a f ts , r e ­

s p e c t iv e ly , were used fo r each tem perature.
S in ce o n ly f i v e constant temperature boxes were

46

a v a ila b le , th e tem peratures to which th e g r a f t s were exposed
were v a r ie d w ith each s e r ie s #

These tem peratu res, w ith th e per

cen t o f g r a f t s forming c a l l u s , are g iv en in Table 18#

TABLE 1 8 .

INFLUENCE OF TEMPERATURE ON CALLUS FORMATION IN
WALNUT GRAFTING. FIRST THREE SERIES COMBINED.

Temperature ° C.

5

15 20

S e r ie s 1
Per c en t c a llu s e d 0
S e r ie s 2
Per cen t c a llu s e d

24

0
15 30

S e r ie s 3
P er cen t c a llu s e d

32

25 26

28

30 32

44

31

40

40
50

54

40

35 40
0

0

25
20

A fte r th e g r a f t s were removed from th e tem perature b oxes, th o se
showing c a llu s were p la n ted in a greenhouse bench in sand and
allow ed to grow.

The per cen t o f g r a f ts which grew c o r r e la te d

v e r y c l o s e l y w ith th e per cen t th a t c a llu s e d , in d ic a tin g th a t
union u s u a lly i s accom plished on g r a f t s which form c a llu s .
The d a ta show th e in flu e n c e o f tem perature on c a llu s
fo n a a tio n q u ite c le a r ly .

There was l i t t l e or no c a llu s fonned

below 20® C. in most c a s e s , and th a t formed at 20° was v ery weak.
At 25° to 30® C ., c a llu s formed more r e a d ily , e s p e c ia lly a t 26°
and 28®C.

Above 30° C th e c a llu s form ation was weak and none

occurred a t 40® C.
In g en er a l where c a llu s form ation took p la c e , i t was

47

more abundant on th o se g r a f ts exposed to tem peratures o f 25°
t o 30° C.

When th e g r a f t s were allow ed t o grow, th e growth

was more v ig o r o u s and th e f o li a g e a darker green , on g r a f ts
exposed a t th e se tem peratures (Fig* 20)*
At 32° C. and above, many o f th e c io n s were in ju red
ap p a ren tly from d yin g o f e x c e s s iv e h e a t.

T h is seems to be tru e

e s p e c i a ll y o f c io n s having com p aratively th in bark w ith l i t t l e
cork form ation*
Two a d d itio n a l experim ents on th e in flu e n c e o f tem­
p eratu re were conducted.

In the f i r s t o f t h e s e , in a d d itio n to

tem perature, th e e f f e c t o f waxing th e e n t ir e c io n upon the r e ­
s u l t s a ls o r e c e iv e d a t t e n t io n .

In th e second, th e in flu e n c e o f

v a r io u s f a c t o r s o f g ro ss anatomy were co n sid ered .
G ra fts were made May 1 2 , 13 and 1 4 , 1929, and p la ced
in boxes w ith tem peratures m aintained a t 2 0 ° , 23°, 26°, 29° and
32° C ., r e s p e c tiv e ly *

In each box were p la ced 23 g r a f ts w ith

c io n s o f th e Ohio v a r ie t y , waxed in th e u su a l way, 6 g r a f ts o f
Ohio h avin g e n t ir e c io n and union waxed w ith p a r a ffin , 7 g r a f ts
w ith c io n s o f Ten Eyck waxed in th e u su a l way and 4 Ten Eyck
having e n t ir e c io n waxed.
These g r a f ts were allow ed to remain in th e boxes 14
days and were th en removed and p la n ted in th e n u rsery.

On

August 9 , th ey were examined and th e number growing recorded;
r e s u l t s are p resen ted in Table 19.

48

TABLE 1 9 .

INFLUENCE OP TEMPERATURE ON THE UNION IN WALNUT
GRAFTING. FOURTH SERIES.

Temperature ° C.

20

23

26

29

32

Per c e n t growing, a l l g r a f ts

16

31

45

26

35

P er c e n t growing, re g u la r waxing

14

26

32

32

32

27

Per cen t growing, waxed e n tir e

20

44

78

16

44

42

T o ta ls

These r e s u lt s agree in gen eral w ith th o se o f the p re­
ced in g exp erim en ts in th a t th e tem peratures 26° to 30° 0 . again
g iv e b e s t r e s u l t s .

In t h is s e r i e s , th e c io n wood was not so u n i­

form a s th e p reced in g o n es, and having such v a r ia t io n s com p licates
th e e f f e c t o f th e tem peratures.
M orris ( 3 6 ), N ie lso n ( 4 0 ), and o th e r s have advocated
s tr o n g ly th e c o a tin g o f th e e n tir e cio n w ith p a r a f fin , or p arap in,
but have n o t g iv e n data on com parative t e s t s .

The r e s u lt s o f th e

waxing trea tm en ts in t h i s s e r i e s in d ic a te th a t some advantage i s
d eriv ed from such treatm ent but th e d iffe r e n c e s are not v ery s i g ­
n ific a n t.

F urther in v e s t ig a t io n s o f waxing th e e n tir e cio n are

needed.
A v ery s e r io u s o b je c tio n to the u se o f p a r a ffin a lo n e,
o r mixed w ith some o th er substance to r a is e the m e ltin g p o in t,
was observed in th e s e t r i a l s .

When t h is m a teria l i s m elted , i t

becomes very th in and h as low v i s c o s i t y , making i t d i f f i c u l t to
secu re a good s e a l around th e u n ion .
Cion wood fo r the l a s t tem perature experim ent was ob-

49

ta in e d from a s in g le , la r g e s e e d lin g t r e e lo c a te d on th e Pecan
F ie ld S ta tio n o f th e U n ited S ta te s Department o f A g r ic u ltu r e ,
S h revep ort, L ouisiana*
In t h i s s e r i e s , cio n wood o f one, two and th r e e year
o ld wood was used*

There was much v a r ia tio n in th e s iz e o f th e

wood; t h i s v a r ia t io n was used to o b ta in d ata on th e in flu e n c e o f
g ro ss anatomy a s p r e v io u s ly d iscu ssed *

A t o t a l o f 120 g r a f t s was

p la ce d in each o f the fo llo w in g tem peratures: 2 0 °, 2 4 °, 2 8 °, 32°
and 36° C*

The f i n a l form o f con stan t terpperature boxes was used

f o r t h i s s e r i e s o f experim ents*

The

g r a f t s remained in th e boxes

fo u r weeks and then were removed

and

examined fo r c a llu s form ation*

R e s u lts a re p resen ted in Table 20*

TABLE 20.

INFLUENCE OF TEMPERATURE ON CALLUS FORMATION.
SERIES*

Temperature, ° C*

20

Per ce n t c a llu s form ation

13*5

24

28

32

36

7 2 .8

8 6 .4

31*4

24 .3

FIFTH

Again the data in d ic a te th a t tem peratures o f 24° to
30° C. are most fa v o ra b le fo r c a llu s form ation in th e w alnut, w ith
th e optimum a t or near 28° C*

The degree o f c a llu s form ation at

28° C. i s h igh enough to be con sid ered com m ercially s a tis fa c to r y *
These data seem e s p e c ia lly s ig n if ic a n t because o f th e
wide v a r ia t io n in the c io n wood u sed in th e s e exp erim ents.

Much

o f i t cou ld n ot be con sid ered s u it a b le , and some was v e r y sm all

50

on© year •wood which h as c o n s is t e n t ly g iv en poor r e s u lts #
DISCUSSION
I t i s q u ite c le a r from th ese experim ents t h a t , by ex­
posure o f th e g r a f t s t o th e optimum tem perature, which ap p aren tly
l i e s in th e neighborhood o f £8° C#, i t i s p o s s ib le to in c r e a se th e
r a te a t which wound parenchyma i s produced#

In t h i s manner i t i s

p o s s ib le to in c r e a s e th e percen tage o f g r a f t s form ing c a llu s and
th u s in c r e a s e the per cen t o f s u c c e s s fu l unions#

I t must be

r e a liz e d th a t union does n ot always f o llo w c a llu s f o m a t io n , but
union cannot be accom plished u n le s s c a llu s or wound parenchyma i s
produced.
That oth er f a c t o r s b e s id e s tem perature are o p era tiv e i s
in d ic a te d by th e s tu d ie s in anatomy, g ro ss anatomy and chem ical r e ­
la tio n s #

However, i f the temperature v a r ie s much from the optimum,

th e c a llu s form ation , even in the b e s t ty p e s o f c io n wood, i s v ery
u n sa tisfa c to r y #

I t would, th e r e fo r e , appear t h a t, o f a l l th e fa c ­

t o r s in v e s t ig a te d a f f e c t in g g r a ftin g in th e black w alnut, tempera­
tu re i s o f primary importance#
I t i s probable th a t tem perature a c t s in d ir e c t ly through
in cr e a se d chem ical a c t i v i t y , e s p e c ia lly a s th e chem ical a c t i v i t y
i s c a ta ly z e d by enzymes#

I f th e d ata on th e in flu e n c e o f tempera­

tu re be p lo tt e d (Fig# 21) a curve i s obtained which c lo s e ly resem­
b le s th e typ e o f curve ob tain ed fo r th e r e la t io n between tempera-

51

tu r e and enzyme a c t i v i t y (1 8 , 19 and 32)*

The optimum and a l l

p o in ts on t h i s curve occur a t low er tem peratures than fo r the
t y p ic a l curve a s rep resen ted by th e h y d r o ly sis o f m altose by
m a lta se ( 1 9 ).

In th e l a t t e r ca se th e optimum v a r ie s w ith th e

hydrogen io n c o n e c n tr a tio n o f th e medium from 35° C. to 47° C.
J u st why growth in th e walnut stem responds t o low er tem perature
and i s p r o h ib ite d a t tem peratures optimum fo r enzyme a c t i v i t y , as
fr e q u e n tly r e p o rte d , i s not e n t ir e l y c le a r , but the tim e f a c to r
probably i s o f g rea t importance*
In any b io lo g ic a l system time i s a f a c to r equal in
im portance to any oth er v a ria b le*

Most o f th e s tu d ie s on enzy­

m atic a c t i v i t y have been conducted fo r r e l a t i v e l y short p e r io d s,
measured in hours*

Very fr e q u e n tly statem en ts are made th a t 37° 0*

i s th e optimum fo r enzym atic a c t i v i t y , which i s probably tru e fo r
enzymes o b ta in ed from warm-blooded an im als, i f th e tim e o f th e
r e a c tio n i s short*

With enzymes d erived from p la n ts and w ith th e

r e a c tio n p ro ceed in g over a lo n g er p eriod o f tim e th e optimum tem­
p eratu re w i l l approach room temperature*

Every enzym atic r e a c tio n

ta k in g p la c e c o n s is t s o f a t l e a s t two p h a ses, enzyme a c tio n and
enzyme d e s tr u c tio n , and th e r a te o f in crea se o f enzyme a c t i v i t y and
th e r a te o f in c r e a s e o f enzyme d e s tr u c tio n probably bear no con­
s ta n t r e la t io n s h ip .

Eor sh ort p erio d s of tim e, h igh er tem peratures

would produce g r e a te r enzyme a c t i v i t y but t h is m ight be accompanied
by g r e a te r enzyme in a c t iv a t io n .

With s t i l l h igh er tem peratures the

52

th e in a c t iv a t io n may he p r o g r e ssin g at a much g r e a te r speed
than th e a c t iv a t io n , so th a t the enzyme may he in a c tiv a te d be­
fo r e th ere aie any a p p recia b le p rod u cts o f th e rea ctio n *

It is

e n t i r e l y p o s s i b l e , and v e r y p rob ab le, th a t had th e r e a c tio n been
. co n tin u ed f o r a lo n g e r tim e th e t o t a l prod ucts would have been
g r e a te r a t a low er tem perature than th a t which appeared to be th e
optimum e a r ly in th e p r o g r e ss o f the rea ctio n *
In p la n t t i s s u e th e resp on se to ton p eratu re i s much
slow er than th a t o f enzymes from warm-blooded anim als in a r t i f i ­
c i a l media*

In th e experim ents h e r e in rep o rted , th e tim e was

lo n g and the r e s u l t s ap p aren tly show th e in flu e n c e o f enzyme
a c t i v i t y a t tem peratures between 25° and 50° C. and anzyme in a c ­
t iv a t i o n a t tem peratures above 30° C*
Among th e f a c to r s which may be a s s o c ia te d w ith th e de­
p r e s sio n o f growth a t th e h igh er tem peratures i s th e d e f ic ie n c y
o f m oistu re w ith in th e stem a v a ila b le fo r chem ical a c t io n .

At

th e h ig h er tem perature the m oistu re may be evaporated or o th er­
w ise removed*

The h ig h er tem peratures may cause a c e r ta in amount

o f c o a g u la tio n o f the c o l lo id a l m a te r ia l w ith in th e c e l l and thus
reta rd growth*
The curve f o r c a llu s form ation agrees w ith growth
cu rv es in g en era l ex cep t th a t th e r i s e in the curve i s more abrupt
than th e u su a l growth curve b u t, had more d eterm in ation s been made,
i t i s p o s s ib le th a t a smoother curve would have been obtained*

In

53

c e r ta in o f th e ex p erim en ts, apple g r a f ts were exposed to th e same
tem p eratu res as the w alnut g r a f t s .

These produced more c a llu s a t

b oth low er and h ig h er tem peratures than d id walnut g r a f ts and, i f
th esB data were p lo t t e d , a f l a t t e r curve would be o b ta in ed .

It is

ev id en t th a t p art o f th e resp o n se o f th e w alnut to tem perature i s
g en era l and p a rt s p e c if i c fo r th e s p e c ie .
Although the w r ite r has been unable to secure any
m a te r ia l and c o n s is te n t improvement in g r a ftin g o f th e b lack w al­
nut through g ir d lin g or d e f o lia t in g th e sh o o ts or through n itr o g e ­
nous f e r t i l i z e r s , i t i s q u ite ev id en t th a t th e co n d itio n of the
sh o o ts used f o r c io n s and a ls o th e c o n d itio n o f s e e d lin g s used fo r
sto ck i s im portant.

Evidence of t h is i s had in th e data p resen ted

upon the in flu e n c e o f th e g ro ss anatomy o f th e c io n .

R eference

re p e a te d ly o ccu rs in l i t e r a t u r e r e la t in g to propagation by budding
and g r a f tin g , both in r e sp e c t to th e walnut and t o oth er f r u i t s ,
to th e e f f e c t th a t w e ll matured sh o o ts g iv e more s a t is f a c t o r y r e ­
s u l t s than p o o r ly matured s h o o ts.

The term " w ell matured" e v id e n t­

l y means w e ll n ou rish ed , th a t i s , sh o o ts which grew

m oderately

v ig o r o u sly and had s u f f i c ie n t f o li a g s p rop erly exposed t o su n lig h t
to supply abundant m a te r ia ls , both carbohydrate and p r o te in , fo r
sto r a g e .

One p r e r e q u is ite fo r vig o ro u s growth i s a supply o f s o i l

n u tr ie n t s , e s p e c i a ll y n itr o g e n .
D ir e c t ev id en ce was not secured in t h i s regard, but th e
c o n s is t e n t ly poor r e s u l t s w ith d e f o lia t e d sh o o ts in d ic a te th a t

54

sto r e d n u t r ie n t s are im portant.

The sh o o ts used in the l a s t

s e r i e s o f experim ents were secured from a tow o f t r e e s borderin g
a c u lt iv a t e d f i e l d .

These t r e e s were w e ll spaced so th a t they

r e c e iv e d abundant s u n lig h t .

G rafts made from th e se sh o o ts were

exposed t o th e tem perature which i s approxim ately optimum and r e ­
s u l t s o f from

76%> to 90% "take” were secu red .

In t h is c a s e , w ith

two and th re e year o ld wood, m a te r ia ls and c o n d itio n s a s n e a rly
id e a l a s p o s s ib le were secu red .
There are ap p aren tly two primary r e q u is it e s f o r suc­
c e s s f u l g r a f tin g o f th e b lack walnut; s u ita b le cio n wood and o p t i­
mum tem perature.

Probably o f o n ly s l i g h t l y l e s s im portance i s a

sto ck in th e proper c o n d itio n o f v ig o r .
S h oots which w i l l make s u ita b le c io n wood u s u a lly can
be o b tain ed frcm t r e e s 8 to 12 years o ld in a moderate s t a t e o f
v ig o r , r e t a in in g t h e ir f o lia g e in a h e a lth y c o n d itio n u n t i l normal
tim e fo r l e a f f a l l , and w e ll exposed to su n lig h t and c ir c u la t io n
o f air*
The most s a t is f a c t o r y method fo r secu rin g the proper
*
tem perature must be adapted by th e in d iv id u a l to s u it h i s p a r tic u ­
l a r n eed s.

A v e r y s a t is f a c t o r y chamber in which the tem perature

can be c o n tr o lle d and in which a la r g e number o f g r a f t s can be
c a llu s e d , can be co n stru cted a t a reasonable c o s t .

The c o s t o f

o p e r a tin g such a chamber would a ls o be rea so n a b le.

However, th e

walnut i s somewhat d i f f i c u l t to tra n sp la n t and i t has not been
determ ined how many o f th e c a llu s e d g r a f ts can be grown in to good

55

tr e e s*

B efo re t h i s method o f bench g r a f tin g and c a llu s in g in an

in c u b a to r can be recommended g e n e r a lly , fu r th e r experim ents are
needed t o determ ine th e b e st method o f h an d lin g th e g r a f t s subse­
quent to c a llu s in g , a ls o th e e f f e c t o f the tem perature on th e
ro o t and i t s subsequent b eh avior should r e c e iv e a t t e n t io n .
Where a r t i f i c i a l tem peratures cannot be u t i l i z e d , i t
i s su g g ested th a t th e g r a ftin g o p e r a tio n s be d elayed u n t i l th e
tem perature rem ains above 70° F. fo r a c o n sid era b le p o r tio n o f th e
day*

T h is w i l l p rohably mean th a t th e sto ck w i l l have s ta r te d in to

growth and th a t care must be e x e r c is e d to make th e g r a f ts w ithout
te a r in g th e bark away.

A fte r th e g r a ft i s made, some p r o v isio n

f o r m a in ta in in g th e tem perature m i^ it be made, such a s co v erin g
th e union and a t l e a s t a p o r tio n o f th e c io n and sto ck w ith a
b la ck paper.

The b lack paper would absorb h eat from th e su n lig h t

and the tem perature would be in c r e a se d .
P o s s ib ly g r a ftin g in autumn may prove advantageous.
The g r a ft m ight be s e t in the c o l l a r , below th e su rfa ce o f th e
ground and th e s o i l banked around the c io n , le a v in g one bud uncov­
ered .

I t i s p o s s ib le th a t th e s o i l would be warm enough to induce

u n itin g .

The proper tim e fo r t h i s would probably be during August

in M ichigan, or in September in the so u th .

These g r a fts would then

be a llow ed to p a ss through th e w in ter in p la ce and during th e f o l ­
low in g sp rin g would fo r c e in to growth, g iv in g a f a i r s iz e d t r e e by
f a l l , one year a f t e r g r a f tin g .
There i s u n c e r ta in ty as to whether th e g r a ft w i l l form

56

c a l l u s a t th a t tim e o f the year*

An in d ic a tio n th a t c a llu s w i l l

form in f a l l i s had on c io n s which were rin ged to prepare them
f o r th e sto re d n u tr ie n t stu d ies#

Some o f t h is was done in August

in M ichigan and some in September in Louisiana*

In both c a s e s ,

c a l l u s form ation took p la c e above th e wound.
A d d itio n a l work might w e ll be done w ith th e p atch bud
method o f propagation*

The p relim in ary work rep orted h ere and th e

s u c c e ss o f t h i s method w ith pecan prop agation in d ic a te th a t th e
method could be developed fo r the w alnu t.

The primary problem

seems to be to fin d what c o n s t it u t e s s u it a b le c io n wood

and t o f in d

a s a t i s f a c t o r y method o f s to r in g th e wood u n t i l needed*

S lig h t

m o d ific a tio n s in th e technique m i^ it w e ll be made in order t o speed
th e work*
On th e w hole, th ere i s probably more hope fo r th e com­
m e rc ia l p rop agation o f th e b lack walnut by budding than by g r a f t in g .
SUMMARY.
1#

The b la ck walnut i s v ery d i f f i c u l t to propagate

a s e x u a lly , as rep o rted by most authors d e a lin g w ith th e s u b je c t.
2.

A pparently, a p p lic a tio n s o f n itro g en o u s f e r t i l i z e r s

or g ir d lin g o f th e sh o o ts does n ot have s u f f i c ie n t in flu e n c e to
m a te r ia lly a l t e r th e b eh avior o f walnut c io n s upon g r a f t in g .

Par­

t i a l d e f o li a t i o n seems t o d epress the per cen t o f c a llu s form ation*
3*

Treatment o f th e c io n wood by ch em icals did not in ­

c r e a se th e p ercen tage o f

g r a f ts u n itin g .

57

4.

P rop agation by th e patch bud method o f f e r s prom ise

but th e r e are d e t a i l s o f t h i s method which s t i l l need a t t e n t io n .
5.

A natom ical s tu d ie s in d ic a t e th a t the walnut i s more

s e n s i t i v e to wounds than i s th e a p p le .

P r o te c tio n o f th e wood

from d e s ic c a tio n by p lu g g in g o f th e xylem t is s u e s p roceed s much
more s lo w ly in th e walnut than in the a p p le.

New t i s s u e in th e

walnut i s ca p a b le o f changing d ir e c t io n to meet changed c o n d itio n s
o f sap flo w .
6.

Study o f c io n wood from th e stan d p oin t o f g ro ss

anatomy in d ic a te s : (a) c io n wood two and th ree y ea rs o ld gave b e t­
t e r r e s u l t s than o ld e r or younger c io n s; in g e n e r a l, two year wood
i s p refe rr ed ; (b) c io n s h avin g a diam eter between 3 /8 and 5 /8 in ch ,
i n c lu s iv e , g iv e b e t t e r r e s u lt s than th o se e it h e r la r g e r or sm aller;
(c) the p ercen tage o f c io n s form ing c a l lu s i s independent o f th e
s iz e o f th e p ith ; (d) th e per cen t o f c io n s form ing c a llu s in c r e a s e s
w ith th e t o t a l w idth o f th e v a sc u la r t i s s u e (xylem and phloem) from
2 mm. to 5 .6 mm.
7.

G rafts were exposed to atm ospheres having r e l a t i v e

h u m id itie s o f 0 , 25$, 50$, 65$, 75$ and sa tu r a te d , a t c o n tr o lle d
tem perature o f 28° C.

R e la tiv e h u m id ities o f 75$ or g r e a te r seem

to g iv e s a t is f a c t o r y r e s u l t s .
8.

G ra fts were made by th e whip method and exposed to

tem peratures o f 0 ° , 1 5 ° , 2 0 °, 2 2 °, 2 4 °, 25°, 2 6 °, 2 8 °, 2 9 °, 3 0 ° , 35°
and 40° 0 .

A la r g e r p er cen t o f g r a f t s exposed t o tem peratures be­

58

tween 35° and 30° C. formed c a llu s than a t tem peratures e it h e r
h ig h e r or lower*

The optimum tem perature seems to be in th e n e ig h ­

borhood o f 28° C or 82° F .
AOKNOWLE3X5EMENTS.
The w r ite r w ish e s t o ex p ress h is sin c e r e thanks to
M essrs. V. H. Gardner, F. G. Bradford and J . W. C r is t f o r many
v a lu a b le s u g g e stio n s and h e lp fu l c r it ic is m s o ffe r e d during th e
p r o g re ss o f t h i s work; and to Mr. W. G. Dutton f o r h elp w ith
p hotographic work.

He a ls o w ish e s to thank Mr. H. M. W allace

and Mr. W. J . F u llilo v e fo r th e cio n wood fu r n ish e d .
Thanks

are a ls o due to th e o f f i c i a l s o f th e U nited

S t a te s Department o f A g r ic u ltu r e f o r p erm ission to con tin u e the
work from 1929 to co m p letio n .
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A. & M. C ol. Bui* B -55.
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61

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52.

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54.

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62

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58.

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59.

W inkler, A. J. Soane F actor’s I n flu e n c in g th e R ootin g o f V ine
C u ttin g s. H ilg a r d ia . 2: 329-349. 1927.

60.

W itt, A. W. The V e g e ta tiv e P ropagation o f W alnuts.
E. M a ilin g R es. S ta . 1926» 26: 6 0 -6 4 . 1928.

61.

W oolsey, C. Pecan Growing and P ropagation in A rkansas.
A g ri. Exp. S ta . S e r . C ir c . 228. 1927.

62.

Woodard, J . S . , L. D. Romberg, and F. J. Wiliman. Pecan Grow­
in g , in T exas. Texas Dept. A g r i. B u i. 95. 1929.

Ann. R ept.
Ark.

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, F ig . 3 - Gross s e c tio n o f a patch bud on walnut s e t by the Kraus
method. Bud f a i l e d t o grow because union was not e s ta b lis h e d
d i r e c t l y under growing p o in t. T his may happen in any type o f
budding.

F ig . 4 - Patch bud s e t by Kraus method which grew in s p it e
o f d ela y o f union d ir e c t l y under bud.

Gross s e c tio n o f a patch hud s e t June 12 and s e c tio n e d
l, 1928. Bud had made growth o f about one in c h .

F ig . 6 - Cross s e c tio n o f a patch bud in which th e bark
u n ited but the bud f a i l e d to grow.

'F ig . 7 - Cross s e c tio n o f a whip g r a ft o f w aln u t. Most
o f o ld xylem in both c io n and sto ck i s dead. The v e s s e l s
are la r g e and not plu gged . O ver-w alling on l e f t and in
c e n te r . D is p a r ity in s iz e o f cio n and s to c k .

m

•

*.

4

F ig . 8 - Cross s e c tio n o f whip g r a ft o f w aln u t. There
i s very l i t t l e c a llu s t is s u e on cio n and th e reg en era ­
t io n in th e tongue o f the sto ck was very weak u n t i l
union became e s ta b lis h e d .

F ig . 9 - L o n g itu d in al s e c tio n o f am putation wound on
pear showing sm all amount o f dead t is s u e and com plete
n ess o f th e p lu g g in g o f c e l l s j u s t under th e wound.

F ig . 1 0 - Gross s e c tio n o f wound on app le ipade by r e ­
moving th e bark and scra p in g th e su rfa ce o f th e wood.
There i s a sm all amount o f dead t i s s u e and very thorough
p lu g g in g o f v e s s e l s , but very l i t t l e wound gum near the
s u r fa c e , which d ied q u ic k ly .

F ig . 11* L o n g itu d in a l s e c tio n o f an am putation wound
on th e w alnut. The dead t is s u e ex ten d s in cone shape
fo r c o n sid er a b le d is ta n c e . The p ith and wood immedi­
a t e ly surrounding i t were dead fo r a space o f about
th ree in ch es below the wound. Wound made June 6 , 1928
s e c tio n cut August 9, 1928.

F ig , 1 2 - Cross s e c tio n o f wound made by hoe in c u l t i v a t i o n . Dead
area exten d s to th e p ith over an area g r e a te r than th e w idth o f
the su rfa ce wound. Very few v e s s e l s are p lu gged . Ray and tr a c h e id
c e l l s a t th e l i m i t s o f th e dead area are p lu gged .

F ig . 13* High m a g n ific a tio n o f th e margin o f the dead area
o f wound shown in F ig . 1 1 . Xylem rays and tr a c h e id s plugged

>*r^
// ftVVV^*V 'iy,

F ig . 1 4 - High m a g n ific a tio n o f s e c tio n shown in F ig . 12
showing t y lo s e s in a few7 v e s s e l s . T y lo se s are found in as
many v e s s e l s o f th e wood formed a f t e r th e wound a s in th e
o ld er wood.

F ig . 1 5 - Cross s e c tio n o f stem below an am putation wound
made June 6, 1928, and se c tio n e d August 1 , showing la r g e
amount o f dead t i s s u e .

F ig . 1 6- Cross s e c tio n o f apple wound showing h e a lin g
by re g en er a tio n in m iddle o f wound and w a llin g over at
s id e s .

Fig,. 1 7 - Cross s e c tio n o f walnut wound showing h e a lin g by reg en ­
e r a tio n in c e n te r and w a llin g over on both s id e s .

.Jig. 19- Final form of constant temperature box; A, thermoregulator;
B. thermometer; G, heater coil; D, basket to hold grafts and packing
m aterial.

7m-.

^////zzzzzzzv////////■ :: ■//iy/s/s/////////,

F ig . 20- The two g r a f t s at l e f t were exposed to tem perature o f 27°
G. and the two at r ig h t were exposed to 30° C. f o r two w eeks. Both
l© ts 7/ere grown in greenhouse bench fo r two weeks lo n g e r and then
photographed* Those exposed to th e h ig h er tem perature had more
f o lia g e of a darker green color*

Cq/ / u ^ eoZ
Cent
Per
ZO

F ig , 2 1- In flu en ce o f temperature on c a llu s form ation ,
p lo tt e d from data o f Table 20,