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POLUNATION

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1892

 
SECONDARY EFFECTS
OF

POLLINATION

BY

WELTON iiARKS MUNSON, B.S.

4

A ThES1S FO R THE DEGREE
OF
MAS TER O F SCIENCE.

1892.
THESIS
-:-:-:-~- OUTLINE. -i-i-i-

Introduction.
I. On the Immediate influence of Pollen on the Mother
Plant.
Il. On the Developement of the Ovary, without Fecundation

of the Cvules,

TIl. On the Amount of Pollen Required for Fertilization; and
the Effects of Pollination on the Form and Size of the Fruit.

IV. On the General Influence of Foreign Pollen, and other
Miscellaneous Observations.

THE SECONDAPY EFFECTS OF POLLINATION.

The change produced by contact of embryo sac and pollen

tube 1s not confined to the mere vivification of one or more
cells; though this is the chief end,- the primary object of all
pollination. There are certain secondary effects which
are of interest te the botanist and may be of great pracitical

value to the horticulturist.
When there is a dit'rerence between male and female

parents, the embryo partakes to a greater or less extent of the
nature of both parents. In general, this influence is appa-
rent first in the offspring of the cross; put in some instances
there appears to be an immediate effect on the ovary or other

portions of the female parent. In some cases also the
Pollen seems to nave a direct stimulating influence on the

Oovarium, without effecting the impregnation of the ovules,
Again, in certain instances the vigor of the plant seems suffi-

“P15231
~ oO.

cient to ceveloyp a marked growth of the ovary in the entire
absence of the male element. The form and size of the ovary
are often materialiy affected by the application of different
amounts of poll.cn to the stigma. In some plants more than

one embryo is developed in a single ovule, indicating the possi-

bility of superfc tation.
These, and other secondary problems arising in

connection with the systematic amelioration of cultivated plants,

are often of great practical importance.

The following notes can be regarded only as
preliminary; as forming a basis from which to start in future
work in this direction. Although some of the problems
considered have been under discusston for more than a century,
they are stili unsolved. There nas not been sufficient sys-
tematic study to warrant the tormilation of general laws, and
this study rast necessarily extend over a long series of years.
In the notes are emrodied as concisely as may be, the more im
portant results obtained by leading experimenters in this country
and in Rurope, together with some observations of the writer on

the subjects in guestion. #

I. ON ThE Pil -SY)TATS INFLUENCE OF POLLAN ON THE MOTHER PLANT.
Even beffore the sexual theory regarding ylant
reproduction was cormonly accepted, the question of the immediate
effect of pollen on the Yorn and character of the female parent
received the atcterition of careful observers, Bradley early
gave directions for performing the operation of crossing and
wrote: "By this knuvledze we may alter the property and taste of
any fruit by impregnating the one with the farina of another
of the same class; as, t'ior example, a Codlin with a Pearmain,
which wili occasion the codlin so impregnated to last a longer
time than usual and be of a sharper taste; or if winter fruit be
| Pecundated with dust of the summer kinds, they will decay before
their usual time". #3

e
— — — -~= ~_e “=
e ® e e

of: ZI wish to acknowledge iny Spectal obligation to
Prof, E.H.Bailey for certain notes and photoxrayns, and tor the
Pree use of his private library.

+ Bradley, New Improveinents in Planting and Garden-~
ing, 7th ed. (1739) p.1s.
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In 1745 Benjamin Cook, in a paper before the
Royal Philosophical Society ,# cited the appearance of russet
apples on trees ordinarily producing smooth fruit, and the re-

verse, as examples of the effect of pollen. Other cases
have been frequently noted as proofs of the existence of the
same phenomenon. 7+ Even at this early date, however,

careful experiments undertaken by Thomas Andrew Knight: and
others, tended to show that the aprarent effects might be due to
bud variation, or other causes aside from the action of pollen.
Knight at this time wrote: #= " I have in some hundred instances
introduced the pollen of one variety of the plum, the pear, the
apple, the cherry, the peach, the melon, and other fruits into
the blossoms of very different and opposite habits, and I have
never, ( although I have most closely attended to the results)
found in any one instance the form, Colomr, size or flavour of
the fruit belonging to such blossoms in any degree whatever
changed or affected."

In 1865 Thomas Meenan opened discussion of the
subject in the colunms of the Gardener's Monthly, remark ng:
"For ourselves, without being satisfied that there is any material
change in the quality of the fruit, we carnot deny there is some;
and there may be much more than we at present imagine.------------
At any rate, we think it may be taken for granted that melons
grewn near squashes often have a suspicious squashy flavour,
that gives some ground for the popular theory of mixing." $
The suggestion is further made that if this change be found to
occur in squashes, the same law wili. apply to the whole region
of fruits ,— -an assumption which is altogether too broad.
There ts evidence which goes to show that within certain limits
there is an immediate effect of the male element, but that those
limits are quite restricted. As early as 1729 the
presence of both white and blue peas in the same pod was observed,
when two varieties of the different colors were planted near each
other. $$ This fact has been repeatedly confirmed. In 1822
examples were presented to the London Horticultural Society.
A variety wnown as Blue Prussian was crossed with a white variety.
The resultant peas were yellowish white like the male parent. $$$
Laxton,in 1866, crossed the Tali Sugar Pea which bears thin green

 

e > e e
—— . nae ° — ° — ° an —_ — — a —-= ° —_ ——> ® =— = —
e s o e e e e ® e .

+ Philosophical Trans. 1745.

* Trans. Lond. Hort. Soc. V.65.
4" Trans. Hort. Soc. V.67.

$ Gard Month VII. 305.

$$ PRilosophical Trans. XLIIIL, 525.
B°8 Trans. Hort. Soc. V. 234.
We -

x

WH aan

 
~ 4 -

pods, with pollen of a purple podded variety. "The pod result-—
ing was clouded with purple, while one ef the peas was of a clear
violet-purple tint and another was irregularly clouded with pur-
ple.” The results, in So far as the changed color of the
peas is concerned, were confirmed by Darwin. #¢

Crucknell # cites an instance of apparent imme-
diate influence in case of the pear. A single branch on a
"Belle Lucrative" tree bore a few specimens resembling “Vicar of
Winkfield. As Vicars were growing near, the conclusion is
drawn that the fruits in question were affected by the foreign
pollen. There is no reason to suppose, however, that this
and the numerous cases of the appearance of russet apples on
trees not usually russetted, are other than instances of bud
‘vartation, as pointed out by Knight. d+

Of about one hundred artificial pollinations
performed by Charles W. Garfield of the Michigan Agricultural
College, but three of the crosses shawed any variation which
could tn any wav he construed as the effect of pollen. “ These
were, First ,— Wagener upon Taliman Sweet,— There was a modifi-
cation of rlavour quite noticeable, the first being sub-acid.
Second, Tallman Sweet upon Astrachan. In this instance there
was a manifest change in the color, flavor and shape. The apples
were quite mild to the taste, the color was very much modified,
and the form was that of a flat ayple. Third, Tallman Sweet
upon Wagener. The modification here was noticeable in all the
specimens, in flavor and color."$

Professor [,.H.Bailey itn 1887, performed many cross-
es with dirfrerent varieties of apples "and got no effect in any
way, mot even tn season of maturity, or in texture." &%
Similar results were obtained by Crozier in 1888. More than
one thousand crosses were made, and they were carefully observed
during the season with a view to detecting any immediate effects,
”" The examination failed to show any differences which could be
attributed to the influence of the cross, ------ In several in-
Stances different varieties were crossed upon the same tree, dut
the resulting fruit’did not differ materially from each other,

f An. and Pits. under Domest. I. 428.
#+# =©6Gard. Month. IX, 165.

+: Trans. London Hort. Soc. V, 67.

$ Gard. Wonth. XVLI1L, 23 (Jan. 1876.)
S$ Proc. Am. Pom. Soc. 1887, 22.
a —— as = ‘o

we >. eed

 

 
- 5 -

or from the remainder of the crop upon the tree." #$

In many species, both wild and cultivated, sports,
bearing fruit differing from the normal type are not uncommon.
Die cious plants of this character must necessarily receive pollen
from an individual of a different character, but as a rule no
effect is observed on the appearance of the fruit of either
individual. A single plant of’ Mitchella repens, bearing white
berries, was discovered by Mr.Meehan and removed to his grounds.
Tmis isolated, it produced no fruit, but in the natural state and
fertilized by pollen from the red-berried form, the white fruit
was produced in ahundance, Prinos verticillatus as a rule
has red berries, but a white verried form on the grounds of
Professor Sargent regularly produced white fruit, though necess-
arily receiving pollen from the red form. +#

On the other hand, instances are cited to show
that there is a marked effe€t on the color of flowers when two
varities of different color are in close proximity. White
verbenas, growing by the side of a pink variety are said to have
produced striped flowers on the side of the plant next to the pink
variety— the other side of the plant retaining the white color.
ane Similar instances of changed color in case
of phlox and petunias have come under my own observation, but in
each of these cases the plants were so situated that the change
could not be construed as due to the influence of pollen.

If polien exerts a modifying influence on the char-
acter of the fruit, we should expect the color of black grapes
to be less intense if fertilized by pollen from white varieties,
than if self-fertilized, or crossed by other dark varieties,

That such influence is douhtful, however, is indicated by the
work of Gorf, of Crozier and others.

Tn 1886, Golf’ crossed several varieties of black
grapes with pollen from a white variety — the Lady Washington.
Other flowers on the same vines were self fertilized. At
maturity it was impossible to detect any difference either of
Color or of flavor between the self fertilized and the crossed
berries of the same variety. $ Similar results were obtained
by Crozier at the Iowa Experiment Station in 1888. %$

e e e . .
e e e e 2 e e © ° se se e e

¥ Crozier, Bul 3. Iowa Ag. Exp. Sta., 92.
+# Gard. Month. XXVII, 116.
#i+: Rerckmans, Am. Agriculturist, July 1889, 344.

$ 5th Rep. N.Y. Ag. Exp. Sta. 180.
$$ Ag. Sci. IL 319.
 

—~- —s-

-_

 

 
-~-6-

The cotton plant furnishes an instance in which
there ts apparently unmistakable evidence of the immediate ef-
fect of foreign pollen. In 1890 at the Georgia Experiment
Station flowers of upland cotton, Gossypium Barbadense (?) were
crossed with pollen from common Okra, Hibiscus esculentus.

Apparently perfect bolls of’ cotton were formed,but in every in-
stance the seed f'ailed to germinate when ;lanted. The reciprocal
cross resulted in apparently normal Okra seeds, but the offspring
varied from the normal in time of flowering and fruiting. $
In 1891 the work was repeated, and Director R.J. Redding in a
private letter to the writer reports, “bolls of cotton, the
result of cotton blooms pollenized@ with okra pollen this year,
in which one and sometimes two of the carpels contained a very
small quantity of lint adhering to the seed while the other divi-
Sions of the ovary were abortive."

It was early observed ## that there is an immediate
visible effect of foreign pollen on cern, extending in many cases
even to the receptacle, and the repeated confirmations by Crozier,
Sturtevant ,#«¢ Kellerman, $ Tracy %$ and others would leave little
doubt as to the accuracy of the observations.

That there is a difference in varieties, in the
readiness with which the influence of pollen is Shown, 1s
altogether prohahle. Sturtevant lays down the general propo-
sition: " Under the conditions of ordinary seed, maize does not
in general show the effects of current cross-frertilization, the
exception being the sweet corns which exhibit the influence of
current foreign pollen very readily." The proposition is based
on the study of about one hundred and twenty five named varieties,
including flint, dent, pop, and sweet corns. That the flint
and dent varieties often exhibit a change the current year, how-
ever, is abundantly proved by the work of the other experimenters
referred to; though all agree that the change is most readily
seen in sweet corn, and least so in the flint varieties. In
this connection, also, Sturtevant makes the statement that: "cross-
bred corn has a greater tendency to current cross-fertilization
than has purely bred corn" 8$$ -—— a condition we should naturally

Exp. Sta. Record, III. 2, 135.
Philosophical Trans. XLVIL, 206.
ord Pep. N.Y. Exp. Sta,. 148.

te

¢ 8nd Rep. Kan. Exp. Sta.., 288-535, (1889)
$$ Rep. Mich. Hort. Soc. 1888, 43.
$$$ 3rd Rep. N.Y. Ag. Exp. Sta., 149.
& eo. oc €=

 

 

 
-7 ~

expect from the verijiatvle tendency of hybrids and cross-breeds.
While there would seem to be no doubdt as to the immediate influ-
ence of foreign pollen in the case of corn, it is not itmprobable
that wnat is in reality seminal effect, may Sometimes be credited
to the immediate action of Poreitgn pollen.

Darwin + cites numerous instances to prove the
existence of an tmrediate efrect of crossing and though some of
the examples to which he yrve credence are now discredited, many
of them are apparently weli authenticated.

Seeds cf Latthiola annua are normally of a light
brown color, whiie those of M. incana are vtolet-blackx; yet
M. annua crossed by wm. incana yielded about firty per cent of
Dlack seeds. Flowers of the orange fertilized by
pollen from a lemon tree produced fruit bearing a longitudinal
stripe of peel having the color, flavor and other characters of
the lemon. Recent observations in this country and in Europe
would appear te confirm the statements regarding citrus fruits .¢+#
Sabine +4 cites an instance in which the form of the ovary of
Amaryllis vittata was altered py the application of foreign pollen
while Maximowicz made reciprocal crosses between Lilium bulbi-
rerum end L. davuricum and found " each species produced fruit
almost identical with the pollen bearing species." $
Fritz Miller crossed Cattleva Leoroldi by Epidendron cinnabari-
anum, and obtained a marked charge in the form of the seeds .%$

Rhodocerdaron dalhnousiz crossed by Rhododendron
Nutallt:, is cited by Darwin as an example of the increased size
of ovary resulting from the action of foreign pollen, while Arabis
blepharoyhvlla crossed by A.soyert produced pods larger than
either parent species, #88

Darwin also gives credence $588 to the story of the
St .Valery apple, the stamens of which are abortive, and being
artificially pollinated, the fruits are said to differ from one
ahother in size, flavor and color.— resembling in character the
various kinds by which they have bveen fertilized.

—

 

 

 

— —_ — —_ -— — ~_— —_ —_ — — -- -o

An. and Plts. under Domest. I. 428 et.seq.

a See Repts. Am. Pom. Soc. 1889 and 1891.

Ae Trans. Lond. Hort. Soc. V, 69.

$ Darwir,. An. and Plts. under Domest. I. 481.
$$ Ibid.

KER Darwin, An. and Plts. under Domest. I. 432.

SESS Ibid.
a

~gs8-

In the cultivation of pistillate varietigs of
strawberries, it is usually considered necessary to set some
variety with well developed stamens in the immediate vicinity to
furnish the pollen requisite to the fertilization of seeds, and
comsequent development of the receptacle. It is believed by
many growers that the character of these pistillate varieties
may be varied at will, by using different varieties for the male
parent. In other words, it is believed that there is an im-
mediate effect of the male element in determining the time of
maturity, the color, the shape, and even the flavor of the recep-
tacle of the variety erossed. If this theory be based on
fact, it is of no small practical importance. If it were true,
that in all cases, or that as a rule, the fruit partook of the
character of the male parent, there could be no fixed character
to any pistillate variety. But wili the facts warrant the
assumption that this immediate effect in the case of strawberries
Is bY any means universal, if common?

Personally I have’ conducted no work bearing upon
this yoirt, but several experiments have been performed by care-
ful observers, arc the results obtained by them are of interest
in this connection. The results as rublisned dirfer consider-
ably, but in general, the weight of authority goes to show that
the receptacle is not materially affected by the male element,

At the meeting of the American Pomological Soctety,

in 1885, | extended and spirited discussions of tnis subject
were held. Professor W.R. Lazenby, of the Ohio Experiment
Station, had found the influence of the male element decidedly
manifest, When blossoms of Crescent were fertilized by

pollen from Downing, Vick, or Sharpless, the characteristic shape,
texture and other qualities of the male used were impressed on
the receptacle to such an extent that it was possible to deterinine
the male parent.from the general appearance of the crop. # A
repetition of these experiments the following season, however,
failed to give any marked results. ##

From an extensive field experiment conducted by
Professor T.J. Burrill in 1884, it was found "easy enough to se-
lect individual berries conspicuously different from each other,
as 1s always the case, but it was not possible to detect the
Slightest tendency towards a resemblance tq the pollen bearer."
PPP
+ Proc. Am. Pom. Soc. 1885, 66.
#f Rep. Ohio Exp. Sta. 1885, 107.
tit Proc. Ain. Pom. Soc. 1885, 67.
e

~9-

In a Similar experiment conducted the following
year on the farm of P.M. Augur of Connecticut, like results were
obtained. #

In mone of the carefully conducted experiments of
Goff and Hunn at the New York Experiment Station, have any imme-
diate effects been discerned. Berries from Crescent blossoms,
receiving the rollen of Lennig's White, were not different in
color from those fertilized with Wilson or Sharpless pollen.
Flowers fertilized on one side by pollen f'rom the white variety,
and on the other with Sharpless pollen were symmetrical in form
and uniform in color. ##*

Out of one muindred and sixty seven successful
crosses made hy Crozier, there was not an individual instance
that pointed to a specific influence of the foreign pollen. ++

On the other hand, A.S. Fuller who has made a
careful study of the subject since 1859, claims to have obtained
very marked indications of an immediate directing influence on
the form and size of the receptacle. 8 Mr.Fuller attributes
this apparent influence to the direct action of the pollen in
stimlating the growth of the ovary or receptacle without reference

to the fertilization of the ovules. Admitting the stimlat-
ing effect, however, — and of this there seems to be little doubt
— does the directing efrect necessarily follow? The question

 

Is stili an open one, out the results obtained from our work with
eucurbits, with tomatoes and with exyg plants, as well as the
published results obtained py other observers, would point to a
negative answer.

The nature of cucurbitaceous plants is admirably
adapted to show the immediate effects of crossing if such occur.
In a mtxed plantation many of the flowers on any individual plant,
when left to natural processes would necessarily receive pollen
from very different sources. If now, there were an immediate
effect of pollen, we should expect to find fruits of very diifer-
ent character on any given vine. Such is not the case, how-
ever. I have repeatedly looked for this difference
but have never seen it; nor have I observed it when several
flowers on the same plant were artificially crossed.with pollen
from different varieties or species. Crozier and Bailey have
repeatedly obtained like results. Bailey, whose crosses

e e ®
~- ° ~. ° es . —_- ~— —_ ° ~ — ad —_ ® os ® ==
e e oe s e

1885, 70.

Proc. Atm, Pom. Soc.

¢ 4th Rep. N.Y. Agr'l. Exp. Sta. (1885) 227; 5th Rep. (1886)
_ 179; also Bul 24 (N.S.) 380 (1890).

PRE Ag. Sci. IV. 287.

#
$ Proc, Am. Pon. Soe. 1885. 68.
me, EOS

of cucurbits run up into the thousands, asserts positively that
“there is no immediate influence whatever, except such as 1s due
to imperfect development caused by insufficient or tmpotent
pollen." #

In our own work with tomatoes and egg plants there
has in no case oecurred an instance of immediate effect other

than alteration of form due to insufficient pollen. During
the past winter numerous crosses and hybridizations of tomatoes
have been made. Thea accompanying photographs of the most

violent of these crosses indicate the entire absence of apparent
effect.

Figures 1 and 2 represent the"Lorillard", crossed
by pollen of the "Currant", —— (Lycopersicum esculentum X LL.
Pimpinellifolium). The Lorillard is a smooth, nearly spher-
ical variety of medium size, and as grown under glass seldom weighs
more than three or four ounces.

 

+ Bul. 25 Cornell Univ. Exp. Sta., 181. ( Dec. 1890).
6

 

 

Figure 2.

As will be seen, the fruit is in every respect
typical of the Lorillard. The offspring from this cross, how-
‘ ever, show uninistakable evidences of the influence of the male
parent, both in the habit of the plant and in the character of
the foliage and flowers.

Figures 3 and 4 are photographs of a cluster in
which each fruit has a different male parent. As in the
other case there is no apparent. ef€ect on the form of the fruit;
and the seeds gave no indication of different parentage, —- all
were apparently typical Lorillard seeds.

In the offspring, the differences are very markea@,
The lines are sharply drawn between the crosses with Peach and
Currant, while the Lorillard is apparently unaffected by either
of the others, —— indicating that there was no error in the
operation, also that there has been no transfer of influence \
along the short interval between the peduncles.
a EO

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ee

 

 

 
*h
ed

 
In an exterded series of experiments with egg
plants, conducted for three consecutive years at the Cornell
University ana the Maine State College, the most widely varying
types have been crossed. In no instance, however, has there
appeared an immediate effect of the male parent. The littie
Round White, when crossed with pollen froin Black Pekin, diifere@
fm no respect from other fruits on the same plant. But the
offspring of this cross snowed very marked variations. The same
facts were onserved regarding several other crosses .#¢

As before noted, instances have been reported,
in which the color of flowers was aj}. arently changed by the action
of foreign pollen the current season, An instance of such
change has never come under my observation, though I have made
numerous crosses of different varieties of Trop&@olum, Fuchsia,
Silene, Phlox, Petunia, and other ornamental plants.

As indicating the range over which the study of'
the sunject has extended, a partial iist of the species consider-
ed by difrerent observers 1s given:

 

Species in which immediate influence of polien is said to
¥ have been observed:

Amaryllis vittata

Arabdis pvlepnaropnylla.

Cattleva Leopoldil

Citrus Aurantium

Gossyplum Barcadense. ( sp. 2). ##
Lilium bulbdiferum

Lilium davuricun

Matthtola incana

Phaseolus vulgaris

Pisum sativum

Rhotzocandron dalhousie&

Verhnena sf.

Zea mays.

» # Bailey & Munson, Experiences with @g Plants, Bul. 26.
Cornell Exp. Sta., p. 14.

## The common "Upland" or "Short Staple cotton and the "Sea
Island" cotton are usually classed as varieties of G. Bar~
badense, vut some authorities regard them as distinct
Species.
wr ¢

—~.

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wr

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- 414 -

Species in which no immediate effect appears to occur:
Cucumis melo.
Cucumis sativus.
Cicurbita maxina .
Cucurbita imoschata.
Cucurbita pepo.
Datira Stramonium.
Natura inermis.
Fragaria virginiana.
Lycopersicumn esculertun.
hycopersicun piyrpinelLiProlium.
Mitchella repens.
Prinus Americana.
Prinos verticellatus.
Pyrus imalus. |
Pyrus Torringo.
Pyris Soulardti.
Vitis lanrusca.
Petunia violacea.
Phlox Drummondii.
Silene arvertia.
Tronp® ola minas.
Puchsta sp.-

Mie anove lists are probably incomplete, and mst
necessarily he regarded as tentative. As yet there are no
satisfactory data on which to base general conclusions. It
would be unwise at the present time to assert that the directing
influence of pollen does or does not as a rule extend beyond the
fertilization of the seed. It seems not improbable that
pollen trom a vigorous plant, may make an imprint of its character
on the female organism which shall ve different from that of a

less vigorous male parent. It 1s probable, however, that the
vigor and inherent vitality of the plant operated upon usually
determines whether this ne manifested, Some species show

apparently unmistakable evidence of the influence of foreign
Pollen, -— this is notably the case with peas and Indian corn.

On the other hand, cucurbitaceous and solanaceous
plants seem to resist all foreign influence; while rosaceous
Plants are in dispute, with the weight of authority tending to
Show the absence of immediate influence.
-j~ 15 -

Il. ON THE DEVELOPMENT OF THE OVARY WITHOUT FECUNDATION OF THE
OVULES .

A common, though rot universal law of reproduction
by seed requires fertilization of the ovules as a condition
necessary to the development of fruit. It is a matter of
common observation that, as a rele, when pollination fails to
result in fertilization, or when pollen is withheld, not only
the pistil withers, but the entire flower decays and falls.

( Pollination is used in the sense of céSition in the animal king-
dom and does not necessarily result in impregnation). Instances
are not infrequent, however, which point to a responsive action
on the ;art of the pistil or other portions of the flower receiv-
ing pollen, while from an insufficient quantity of pollen, lack
of affinity on the part of the species crossed, or some other
cause which remains to be determined, fertilization does not
occur. Examples of this are specialiy common in all of our
cultivated fruits and vegetables.

About the close of the sewenteenth century, (1691),
Camerarius had observed # that a feinale mulberry tree once bore

Y frit though no male tree was in its vicinity. The berries,
however, contained only abortive seeds. Plants of Mercurialis

annua heing then nrought under observation, it was noticed that
While the fruits were abundant and well rilied out, they vegan
to wither when about half ripe and not one produced perfect seed.

The instance of the imilberry is confirmed by
Claypole who cites ## a case within his own observation in which
a pistillate tree pears fruit abundantly every year though no
stamirate tree is in the vicinity, and no staminate flowers have
been found on the tree itself. che “seeds" in these fruits,
as in the other instances, contain no empryos. Whether this
Is a case of development in the entire anserce of pollen, as
Circumstances would indicate, or whetner there may have been a
limited suprly of polien at hand, it is evident that the ovaries
developed independently of any action on the ovules.

Dr. Masters is authority for the statement that
certain varieties of pears nanitually produce seedless and core~
less fruit. #4 In the same way it is not uncommon to find the

y Capsule of many herbaceous plants fully developed while the seeds

R.J. Camerarit Opuscul@a Botanici Argumenti, cited by Sachs —
Hist. of Bot. 386.
Rep. U.S. Dept. of Ag. 1887, 318.

Nature, 4XXV, 12. (Nov. 4, 1886).

: ~
ad
sia
~ 16 -

are absent. M.Jean Sisley, a well known Frencn horticulturist,
found this to occur with great frequency in case of the geraniums
and pelargoniums. OF one hundred flowers of Geranium ylaty-
petalum artificially pollinated, not one yroduced perfect seeds,
and of a large number of capsules sent py another party, nearly
all were without seeds. #

Naudin as a result of his studies of the genus
cucurbita suggested the possibtlity of a specific effect of
pollen in exciting growth of the ovary, and tnis theory is sup-
ported by Focke who Says: “Pollen has two actions on the female
organs, one on the seeds, and one in exciting the growth of the
fruit.” #¢ The theory seems plausible, and in view of
the many examples of well developed but empty seed pods, it would
seem that the stimulating action is alone exerted in some instances.
These examples are specially Common among peas and beans.

The accompanying y~notoxraph, Figure 5, represents
the natural size of a Lire pnean whicn failed to develop seeds, —
the undeveloped ovules may ne seen at the right.

According to Hildebrand tn the case of several
orchids, the plant’s own polien is necessary for the development
of the ovarium; and this development takes place long before the
pollen tubes have reacned the ovuleS. t-« So in these cases
the polten acts dtrectly on the ovartun.

Gard. Chron. N.S. EV, 654.

## Rocke, Die Pflanzen-Mischlinge. 447.

###+ Botanische, Zeitung, No. 44 et. seq. Oct. 30, 1863 and
Aug. 4, 1865, cited by Darwin, An. and Plts. under Domest.

I, 434.
Sars

 

 

Figure 5.

Disregard of the fact discovered by Camerarius,
but not emphasized py him, that certain diccious plants occas-
lonally have mone cious individuals, has led to many erroneous
statements regarding the influence of the male element on the
ovary. Hemp and Spinach have been cited # as examples of
development without fertilization. It is well known, how-~
ever, that both of these species have mone cious individuals,
thus furnishing a source of error in observation.

The imiskinelon, Cucumis melo, is another instance
in point. This fact first attracted my attention when at~
tempting to perform some artificial hybridizations between
Cucumis melo and Cucuthis sativus. The female blossoms on
the variety under consideration ("Emerald Gem") were found to
bear partially developed stamens. These stamens varied in size

« .
ae ~ -_ -—- ft - _— -_-s-

# Le Maout & Decaisne, — System of Botany, 152.
‘

a

 
~ 18 -

and in the amount of pollen produced, but subsequent developments
indicated that enough policn may be produced to secure self-
fertilisation. —— In these cases of’ probable self-fertilization,

however, there were no perfect seeds,
Darwin cites, on the authority of Dr.Hooker, an

instance of the development of the ovarium of a certain orchid —
Bonatea speciosa — as a result of simple mechanical irritation
That under certain conditions the ovary

of the stigma. #
of some species may develop to a considerable degree entirely

without the intervention of the male element seems to be beyond
question, What the conditions are which insure this phenom
enon is as yet uncertain. Exceedingly vigorous growth of the
plant ts certainly a first requisite, nut there also seems to be
an indtvidual variation in this direction, with some species.
The fact that in growing English forcing cucumbers
for market, garderers never practice artiticial pollination, as
is necessary with the varieties commonly grown in this country,
raised the question as to whetner any pollen is required, and
what proportion of the fruits would develop without fertilization.
Several diiferent varieties have been under consia-
eration at different times. In case of the "Telegraph", a
long Slender variety, more than twenty blossoms were covered with
paper bags before expanding — thus preventing all possibility of
the access of pollen. Out of this number, but two developed
fruits. These were typical in form and of average size, — he-

ing about sixteen inches long and two and one half inches in
They contained a large number of partially develop-

~ sone of them 3/3 inch in length extending

There were no perfect

Ctameter,

ed ovules
nearly the whole length of the fruit.

seeds, however, as shown by Fixture 6.

 

 

af An. and Plts. under Domest. IL. 434.
- 19 =

 

 

Figure 6.
eras

ms, known as "Sion house", covered
Later many other blossoms were

Covered and some fruits were developed, but the percentage was

age
Of ten blosso
as above, one developed fruit.

about the same as before. The fruits, as with the "Telegraph"
were straight and smooth and contained an abundance of partially
developed ovules along the whole length of the fruit; but there
were no perfect seeds.
Other frutts of both varieties, left to natural
conditions, were examined and as a rule were found to contain
no verfect seeds. Indeed, this absence of seeds is a matter of
Common observation, and 1s urged as a point of excellence in favor
of the English varieties. In one instance two or three
apparently good seeds were found, but no embryo was present,
while most of the ovules were only one eighth to one fourth inch
in length. There are few, if any, insects in a forcing house
in mid-winter, which would be likely to carry pollen; and it is
probable that fruits left to natural conditions received no pollen.
Other varteties exhibit characteristics peculiar
- 20 -

to themselves, when pollen is withheld. "Blue Gown", for ex-
ample is almost invartably withered and shrunken at the apex or
"blossom end", as Shown in Figure 7, The same tendency is
shown by the " Duke of Edinburg". No seeds are developed in
these fruits, and at maturity they are often hollow at the lower

end, as shown in Figure 8&8.
In several instances I have observed the develop-

ment of fruita on the "Duke of Edinburg", when the blossom never
expanded. One of these is shown in Figure 9.

 

 

Figure 7.
 

Figure 8.

 

Figure 9.
warty a,

ee.

~

n—7

a. oe) ~e

 

 
—- 22 -

In our studies of the egg plant — Solanum melon—
gena, etc. — we have at different times secured well developed
fruits from blossoms which had been castrated and covered with
paper bags to prevent access of roreign pollen. In no case
have perfect seeds been found. The first instance
noted was in the summer of 1890, and the fact was published the
following spring. # During the past winter, 1891-2,
experiments in this line have been repeated on plants growing in
the house. Out of Pifteen Dlossoms emasculated and covered,
two apparently good fruits developed. One of these when
about six weeks old began to decay, and was picked, and photo-
graphed — see Figure 10. The other, at the present writing
is still growing.

 

 

y rae , iz % ath
Re Se HR at

 

Figure 10.

As will be observed, the outer portions of the
» fruit grew mich more rapidly than the inner, — the placentze
- evidently requiring the stimulus of the growing ovules to induce

¥ Bailey & Munson, Experiences with Yss |lants, Bul. 26,
Cornell Exp. Sta. 19.

 
 

 

 

‘

 
—~ 23 -

development. The abortive ovules are seen at a, as minute

brown particles. A very few of them — ten in the whole fruit
— were partially developed,- indicating the possibility of a

few grains of pollen naving reached the stigma. The work

was very carefully performed, however, and I am confident there

is no error.

It is interesting in this connection to note the
fact that these fruits have usually developed on cross+bred
plants, rather than on fixed varieties,— a fact apparently in
accord with the supposition before expressed, that excessive
vigor of the plant is a prime requisite for the appearance of the
phenomenon.

A further indication that excessive vigor of
growth may affect the fruit, is in the abnormal development of
the calyx of the egg plant in many instances,while the growth of

the ovary is arrested. Usualiy the most prominent indication
that impregnation has taken place, in the exyxy plant, is the rapid
growth of the calyx. Many times, however, the calyx becomes

mich enlarged while for some reason the ovary fails to develop.
I have frequently seen examples of this, in which the calyx was
fully six inches long.

Another tnstance otf the partial development of the
ovary was observed ir a Summer Crockneck Squash to which pollen
of another variety was aypylied. The fruit attained about
elght tnches in length, and remained in this condition during the
season, No perfect seeds were developed,

From the evidence adduced the fact seems well
established that the ovary may develop and reach normal size
without the corresponding impregnation of the ovules, and even in
the entire absence of the male elenent. What the conditions
are wich induce this apparently abnormal condition, is not fully
determined. Jt ts evidert, nowever, that vigorous growth of the
parent plant is of first tmportance.
- 24 -

111. ON THE AMOUNT OF POLLZN REQUIRED FOR FERTILIZA-
TION; AND THEE EFF=CTS OF POLLINATIGN ON THE FORM AND SIZE OF THE
FRUIT.

Ke lrepter .# in 1761-66, found that with Hibiscus
venetianus , fifty to stxty polien grains were suftricient to pro-
duce more than thirty fertile seeds in the ovary. In
Mirabilis jalapa, and M. lorgiflora, which have a one ovuled
ovary, two or three, anc in some cases even one grain was suffi-
cient for fertilization. Now, according to Koelreuter, the
Hibiscus rrocuced 4863 roller prains in a single flower, — or
81 times more thar needed for actual fertilization. So also
the Mirabilis produced about BCC grains, or from 100 to 200 times
too mich. It aprears therefore that there is no relation
between the amount of yollen produced py a plant, and the amount
required tor fecundation.

Since the time ot Koelrerter, little has been done
toward determining the actual mimber oi grains required for the
fertilization of any given spectes; but the fact has been plainly
demonstrated that the amount of polien applied may have great
practical importance in deternsining the form and size of the
fruit, as well as the quantity of fruit produced,

In crossing stravperries at the New York Agricul-
tural Experiment Station, #« the ract was plainly brought out that
the proportion of berries secured depends upon the abundance of
the pollen furrisscd py the variety used as a fertilizer, — a
point which is of great moment if the same law holds under natural
conditions. That there may be some doubt of this, however,
1s indicated ny the fract that certain so-called pistiliate varie-
ties ——- notably the crescent — at times mature fruit and appar-
ently perfect seeds in the aosence o8 any perfect flowering vari-
ety.

 

 

One prower ol ny acquaintance uses no perfect
flowering variety, and succeeds admirably. I have never seen
these ylants, hut it is well known that the pistiliate varieties
Prequently produce jlants having partially developed stamens,
and it is probable that by unconscious selection, plants of this
Character have been increased to a considerable extent. In any
case, the amount of pollen is necessarily quite limited.

+ Cited py Sachs, Hist. of Bot. 408.
Pe 86Sstth An. Rep. N.Y. Ag. Exp. Sta. 199,
«g

~ 95 -

That the amount of pollen used inray have an import-
ant bearing in determining the form and size of the fruit is
certsin. This fact, which is of special importance to the
horticulturist, iS Snervn by our work with tomatoes,

Tn the winter of 1396-91, while crossing tomatoes,
two stigmas in the same cluster of flowers, were viven diiferent
amounts of pollen. The tirst was given a very small amount —
ten to twenty grains — on one side of the stigma; the other was
given an excess of yfolien, the stigma being well smeared.

The effect on the form and size of the fruit was very marked.

The fruit receiving the large amount of yollen was of normal

size and nearly symmetrical in form: whiie the other was small
and deformed. fhe larger fruit developed an abundance of seeds
and ali of the cells were weli developed; the smaller developed
seeds on one side only, while the other side was nearly solid.

Puring the vast winter the experiments have neen
rereated many times ana the results have peen untYormly similar
to those detailed.

In tne Vrirst ease,— see Figures 1l and 12 — the
flowers nearest the pase of the cluster received an excess of
pnolien, while the otner received a very smaii quantity on one side

of the stixgina. In anotner instance,— see Figures 13 and
14 — the Ylower at the base received the smali amount of pollen,
while the other was yviver an excess. Similar results were
obtained, indicating that the relative position of the flower has
no influence tn determining this point. As will be seen from
Fizure 14, the seeds in this instance — but ten in mumber — were
all torn in one cell, and the deformity of the fruit was corres-
pondingly greater than in other cases. The @ditference in

Size of the fruits was even greater in some instances than in
those already cited, as seen in Frizure 15.
—- 26 -

 

 

Figure 11.

 

 

Ticura 19
27 -

 

Py t
=

Figure 13.

“
PE th.

rm 4

s
~~
>

.

“

 

ure. 14,

rig
(WB 1897-2. %
oo rhlrd .

nie . Exces 2.

   

Firire 15.

The exact munber of pollen grains necessary to
insure partial development of the ovary, in case of the tomato,
I am unable to state at the present time. Certain it is, however
that the secondary actions of the pollen in stimilating the growth
of the fruit is of no small importance. No doubt the greater
development of the one side is largely due to fertilization of
the ovules and the consequent growth of the placentae; but that
there ts a further cause is indicated by the partial growth of
the other side.
Whether these results point to the possibility of
securing seedless tomatoes by reducing the amount of pollen em-
ployed, is questionable. In no case have we secured fruit
when all pollen was excluded, and in every case the size of the
fruit was in direct proportion to the amount of pollen used,

By careful selection we have secured tomatoes with
relatively very few seeds; and Professor Bailey reports absolute-~

ly seedless fruits. # It is very doubtful, however, if these

° = s - - - =
~ _— ° .

# Rep. Cornell Univ. Exp. Sta. 1891, 55.
- ?9 -

fruits can be regarded es anything but variations. The habit
of the plant has become so modified that the influence of the
pollen in stimilating growth is stronger than its fecundating
power. In none of the plants bearing relatively seedless
fruits, was there an apyarent lack of pollen.

A further instance of a inodified form of the
fruit as a result of pollination was observed with the English
cucumbers, As a rule, in cases of articifial pollination,
if the fruit developed at all, the apex was mich enlarged and per-
fect seeds were developed,— these seeds usually extending about |
one third the length of the fruit. This result I have |
found to be almost invariable with some varieties, — notablg the
"Telegraph", of which an example is shown in Figure l6.

 

Figure 16.
—- 40 -

This peculiarity or Yorm ts the uSual result of
rollination in other varieties also; but it is not invariably
the case, and Professor Hailey revercs the irregular f'orm as "an
expression of plant variatton, rather than a result of particular
treatinent ." # Certain individuals may be more susceptible to
the influence of pollen than others, but as the variation is trace-
able directly to the action of pollen in the impregnation of the
ovules, the subject may properly be considered in this connection.

the reason for the failure of seeds to develop
throughout the length of the ovary, in the lone Englisn cucumbers
sas yet wneertain. It appears yprobanle, however, that the
egplanation lies in the extreme lergth of the ovary and the
consequent tnantlity of the yolien tubes to penetrate so far.
There has been a variation in the ovary without a corresponding
variation in the pollen. The amount of pollen applied appears
to have little effect in regard to this point.

In general, while little accurate work has been
done in the way of determining the exact amount of pollen néc-
essary for fertilization, it appears tnat the question has hear-
ings of much practical importance. In some instances the size
of the fruit seems to be in direct proportion to the amount of
pollen used, while the form 1s much improved by an abundant sup-
ply. In some cases, on the other hand, fruits will develop
without the intervention of the male element, and the pest results

are obtained wnen pollen is withheld.

$ Bailey, Bul. 31, Cornell Univ. Exp. Sta., 137.
- 3] -

IV. ON THE GENERAL INFLUENCE OF FOREIGN POLLEN, AND
OTHER MISCELLANEOUS OBSERVATIONS.

AS already intimated, polien appears in many cases
to act directly on the ovary, stimalating growth of that organ
independently of any effect on the ovulés. This faet is most
clearly seen in those species which do not readily cross.

In this connection, Focke remarks: "The pollen of
the specics acts quicker than foreign pollen and 1s alone effect-
ive 1f mixed with foreign pollen upon the stigma.” --------------
"It is probable that if the pollen of the species is insufficient,
Poreign pollen may serve to develop the fruit, and thus serve a
purpose." Some instances strongly supporting this pro-
position have come under my observation. One of the large
mnglish cucumbers, "Duke of Edinburg" was given pollen of the
“Binerala Gem" miskmelon. {In this case then, we have cucumis sat~

 

jivus crossed by cucumis melo). The cross was made in Febru-
ary. The resulting fruit attained about one half the usual
size and then ceased growing. When the vines were torn from

the house, in June, this fruit was stili green while other fruits
receiving pollen of the species two months later were fully
raature, The ovules in the fruit in question were wholly
undevelored.

Two other instances of a Similar nature were ob-
served. The tirst of these was tne common Summer Crookneck
Squash crossed by the"Anerican Turban" — Figure 17—; while
the second was the same variety crossed vy "Mammoth Tours" Pump-
yin, — Figure 1&8 .4¢ In both of these cases the fruit develop-
ed, as indicated, about six inches in length, and remained in
that condition several weeks.

A most remarkable instance of secondary inf'luence

of foreign pollen is that recorded by Lowe, ++ Flowers of
the yellow musk plant, Mimulus lyteus were crossed with Mimulus
Sashacrianus, which nas spotted flowers, When the pods from

these flowers were nearly matured, other flowers upon the same
branches were given pollen of M. luteus. More than one hundred

# Die Pflanzen-Mischlinge, 448.

2%- The two crosses last named were made by Professor L.H. Bailey
at Cornell University. All other illustrations are from
work performed by the writer.

tj E.J.Lowe, Rey. British Ass'n for Adv. of Sci., 1885, p.1087.
a ae

ye

a BO

 

 

Figure le.
—- 43 -

seedlings were grown from these latter crosses and every one bore
- spotted flowers. In other words, the influence of the pollen
of the foreign species was transferred along the branch and
overcame the influence of pollen from the same species.

This result is in direct opposition to Focke's
principle of the prepotency of pollen of the species as compared
with foreign pollen, and as vet, so far as I am aware, Lowe's
statements have not been verified. I have undertaken to prove
the truth or falsity of the statements but have rot as yet
reached conclusions,

SUPERFG: TATION: Is 1t possible that the progeny of any plant
may be in any way affected by the application of foreign pollen
to the stigmas after self-fertilization has already taken place?
Is it possible to obtain distinct effects from two male parents
when the pollen is applied at different times? Comparatively
little has been done toward solving these questions, and they
are suggested as promisirg lines of investigation rather than as
sudjects for extended discussion at this tine. Both Gray *# and
Focke ys have deriecd the possitility of superfcetation, put
other observers have cited instances in support of the theory and
certain facts nave come within my own observation which point to
the possibdicity of several seeds in the same ovary being the
product of different tmnale pareritage.

Grieve in 1874 y= individually pollinated several

 

 

blossoms on some plents of Pelargoniun peltatum. One of these
plants was on the day Poliowing given pollen of Pelargonium
zonale. The offspring of the rirst plant were all true Pelar-

gonium peltatum, while of the offspring of the second, no two
were alike, the leaves of’ some being large and of others small;
Some showed a well developed zone, while others were without any
indications of this character,

Charles Arnold in crossing corn, used pollen from
both a yellow and a white variety on pistils of a dark purple
sort. The resultant grains were yeliow at the base and white
at the top; while those of another ear on the same stalk, being
individually pollinated, were of normal color.$ This instance
established in the mind of Mr.Arnold the fact of the possibility
of superfoe tation, and was used by Thomas Meehan $$ as the basis
for an argument in support of the theory of the immediate influ-

, eo e *
-—- =_— own =—_ o- = ean — —_ = a=- => =_ — -—, =
o e e e e e e e e

Am. Jour. Sei. and Arts, KXV, 123.
Die Pflanzen-hischlinge, 448.
Gard. Chron. N.S. Vol II, 689.
Gard. honth. XV, 104,

Proce, Prta., Acac, Set. 106756. 16.

athe
~ 44 ~

ence of foreign yolien as wel: as of’ the theory of superfoe tation.
In applying smali amounts of pollen to the stigmas
of tomatoes, I have observed that the portion of the stigma
receiving pollen soon turned brown and withered, while the other
side remained green and in an apparently receptive condition
for some time. This fact was specially apparent in the fruit
shown tn Figure 14. As seeds develop only on the side re-
ceiving pollen, it seems probable that seeds on the other side of
the ovary might well be fertilized by polien of a different varie-
ty or svecies.

CONCLUSION.

Darwin, Wallace, Weismann and others have studied
the laws of heredity, and nave arrived at conclusions of vast
importance in the systematic amelioration of plants. At the
present time, however, but little is known of the laws controll-
ing the numerous secondary results attending the crossing of
plants. From the evidence at hand it appears that the second-
ary results may ve of fully as mich importance as are directly
inherited qualities.

The collateral inheritance of qualities is by many
absolutely denied, and there is mich evidence in support of this
position. There are instances, however, which strongly sus-
tain the other side of the question, and it is probable that the
truth lies netween tne two extremes.

That polien has a cirect stimlating effect on the
ovary, independently of its action on the ovules, seems a well
established fact. In many cases the size of the fruit is in
direct proportion to the amount of pollen used; but it is also
true that in many cases the fruit may develop to its normal size
in the entire absence ot the male element.

Vrether suyerfe tation is possible, is a question
of no sinall importance, but the evidence is as yet insufficient
for conclusions to be drawn.

With eli cultivated plants, however, there is an
inherent tendency to revert to ancestral forms and this is a
Source of error to be guarded against in attributing certain
results to rictitious causes,
mk

OB a

Co US eemmar pale reba, ~-— f
PANN SE ONLY

 

 
 
 

 

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