CLIMBING PLANTS.
BY PROF. W. J. BEAL.

THE following remarks upon this interesting subject, can
scarcely be called a review, but more properly a summary
given nearly in the words of the author .* It has been made

*On the Movements and Habits of Climbing Plants. By Charles Darwin, Esq.,
F.R.S., F.L.S., etc. [From the Journal of the Linnæan Society.] pp. 118. London, 1865.

406
quite full, as it is likely the original paper has been read
by but few readers of the NATURALIST.
Climbing plants may be divided into those which spirally
twine round a support ; those which ascend by the movement
of, the foot-stalks or tips of their leaves; those which ascend
by true tendrils; those which are furnished with hooks, and
those which are furnished with rootlets. The last two exhibit no special movements and are of less interest than the
first three.

Spirally Twining Plants .- I begin with a special case,
one depending upon my own observation, similar to the one
taken by Mr. Darwin. A thrifty hop-vine in my yard went
up nine or ten feet to the top of a stake. Still aspiring it
ran above the support, at the same time reaching off and
swinging round and round following the course of the sun.
When about two feet above the stake the tip of the vine circumscribed a circle two feet in diameter. While it grew
longer the extent of the circle was about the same, as a
part of the vine had become strong and remained nearly
stationary. By observations made at different times in the
day it was found to perform one revolution in from one to
two hours, moving most rapidly in the warmest part of the
warmest days. It is now four feet and two inches above any
artificial support, and has just tipped over to the north-east
in the direction of the prevailing wind. The revolving
movement lasts as long as the plant continues to grow,
but each separate joint or internode, as it grows old, ceases
to move. In the case of the hop and most other twining
plants, about three internodes at a time partake of the
motion.

The Hoya carnosa (Asclepiadacec) revolves opposite to
the sun in five or six hours, making a circle of over five feet
in diameter. The tip traced thirty-two inches per hour.
It was an interesting spectacle to watch the long shoot
sweeping night and day this grand circle in search of some
object round which to twine. Sometimes it described narrow 

407
ellipses. After performing thirty-seven revolutions the
stem of a hop was found to be twisted three times round its
own axis in the direction of the sun. To prove that the
twisting of the stem does not cause the revolutions, as Hugo
von Mohl supposed, some stems are not regularly twisted
and others twist in an opposite direction to the revolving
plant. In many twining plants the end of the shoot is
hooked so as the more readily to hold fast to any object of
support which may be caught. This support once found,
the point of contact ceases to move, but the tip continues to
twine above and around the support as a rope swung around
a stick will coil in the direction of the swinging rope.
If a stick shortly after having been wound round be withdrawn, the shoot retains for a time its spiral form, then
straightens itself and again begins to revolve. Mohl believed that plants twined because of a dull irritability of the
stem, but experiments prove that this is not generally the
case.

If the support of a twiner be not lofty it falls to the
ground, and resting there the extremity rises again. Sometimes several flexible shoots twine together into a cable and
thus support each other. Single thin shoots will fall and
turn abruptly back and wind upwards on themselves. The
majority of twiners move in a course opposed to that of the
sun or the hands of a watch. Rarely plants of the same
order twine in opposite directions, but no instance is known
of two species of the same genus twining in opposite directions. Of seventeen plants of. Loasa aurantiaca, eight revolved in opposition to the sun and ascended from left to
right, five followed the sun and ascended from right to left,
and four revolved and twined first in one direction, and then
reversed their course. One of these four plants made seven
spiral turns from right to left, and five turns from left to
right. Climbers of the temperate zone will not generally
twine around thick trees, while those of the tropics can.
Unless this were the case those of the tropics could hardly

408
ever reach the light. In our temperate countries twiners
which die down every year would gain nothing as they could
not reach the summit in a single season. With most twining
plants all the branches, however many there may be, go on
revolving together; but, according to Mohl, the main stem
of Tamus elephantipes does not twine-only the branches.
On the other hand, with the asparagus, given in the table,
the leading shoot alone, and not the branches, revolved and
twined. Some produce shoots of two sorts, one of which
twines; the others not. In others the uppermost shoots
alone twine. One twines during the middle of the summer
but not in autumn. Some grow erect in dry South Africa,
their native country; but near Dublin, Ireland, they regularly twine.

Leaf Climbers. -The stems of several species of Clematis are twiners like the hop. But in addition to this mode
of holding fast, the petioles are sensitive to the touch,
slowly bend into the form of hooks, and if successful in
catching a stick they clasp it firmly and soon become greatly
enlarged and strengthened by an extra growth of woody
fibre. If they come in contact with no object they retain
this position for a considerable time, and then bending up-
wards they reassume their original upturned position, which
is retained ever afterwards. In Clematis calycina the
clasped petiole becomes nearly twice as thick as the leaf-
stalk which has clasped nothing. The petiole of the un-
clasped leaf is flexible, and can be easily snapped, whereas
the clasped footstalk acquires an extraordinary toughness
and rigidity so that considerable force is required to pull it
into pieces. The meaning of these changes is plain, namely,
that the petioles may firmly and durably support the stem.
In some species of Clematis furnished with compound leaves
the main petiole alone is sensitive, while some have two or
three sub-petioles, also sensitive; still others have the entire number, as many as seven, sensitive. Some petioles
are extremely sensitive to very light weights, as one-eighth

409
When a petiole clasps a stick it

of a grain. They will clasp thin withered blades of grass,
the soft young leaves of a maple, or the lateral flower pe-
duncles of the quaking grass Briza; the latter are only
about as thick as a hair from a man's beard, but they were
completely surrounded and clasped.

The first petiole of Tropæolum tricolorum var. grandiflorum bear no laminæ or blades, and are very sensitive to
touch, sometimes bending into a complete ring in six minutes. The next filaments above have their tips slightly
enlarged, and those still farther up the stem still more
enlarged ; so we find all grades, from tendrils to leaves with
large blades. All of these petioles are sensitive; those
without blades acting in every way like genuine tendrils;
the latter are short lived, however, dropping off as soon as
the petioles of the true leaves have clasped the support
above. The most remarkable fact, and which I have observed in no other species of the genus, is that the filaments
and petioles of the young leaves, if they catch no object,
after standing in their original position for some days, spontaneously and slowly move, oscillating a little from side to
side towards the stem of the plant. Hence all the petioles
and filaments, though arising on different sides of the axis,
ultimately bend towards and clasp either their own stem or
the supporting stick. The petioles and filaments often be-
come, after a time, in some degree contracted, presenting
features much like true tendrils.

Maurandia semperflorens (Scrophulariaceæ) has flower
peduncles which are sensitive like tendrils, and exhibit re-
volving powers. These spontaneous movements seem to be
of no service to the plant as they lose the power when the
flower is old enough to open. The leaf-stalks and internodes
of this plant do not twine.

Lophospermum scandens var. purpureum when young has
sensitive internodes.

draws the base of the internode against it; and then the
internode itself bends towards the stick, which is thus

410
caught between the stem and the petiole as by a pair of
pincers. The internode straightens itself again, excepting
the part in contact with the stick.

With Solanum jasminoides (Fig. 88) as in no other leaf-
climber examined, a leaf grown to its full size was capable
of clasping a stick ; but the movement was extremely slow,
requiring several weeks. On comparing a thin transverse
slice of this petiole with
one from the next or older
leaf beneath, which had not
clasped anything, its diameter was found to be fully
doubled, and its structure
greatly changed. In the
section of the petiole
which had during several
weeks clasped a stick, the
two upper ridges have become much less prominent,
and the two groups of
woody vessels beneath
them much increased in

Fig. 88.
Solanum jasminoides.

diameter. The semilunar band is converted into a complete
ring of very hard, white, woody tissue, with lines radiating
from the centre. The three groups of vessels, which, though
closely approximate, were before distinct, are now completely blended together. This clasped petiole had actually
become thicker than the stem close beneath; due chiefly to
the greater thickness of the ring of wood.

Plants belonging to eight families are known to have
clasping petioles, and plants belonging to four families climb
by the tips of their leaves. With rare exceptions the petioles are sensitive only whilst young; they are sensitive on
all sides, but in different degrees in different plants.

Tendril-bearing Plants. - By tendrils are meant filamentary organs, sensitive to contact and used exclusively

411
for climbing. They are formed by the modification of leaves
with their petioles, of flower-peduncles, perhaps also of
branches and stipules. The species of tendril bearers described belong to ten natural families. Species of Bignonia
and some others taken together, afford connecting links
between twiners, leaf-climbers, tendril-bearers, and root
climbers. Some little time after the stem of Bignonia
Tweedyana has twined round an upright stick, and is securely fastened to it by the clasping petioles and tendrils, it
emits at the base of its leaves aerial roots which curve partly
round and adhere to the stick; so that this one species of
Bignonia combines four different methods of climbing, generally characteristic of distinct plants, namely, twining, leaf-climbing, tendril-climbing, and root-climbing.

The movements of Bignonia venusta are quite complicated. Not only the tendrils but the petioles bearing them
revolve; these petioles, however, are not in the least sensitive. Thus the young internodes, the petioles, and the
tendrils, all at the same time, go on revolving together, but
at different rates. Moreover the movements of the opposite
petioles and tendrils are quite independent of each other.
One other curious point remains to be mentioned. In a few
days after the toes have closely clasped a stick, their blunt
extremities become, though not invariably, developed into
irregular disk-like balls, which have the singular power of
adhering firmly to the wood.

The simple undivided tendril of Bignonia speciosa ends in
an almost straight, sharp, uncolored point. The whole terminal part exhibits an odd habit, which in an animal would
be called an instinct; for it continually searches for any little
dark hole into which to insert itself. The tendrils slowly
travel over the surface of the wood, and when the apex came
to a hole or a fissure it inserted itself, often bending at right
angles to the basal part. The same tendril would frequently
withdraw from one hole and insert its point into a second
one. Mr. Darwin says: "Improbable as this view may be

412
I am led to suspect that this habit in the tendril of inserting
its tip into dark holes and crevices has been inherited by the
plant after having lost the power of forming adhesive disks."

A plant of Bignonia capreolata was several times shifted
in position in a box where one side only was exposed to the
light; in two days all six tendrils pointed with unerring
truth to the darkest corner of the box, though to do this
each had to bend in a different manner. Six tattered flags
could not have pointed more truly from the wind than did
these branched tendrils from the stream of light which entered the box. When a tendril does not succeed in clasping
a support it bends downwards and then towards its own
stem, which it seizes, together with the supporting stick, if
there be one. If the tendril seizes nothing it does not contract, spirally, but soon withers away and drops off. A
bunch of wool was placed in the way of the tendrils; they
caught one or two fibres and then the tips began to swell
into irregular balls above the one-twentieth of an inch in
diameter. The surfaces of these balls secrete some viscid
resinous matter, to which the fibres of the wool adhere, so
that after a time fifty or sixty fibres are all deeply imbedded
in one ball of tendril. These tendrils quite fail to attach
themselves to a brick wall. These plants are especially
adapted to climb trees clothed with lichens and mosses which
abound on the trees in the native country of the Bignonia.

Cobæa scandens (Polemoniacec) is an admirable climber.
The terminal portion of the petiole which forms the tendril
is sometimes eleven inches long. The tendril performs one
revolution against the sun in an hour and a quarter. The
base of the petiole and the internodes do not move at all.

A large majority of the tendrils of Corydalis claviculata
still bear leaflets, though excessively reduced in size. We
here behold a plant in an actual state of transition from a
leaf-climber to a tendril-bearer. Whilst the plant is young,
only the outer leaves, but when full-grown all the leaves,
have their extremities more or less perfectly converted into
tendrils.

413
Echinocystis lobata. 
A thin, smooth, cylindrical, stick
was placed so far from a tendril that its extremity could
only curl half or three-quarters round the stick. It was
always found in the course of a few hours afterwards that
the tip had managed to curl twice or even thrice quite round
the stick. Measurements showed that this was not due to
the growth of the tendril. Whilst the tendril was slowly
and quite insensibly crawling onwards it was observed that
the whole surface was not in close contact with the stick.
The onward movement is supposed to be slightly vermicular,
or that the tip alternately straightens itself a little and then
again curls inwards, thus dragging itself onwards by an in-
sensibly slow, alternate movement, which may be compared
to that of a strong man suspended by the ends of his fingers
to a horizontal pole, who works his fingers onwards until he
can grasp the pole with the palm of his hand. Experiments
upon this interesting plant were made and the results published by Dr. Asa Gray, in 1858. This led Mr. Darwin to
more extended observations upon many other climbing
plants. He is only one of a large number of persons who
are indebted for valuable hints from the sagacious botanist
of Cambridge, Mass.

Hanburya Mexicana. In a few days after the tips of the
tendrils have grasped an object the inferior surface swells
and becomes developed into a cellular layer, which adapts
itself closely to the wood, and firmly adheres to it. This is
not the extreme tip of the tendril but a trifle back of it.
This layer apparently secretes some resinous cement, as it is
not loosened by water or alcohol, but is freed by the action
of ether and turpentine.

Tendrils of plants belonging to Vitacec, Sapindaceæ,
Passifloracec, and perhaps others, are modified flower peduncles, but their homological nature makes no difference in
their action. Figure 89 shows part of the tendril of a grapevine bearing flowers. From this state we can trace every
stage till we come to a full-sized common tendril, bearing on

414
the branch which corresponds with the sub-peduncle one
single flower-bud!

Ampelopsis quinquefolia (Fig. 90), tendril, with the young leaf. 
Fig. 91, tendril, several weeks after its attachment to
a wall, with the branches thickened and spirally contracted,
and with the extremities developed into
disks. The unattached
branches have withered and dropped off.)
climbs by tendrils like
the grape-vine, but in
addition has a way of
holding fast to plain
surfaces by means of
little disks or cushions. These disks are
apparently never developed without a con-
tact with some object.
A tendril which has
not become attached
to any body does not
contract spirally ; and
in course of a week or
two shrinks into the

Fig. 89.
Grape-vine.

finest thread, withers and drops off. An attached tendril, on
the other hand, contracts spirally, and thus becomes highly
elastic ; so that when the main foot-stalk is pulled, the strain
is equally distributed to all the attached disks. During the
following winter it ceases to live but remains firmly attached
to the stem and to the surface of attachment. The gain in
strength and durability in a tendril after its attachment is
something wonderful. They adhere still strong after an
exposure to the weather for fourteen or fifteen years. One
single lateral branchlet of a tendril, estimated to be at least

415
ten years old, was still elastic and supported a weight of
exactly two pounds. This tendril had five disk-bearing
branches of equal thickness and of apparently equal strength,
so that this one tendril, after having been exposed during
ten years to the weather, would have resisted a strain of ten
pounds!

Spiral Contractions .- Tendrils of many kinds of plants
if they catch nothing, contract after an interval of several

Fig. 90.
Woodbine.

days or weeks into a close spire. A few contract into a
helix.
The spiral contraction which ensues after a tendril has
caught a support is of high service to all tendril-bearing
plants; hence its almost universal occurrence with plants of
widely different orders. When caught the spiral contraction drags up the shoot. Thus there is no waste of growth,
and the stretched stem ascends by the shortest course. A
far more important service rendered by the spiral contraction
is that the tendrils are thus made highly elastic. The strain,
as in Ampelopsis, is thus equally distributed to the several
attached branches of a branched tendril. It is this elasticity
which saves both branched and simple tendrils from being
torn away during stormy weather. In
In one case observed

416
Fig. 91.

Woodbine.

the Bryony (Fig. 92) safely rode out the gale, like a ship
with two anchors down, and with a long range of cable
ahead to serve as a spring as she surges to the storm. When
an uncaught tendril contracts spirally the spire always runs
in the same direction from tip to base. A tendril, on the
other hand, which has caught a support by its extremity,
invariably becomes twisted in one part in one direction, and
in another part in the opposite direction; the oppositely
turned spires being separated by short, straight portions.
Sometimes the
spires of a tendril alternately
turn as many as
five times in opposite directions,
with straight
portions between
them; even seven
or eight have
been seen by M.
Léon. Whether
few spires, or
many, there are
as many in one
direction as in
the other. To give an illustration; when a haberdasher
winds up ribbon for a customer he does not wind it into a
single coil ; for. if he did, the ribbon would twist itself as
many times as there were coils; but he winds it into a figure
of eight on his thumb and little finger, so that he alternately
takes turns in opposite directions, and thus the ribbon is not
twisted. So it is with tendrils, with this sole difference,
that they take several consecutive turns in one direction, and
then the same number in an opposite direction ; but in both
cases the self-twisting is equally avoided. Passiflora gracilis
has the most sensitive tendrils which were seen; a bit of

417
platina wire, one-fiftieth of a grain in weight, gently placed
on the concave point, caused two tendrils to become hooked.
After a touch the tendril began to move in twenty-five seconds. Dr. Asa Gray saw tendrils of Sicyos move in thirty
seconds. Other tendrils move in a few minutes; in the.
Dicentra in half an hour; in the Smilax in an hour and a
quarter; and in the Ampelopsis still more slowly. Tendrils
move to the touch of almost any substance, drops of water
excepted. Adjoining tendrils rarely catch each other. Some
tendrils have their revolving motion accelerated and retarded
in moving to and from the light; others are indifferent to its
action. America which so abounds with arboreal animals

Fig. 92.
Bryony.

abounds with climbing plants; and, of the tendril-bearing
plants examined the most admirably constructed come from
this grand continent, namely, the several species of Bignonia, Eccremocarpus, Cobœa, and Ampelopsis.

Root Climbers .- Ficus repens climbs up walls just like
ivy ; when the young rootlets were made to press lightly on
slips of glass they emitted, after about a week's interval,
minute drops of clear fluid, slightly viscid. One small drop
the size of half a pin's head, was mixed with grains of sand.
The slip of glass was left exposed in a drawer during hot
and dry weather. The mass remained fluid during one hundred and twenty-eight days; how much longer was not observed. The rootlets seem to first secrete a slightly viscid

418
fluid and then absorb the watery plants, and ultimately leave
a cement.

Plants become climbers, in order, it may be presumed, to
reach the light, and to expose a large surface of leaves to its
action and to that of the free air. This is effected by climbers
with wonderfully little expenditure of organized matter, in
comparison with trees, which have to support a load of heavy
branches by a massive trunk. Because these climbing plants
graduate into each other they have " become" climbers by
gradual changes. This looks too much like the old fanciful
theory that has again and again appeared, namely, the giraffe
acquired his long neck by a constant desire for high twigs,
and an effort to reach them; the elephant his long trunk by
a similar desire and effort to reach the grass at his feet. We
cannot see how homology indicates descent. We do not believe because the various modes of inflorescence run into each
other (homologous) that they have all been derived from one
common form. Mr. Darwin believes that leaf-climbers were
primordially twiners, and tendril-bearers were primordially
leaf-climbers ; and thinks he understands how the change has
been brought about; yet he says "if we inquire how the
petiole of a leaf, or the peduncle of a flower, or a branch,
first becomes sensitive and acquires the power of bending
towards the touched side, we get no certain answer." We
are again silenced if we inquire how the stems, petioles,
tendrils, and flower peduncles first acquired their power of
spontaneously revolving. Below we give a good sample of
Darwinism.

"If these views be correct Lathyrus nissolia must be descended from a primordial spirally-twining plant; that this
became a leaf-climber; that first, part of the leaf, and then
the whole leaf became converted into a tendril, with the
stipules by compensation greatly increased in size; that this
tendril lost its branches and became simple, then lost its revolving-power (in which state it would resemble the tendril
of the existing L. aphaca), and afterwards losing its prehensile

419
power and becoming foliacious, would no longer
be called a tendril. In this last stage (that of the existing
L. nissolia), the former tendril would reassume its original
function of a leaf, and its lately largely developed stipules
being no longer wanted would decrease in size." He believes that the capacity of acquiring the revolving power on
which most climbers depend is inherent, though undeveloped, in almost every plant in the vegetable kingdom.
Notwithstanding his peculiar views, which are so enticing to
many, we must acknowledge that he is a shrewd and accurate
observer, and that in this paper, as in many others, he has
patiently collected a vast amount of valuable information
upon a great variety of subjects.