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THE

MOVEMENTS AND HABITS

OF

CLIMBING PLANTS.

BY THE SAME AUTHOR,

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MOVEMENTS AND HABITS

CLIMBING PLANTS.

oe

By CHARLES DARWIN, MA, FBS, ~

ETO.

C

SECOND EDITION, REVISED.

WITH ILLUSTRATIONS.

NEW YORK:
D. APPLETON AND COMPANY,

I, 3, AND 5 BOND STREET.

1884.
i>

P3..
yey

PREFACE.

+

Tus Essay first appeared in the ninth volume of
the ‘Journal of the Linnean Society,’ published in
1865. It is here reproduced in a corrected and, I
hope, clearer form, with some additional facts. The
illustrations were drawn by my son, George Darwin.
Fritz Miller, after the publication of my paper, sent
to the Linnean Society (Journal, vol. ix., p. 344) some
interesting observations on the climbing plants of
South Brazil, to which I shall frequently refer.
Recently two important memoirs, chiefly on the
difference in growth between the upper and lower
sides of tendrils, and on the mechanism of the move-
ments of twining plants, by Dr. Hugo de Vries, have
appeared in the ‘ Arbeiten des Botanischen Instituts
in Wiirzburg,’ Heft. iii, 1873. These memoirs ought
to be carefully studied by every one interested in the
subject, as I can here give only references to the

more important points. This excellent observer, as

vi PREFACE.

well as Professor Sachs,” attributes all the movements
of tendrils to rapid growth along one side; but, from
reasons assigned towards the close of my fourth
chapter, I cannot persuade myself that this holds
good with respect to those due to a touch. In order
that the reader may know what points have interested
me most, I may call his attention to certain tendril-
bearing plants; for instance, Bignonia capreolata,
Cobea, Echinocystis, and Hanburya, which display
as beautiful adaptations as can be found in any part
of the kingdom of nature. It is, also, an interesting
fact that intermediate states between organs fitted for
widely different functions, may be observed on the
same individual plant of Corydalis claviculata and
the common vine; and these cases illustrate In a
striking manner the principle of the gradual evolu-

tion of species.

* An English translation of of ‘Text-Book of Botany,’ and this
the ‘Lehrbuch der Botanik’ by is a great boon to all lovers of
Professor Sachs, has recently natural science in England.
(1875), appeared under the title

CONTENTS.

—1oe

CHAPTER I.
Twinine Puants.

Introductory remarks—Description of the twining of the Hop
—Torsion of the stems—Nature of the revolving movement
and manner of ascent—Stems not irritable—Rate of revolu-
tion in various plants — Thickness of the support round
which plants can twine—Species which revolve in an anoma-
lous manner «wwe wet wees Pages 1-44

CHAPTER II.
LEar-CLIMBERS.

Plants which climb by the aid of spontaneously revolving and
sensitive petioles— Clematis—Tropeolum—Maurandia, flower-
peduncles moving spontaneously and sensitive to a touch—
Rhodochiton—L ophospermum, internodes sensitive—Solunum,
thickening of the clasped petioles — Fumaria ~— Adlumia—
Plants which climb by the aid of their produced midribs—
Gloriosa —- Flagellaria — Nepenthes — Summary on _leaf-
climbers ..0 6. ++ ve ew we tee ewe 45-83

CHAPTER III.
TENDRIL-BEARERS.

Nature of tendrils—BicNonIACcEx, various species of, and their
different modes of climbing—Tendrils which avoid the light,
and creep into crevices—Development of adhesive discs—
Excellent adaptations for seizing different kinds of supports
— PoLEMONIACEE — Cobea scandens, much branched and

viii CONTENTS.

hooked tendrils, their manner of action — LEGUMINOSZ —
Composirz — SmILacrz — Smilax aspera, its inefficient
tendrils — Fumanracem — Corydalis claviculata, its state
intermediate between that of a leaf-climber and a tendril-
BORER nen ake SB ge oe BE Sede Ms Pages 84-126

CHAPTER IV.
TENDRIL-BEARERS—continued.

CuourniTacEx — Homologous nature of the tendrils—Zchino-
cystis lobata, remarkable movements of the tendrils to avoid
seizing the terminal shoot—Tendrils not excited by contact
with other tendrils or by drops of water—Undulatory move-
ment of the extremity of the tendril—Hanburya, adherent
discs — Vitacex —Gradation between the flower-peduncles
and tendrils of the vine—Tendrils of the Virginian Creeper
turn from the light, and after contact develop adhesive
discs —SaPINDACEZ—PassiIFLORACERZ—Passiflora gracilis —
Rapid revolving movement and sensitiveness of the tendrils
—Not sensitive to the contact of other tendrils or of drops of
water — Spiral contraction of tendrils — Summary on the
nature and action of tendrils .. .. « . +. 127-182

CHAPTER V.
Hook AND Root-Crimsers.—ConoLupIne REMARKS.

Plants climbing by the aid of hooks, or merely scrambling over
other plants—Root-climbers, adhesive matter secreted by the
rootlets—General conclusions with respect to climbing plants,
and the stages of their development .. .. .. 183-206

INDEK: 46: os ae ewe wwe sae 207

THE

MOVEMENTS AND HABITS

OF

CLIMBING PLANTS.

CHAPTER I.

Twinine PLants,

Tatroductory remarks—Description of the twining of the Hop—Torsion
of the stems—Nature of the revolving movement, and manner of
ascent—Stems not irritable—Rate of revolution in various plants—
Thickness cf the support round which plants can twine—Species
which revolve in an anomalous manner.

I was led to this subject by an interesting, but short

paper by Professor Asa Gray on the movements of the

tendrils of some Cucurbitaceous plants.* My obser-
vations were more than half completed before I learnt
that the surprising phenomenon of the spontaneous
revolutions of the stems and tendrils of climbing
plants had been long ago observed by Palm and by

Hugo von Mohl,t and had subsequently been the

subject of two memoirs by Dutrochet.t Nevertheless,

* ‘Proc, Amer. Acad. of Arts pflanzen,’ 1827. Palm’s Treatise

and Sciences, vol. iv. Aug. 12,
1858, p. 98.

t Ludwig H. Palm, ‘ Ueber das
Winden der Pflanzen ;’ Hugo von
Mohl, ‘ Ueber den Bau und das
Wiuden der Ranken und Schling-

was published only a few weeks
before Mohl’s. See also ‘The Ve-
getable Cell’ (translated by Hen-
frey), by H. von Mohl, p. 147 to
end,

t¢ “Des Mouvements révolutifs

2 TWINING PLANTS. Cuap. I

I believe that my observations, founded on the ex-
amination of above a hundred widely distinct living
species, contain sufficient novelty to justify me in
publishing them.

Climbing plants may be divided into four classes.
First, those which twine spirally round a support, and
are not aided by any other movement. Secondly,
those endowed with irritable organs, which when they
touch any object clasp it; such organs consisting of
modified leaves, branches, or flower-peduncles. But
these two classes sometimes graduate to a certain
extent into one another. Plants of the third class
ascend merely by the. aid of hooks; and those of the
fourth by rootlets; but as in neither class do the plants
exhibit any special movements, they present little
interest, and generally when I speak of climbing plants
I refer to the two first great classes.

TWINING PLANTS.

This is the largest subdivision, and is apparently
the primordial and simplest condition of the class.
My observations will be best given by taking a few
special cases. When the shoot of-a Hop (Humulus
lupulus) rises from the ground, the two or three first-
formed joints or internodes are straight and remain
stationary; but the next-formed, whilst very young,

spontanés,” &c.,‘ComptesRendus, cherches sur la Volubilité des
tom. xvii. (1843) p. 989; “Re- Tiges,” &c., tom. xix.(1844) p. 295.

Ouap. L. TWINING PLANTS. 3

may be seen to bend to one side and to travel slowly
round towards all points of the compass, moving, like
the hands of a watch, with the sun. The movement
very soon acquires its full ordinary velocity. From
seven observations made during August on shoots pro-
ceeding from a plant which had been cut down, and on
another plant during April, the average rate during hot
weather and during the day is 2 hrs. 8 m. for each revo-
lution; and none of the revolutions varied much from
this rate. The revolving movement continues as long
as the plant continues to grow; but each separate
internode, as it becomes old, ceases to move.

To ascertain more precisely what amount of move-
ment each internode underwent, I kept a potted plant,
during the night and day, in a well-warmed room to
which I was confined by illness. A long shoot pro-
jected beyond the upper end of the supporting stick,
and was steadily revolving. I then took a longer stick
and tied up the shoot, so that only a very young inter-
node, 12 of an inch in length, was left free. This was so
nearly upright that its revolution could not be easily
observed ; but it certainly moved, and the side of the
internode which was at one time convex became concave,
which, as we shall hereafter see, is a sure sign of the
revolving movement. I will assume that it made at
least one revolution during the first twenty-four hours.
Early the next morning its position was marked, and it
made a second revolution in 9 hrs.; during the latter
part of this revolution it moved much quicker, and the
third circle was performed in the evening in a little over

4 TWINING PLANTS. Cuar. L

3hrs. As on the succeeding morning I found that the
shoot revolved in 2 hrs. 45 m., it must have made during
the night four revolutions, each at the average rate of
a little over 3hrs. I should add that the temperature
of the room varied only a little. The shoot had now
grown 34 inches in length, and carried at its extremity
a young internode 1 inch in length, which showed
slight changes in its curvature. The next or ninth
revolution was effected in 2hrs. 30m. From this time
forward, the revolutions were easily observed.. The
thirty-sixth revolution was performed at the usual
rate; so was the last or thirty-seventh, but it was not
completed ; for the internode suddenly became upright,
and after moving to the centre, remained motionless.
I tied a weight to its upper end, so as to bow it slightly
and thus detect any movement; but there was none.
Some time before the last revolution was half performed,
the lower part of the internode ceased to move.

A few more remarks will complete all that need be
said about this internode. It moved during five
days; but the more rapid movements, after the per-
formance of the third revolution, lasted during three
days and twenty hours. The regular revolutions,
from the ninth to thirty-sixth inclusive, were effected
at the average rate of 2 hrs. 31m.; but the weather was
cold, and this affected the temperature of the room,
especially during the night, and consequently retarded
the rate of movement a little. There was only one
irregular movement, which consisted in the stem rapidly
making, after an unusually slow revolution, only the

Cuar. I. TWINING PLANTS. 5

segment ofa circle. After the seventeenth revolution
the internode had grown from 13 to 6 inches in length,
and carried an internode 1% inch long, which was
just perceptibly moving ; and this carried a very minute
ultimate internode. After the twenty-first revolution,
the penultimate internode was 2} inches long, and
probably revolved in a period of about three hours.
At the twenty-seventh revolution the lower and still
moving internode was 83, the penultimate 3}, and
the ultimate 24 inches in length; and the inclination
of the whole shoot was such, that a circle 19 inches
in diameter was swept by it. When the movement
ceased, the lower internode was 9 inches, and the
penultimate 6 inches in length; so that, from the
twenty-seventh to thirty-seventh revolutions inclusive,
three internodes were at the same time revolving.

The lower internode, when it ceased revolving,
became upright and rigid; but as the whole shoot
was left to grow unsupported, it became after a time
bent into a nearly horizontal position, the uppermost
and growing internodes still revolving at the extremity,
but of course no longer round the old central point of
the supporting stick. From the changed position
of the centre of gravity of the extremity, as it revolved,
a slight and slow swaying movement was given to the
long horizontally projecting shoot; and this movement
I at first thought was a spontaneous one. As the shoot
grew, it hung down more and more, whilst the growing
and revolving extremity turned itself up more and more.

With the Hop we have seen that three internodes

6 TWINING PLANTS, Caav. L

were at the same time revolving ; and this was the case
with most of the plants observed by me. With all, if in
full health, two internodes revolved; so that by the time
the lower one ceased to revolve, the one above was in
full action, with a terminal internode just commencing
to move. With Hoya carnosa,on the other hand, a
depending shoot, without any developed leaves, 32
inches in length, and consisting of seven internodes
(a minute terminal one, an inch in length, being
counted), continually, but slowly, swayed from side
to side in a semicircular course, with the extreme
internodes making complete revolutions. This sway-
ing movement was certainly due to the movement of
the lower internodes, which, however, had not force
sufficient to swing the whole shoot round the central
supporting stick. The case of another Asclepiadaceous
plant, viz., Ceropegia Gardnerit, is worth briefly giving.
I allowed the top to grow out almost horizontally to
the length of 31 inches; this now consisted of three
long internodes, terminated by two short ones. The
whole revolved in a course opposed to the sun (the
reverse of that of the Hop), at rates between 5 hrs. 15 m.
and 6 hrs. 45m. for each revolution. The extreme tip
thus made a circle of above 5 feet (or 62 inches) in dia-
meter and 16 feet in circumference, travelling at the
rate of 32 or 33 inches per hour. The weather being
hot, the plant was allowed to stand on my study-table ;
and it was an interesting spectacle to watch the loug
shoot sweeping this grand cricle, night and day, in
search of some object round which to twine.

Cuar. I. TWINING PLANTS. 7

If we take hold of a growing sapling, we can of
course bend it to all sides in succession, so as to make
the tip describe a circle, like that performed by the
summit of a spontaneously revolving plant. By this
movement the sapling is not in the least twisted
round its own axis. I mention this because if a black
point be painted on the bark, on the side which is
uppermost when the sapling is bent towards the
holder’s body, as the circle is described, the black
point gradually turns round and sinks to the lower
side, and comes up again when the circle is completed ;
and'this gives the false appearance of twisting, which,
in the case of spontaneously revolving plants, deceived
me for atime. The appearance is the more deceitful
because the axes of-nearly all twining-plants are
really twisted; and they are twisted in the same
direction with the spontaneous revolving movement.
To give an instance, the internode of the Hop of
which the history has been recorded, was at first, as
could be seen by the ridges on its surface, not in the
least twisted ; but when, after the 37th revolution, it
had grown 9 inches long, and its revolving movement
had ceased, it had become twisted three times round
its own axis, in the line of the course of the sun; on
the other hand, the common Convolvulus, which
revolves in an opposite course to the Hop, becomes
twisted in an opposite direction.

Hence it is not surprising that Hugo von Mohl
(p. 105, 108, &c.) thought that the twisting of the
axis caused the revolving movement; but it is not

8 TWINING PLANTS. Cuap. 1

possible that the twisting of the axis of the Hop three
times should have caused thirty-seven revolutions.
Moreover, the revolving movement commenced in the
young internode before any twisting of its axis could
be detected. The internodes of a young Siphomeris
and Lecontea revolved during several days, but became
twisted only once round their own axes. The best
evidence, however, that the twisting does not cause the
revolving movement is afforded by many leaf-climbing
and tendril-bearing plants (as Pisum sativum, Echino-
cystis lobata, Bignonia capreolata, Eecremocarpus scaber,
and with the leaf-climbers, Solanum jasminoides ‘and
various species of Clematis), of which the internodes are
not twisted, but which, as we shall hereafter see, re-
gularly perform revolving movements like those of true
twining-plants. Moreover, according to Palm (pp. 30,
95) and Mohl (p. 149), and Léon,* internodes may
occasionally, and even not very rarely, be found which
are twisted in an opposite direction to the other inter-
nodes on the same plant, and to the course of their
revolutions ; and this, according to Léon (p. 356), is
the case with all the internodes of a certain variety of
Phaseolus multijlorus. Internodes which have become
twisted round their own axes, if they have not ceased
to revolve, are still capable of twining round a support,
as I have several times observed.

Mohl has remarked (p. 111) that when a stem twines
round a smooth cylindrical stick, it does not become

* ‘Bull. Bet. Soc. de France,’ tom. v. 1858, p. 356,

Cuap. L TWINING PLANTS. 9

twisted.* Accordingly I allowed kidney-beans to run
up stretched string, and up smooth rods of iron and
glass, one-third of an inch in diameter, and they
became twisted only in that degree which follows as a
mechanical necessity from the spiral winding. The
stems, on the other hand, which had ascended ordinary
rough sticks were all more or less and generally much
twisted. The influence of the roughness of the support
in causing axial twisting was well seen in the stems
which had twined up the glass rods; for these rods
were fixed into split sticks below, and were secured
above to cross sticks, and the stems in passing these
places became much twisted. As soon as the stems
which had ascended the iron rods reached the summit
and became free, they also became twisted; and this
apparently occurred more quickly during windy than
during calm weather. Several other facts could be given,
showing that the axial twisting stands in some relation
to inequalities in the support, and likewise to the shoot
revolving freely without any support. Many plants,
which are not twiners, become in some degree twisted
round their own axes; f but this occurs so much more

* This whole subject has been
ably discussed and explained by
H. de Vries, ‘Arbeiten des Bot.
Instituts in Wiirzburg,’ Heft iii.
pp. 331, 336. Seealso Sachs (‘ Text-
Bovk of Botany,’ English transla-
tion, 1875, p. 7705, who concludes
“ that torsion is the result of growth
continuing in the outer layers after

it has ceased or begun to cease in
the inner layers.”

¢ Professor Asa Gray has re-
marked to me, in a letter, that in
Thuja occidentalis the twisting of
the bark is very conspicuous. The
twist is generally to the right of
the observer; but, in noticing
about a hundred trunks, four or

Cuap. L

10 TWINING PLANTS.

generally and strongly with twining-plants than with
other plants, that there must ‘be some connexion
between the capacity for twining and axial twisting.
The stem probably gains rigidity by being twisted
(on the same principle that a much twisted rope is
stiffer than a slackly twisted one), and is thus in-
directly benefited so as to be enabled to pass over
inequalities in its’ spiral ascent, and to carry its own
weight when allowed to revolve freely.*

I have alluded to the twisting which necessarily
follows on mechanical principles from the spiral
ascent of a stem, namely, one twist for each spire
completed. This was well shown by painting straight
lines on living stems, and then ailowing them to twine ;
but, as I shall have to recur to this subject under
Tendrils, it may be here passed over.

The revolving movement of a twining plant has
been compared with that of the tip of a sapling, moved
round and round by the hand held some way down
the stem; but there is one important difference.
The upper part of the sapling when thus moved

five were observed to be twisted
in an opposite direction. The
Spanish chestnut is often much
twisted: there is an interesting
article on this subject in the
‘Scottish Farmer,’ 1865, p. 833.

* It is well known that the
stems of many plants occasionally
become spirally twisted in a
monstrous manner; and after my
paper was read before the Linnean
Society. Dr. Maxwell Masters re-

marked to me in a letter that
“some of these cases, if not all,
are dependent upon some obstacle
or resistance to their upward
growth.” This conclusion agrees
with what I have said about the
twisting of stems, which have
twined round rugged supports;
but does not preclude the twist-
ing being of service to the plant
by giving greater rigidity to the
stem.

Cua. I. TWINING PLANTS. 11

remains straight; but with twining plants every part
of the revolving shoot has its own separate and
independent movement. This is easily proved; for
when the lower half or two-thirds of a long revolving
shoot is tied to a stick, the upper free part continues
steadily revolving. Even if the whole shoot, except
an inch or two of the extremity, be tied up, this part,
as I have seen in the case of the Hop, Ceropegia,
Convolvulus, &c., goes on revolving, but much more
slowly ; for the internodes, until they have grown to
some little length, always move ‘slowly. If we look to
the one, two, or several internodes of a revolving shoot,
they will be all seen to be more or less bowed, either
during the whole or during a large part of each revolu-
tion. Now if acoloured streak be painted (this was
done with a large number of twining plants) along,
we will say, the convex surface, the streak will after
a time (depending on the rate of revolution) be
found to be running laterally along one side of the
bow, then along the concave side, then laterally on
the opposite side, and, lastly, again on the originally
convex surface. This clearly proves that during the
revolving movement the internodes become bowed
in every direction. The movement is, in fact, a con-
tinuous self-bowing of the whole shoot, successively
directed to all points of the compass; and has been
well designated by Sachs as a revolving nutation.

As this movement is rather difficult to understand,
it will be well to give an illustration. Take a sapling
and bend it to the south, and paint a black line on the

12 TWINING PLANTS. Cuap. I.

convex surface ; let the sapling spring up and bend it
to the east, and the black line will be seen to run
along the lateral face fronting the north; bend it to
the north, the black line will be on the concave
surface ; bend it to the west, the line will again be on
the lateral face; and when again bent to the south,
the line will be on the original convex surface. Now,
instead of bending the sapling, let us suppose that the
cells along its northern surface from the base to the
tip were to grow much more rapidly than on the three
other sides, the whole shoot would then necessarily be
bowed tothe south; and let the longitudinal growing
surface creep round the shoot, deserting by slow degrees
the northern side and encroaching on the western side,
and so round by the south, by the east, again to the
north. In this case the shoot would remain always
bowed with the painted line appearing on the several
above specified surfaces, and with the point of the
shoot successively directed to each point of the
compass. In fact, we should have the exact kind of
movement performed by the revolving shoots of twining
plants.*

It must not be supposed that the revolving move-
ment is as regular as that given in the above illustra-
tion ; in very many cases the tip describes an ellipse,
even a very narrow ellipse. To recur once again to

* The view that the revolving H.de Vries; and the truth of this
movement or nutation of the stems view is proved by their excellent
of twining plants is due to growth cbservations.
is that advanced by Sachs and

Cuar. I. TWINING PLANTS. 13

our illustration, if we suppose only the northern and
southern surfaces of the sapling alternately to grow
rapidly, the summit would describe a simple arc; if
the growth first travelled a very little to the western
face, and during the return a very little to the eastern
face, a narrow ellipse would be described; and the
sapling would be straight as it passed to and fro
through the intermediate space; and a complete
straightening of the shoot may often be observed in
revolving plants. The movement is frequently such
that three of the sides of the shoot seem to be growing
in due order more rapidly than the remaining side; so
that a semi-circle instead of a circle is described, the
shoot becoming straight and upright during half of its
course.

When a revolving shoot consists of several inter-
nodes, the lower ones bend together at the same rate,
but one or two of the terminal ones bend at a slower
rate; hence, though at times all the internodes are
in the-same direction, at other times the shoot is
rendered slightly serpentine. The rate of revolution
of the whole shoot, if judged by the movement of the
extreme tip, is thus at times accelerated or retarded.
One other point must be noticed. Authors have ob-
served that the end of the shoot in many twining plants
is completely hooked ; this is very general, for instance,
with the Asclepiadacee. The hooked tip, in all the
cases observed by me, viz. in Ceropegia, Spherostema,
Clerodendron, Wistaria, Stephania, Akebia, and Sipho-
meris, has exactly the same kind of movement as the

14 TWINING PLANTS. Cuar. L

other internodes; for a line painted on the convex
surface first becomes lateral and then concave; but,
owing to the youth of these terminal internodes, the
reversal of the hook is a slower process than that of the
revolving movement.* This strongly marked tendency
in the young, terminal and flexible internodes, to bend
in a greater degree or more abruptly than the other
internodes, is of service to the plant ; for not only does
the hook thus formed sometimes serve to catch a
support, but (and this seems to be much more impor-
tant) it causes the extremity of the shoot to embrace
the support much more closely than it could otherwise
have done, and thus aids in preventing the stem from
being blown away during windy weather, as I have
many times observed. In Lonicera brachypoda the
hook only straightens itself periodically, and never
becomes reversed. I will not assert that the tips of
all twining plants when hooked, either reverse them-
selves or become periodically straight, in the manner
just described ; for the hooked form may in some cases
be permanent, and be due to the manner of growth of
the species, as with the tips of the shoots of the com-
mon vine, and more plainly with those of Cissus dis-
color—plants which are not spiral twiners.

The first purpose of the spontaneous revolving
movement, or, more strictly speaking, of the con-

* The mechanism by which the H. de Vries (ibid. p. 337): he
end of the shoot remains hooked concludes that ‘it depends on the
appears to be a difficult and __ relation between the rapidity of tor-
complex problem, discussed by Dr. sion and the rapidity of putation’

Cuar. I. TWINING PLANTS. 15

tinuous bowing movement directed successively to all
points of the compass, is, as Mohl has remarked, to
favour the shoot finding a support. This is admirably
effected by the revolutions carried on night and day,
a wider and wider circle being swept as the shoot
increases in length. This movement likewise explains
how the plants twine; for when a revolving shoot
meets with a support, its motion is necessarily arrested
at the point of contact, but the free projecting part
goes on revolving. As this continues, higher and
higher points are brought into contact with the
support and are arrested; and so onwards to the ex-
tremity; and thus the shoot winds round its support.
When the shoot follows the sun in its revolving
course, it winds round the support from right to left,
the support being supposed to stand in front of the
beholder; when the shoot revolves in an opposite
direction, the line of winding is reversed. As each
internode loses from age its power of revolving, it like-
wise loses its power of spirally twining. If a man
swings a rope round his head, and the end hits a stick,
it will coil round the stick according to the direction
of the swinging movement ; so it is with a twining plant,
a line of growth travelling round the free part of the
shoot causing it to bend towards the opposite side, and
this replaces the momentum of the free end of the rope.

All the authors, except Palm and Mohl, who have
discussed the spiral twining of plants, maintain that
such plants have a natural tendency to grow spirally.
Mohl believes (p. 112) that twining stems have

16 TWINING PLANTS. Cuar. 1

a dull kind of irritability, so that they bend towards
any object which they touch; but this is denied
by Palm. Even before reading Mohl’s interesting
treatise, this view seemed to me so probable that I
tested it in every'way that I could, but always with
anegative result. I rubbed many shoots much harder
than is necessary to excite movement'in any tendril
or in the foot-stalk of any leaf climber, but without any
effect. I then tied a light forked twig to a shoot of a
Hop, a Coropegia, Sphwrostema, and Adhatoda, so that
the fork pressed on one side alone of the shoot and
revolved with it; I purposely selected some very slow
revolvers, as it seemed most likely that these would
profit most from possessing irritability ; but in no case
was any effect produced.* Moreover, when a shoot
winds round a support, the winding movement is
always slower, as we shall immediately see, than
whilst it revolves freely and touches nothing. Hence
I conclude that twining stems are not irritable; and
indeed it is not probable that they should be so, as
nature always economizes her means, and irritability
would have been superfluous. Nevertheless I do not
wish to assert that they are never irritable; for the
growing axis of the leaf-climbing, but not spirally
twining, Lophospermum scandens is, certainly irritable;
but this case gives me confidence that ordinary twiners

* Dr. H. de Vries also has plants are not irritable, and that
shown (ibid. p. 321 and 325) bya the'cause of their winding up a
better method than that employed support is exactly what I have de-
by me, that the stems of twining scribed.

Cuar. L TWINING PLANTS. 17

do not possess any such quality, for directly after
putting a stick to the Lophospermum, I saw that it
behaved differently from a true twiner or any other
leaf-climber.*

The belief that twiners have a natural tendency to
grow spirally, probably arose from their assuming a
spiral form when wound round a support, and from the
extremity, even whilst remaining free, sometimes
assuming this form. The free internodes of vigor-
ously growing plants, when they cease to revolve,
become straight, and show no tendency to be spiral ;
but when a shoot has nearly ceased to grow, or when
the plant is unhealthy, the extremity does occasionally
become spiral. I have seen this in a remarkable
manner with the ends of the shoots of the Stauntonia and
of the allied Akebia, which became wound up into a close
spire, just like a tendril ; and this was apt to occur after
some small, ill-formed leaves had perished. The ex-
planation, I believe, is, that in such cases the lower parts
of the terminal internodes very gradually and suc-
cessively lose their power of movement, whilst the
portions just above move onwards and in their turn
become motionless; and this ends in forming an
irregular spire.

When a revolving shoot strikes a stick, it winds
round it rather more slowly than it revolves. For
instance, a shoot of the Ceropegia, revolved in 6 hrs.,

+ Dr. H. de Vries states (ibid. p. 822) that the stem of Cuscuta is
irritable like a tendril.
3

18 TWINING PLANTS. Cuae. L

but took 9 hrs. 30 m. to make one complete spire reund
a stick ; Aristolochia gigas revolved in about 5 hrs., but
took 9 hrs. 15 m. to complete its spire. This, 1 presume,
is due to the continued disturbance of the impelling
force by the arrestment of the movement at successive
points ; and we shall hereafter see that even shaking a
plant retards the revolving movement. The terminal
internodes of a long, much-inclined, revolving shoot of
the Ceropegia, after they had wound round a stick,
always slipped up it, so as to render the spire more
open than it was at first; and this was probably in
part due to the force which caused the revolutions,
being now almost freed from the constraint of gravity
and allowed to act freely. With the Wistaria, on the
other hand, a long horizontal shoot wound itself at
first into a very close spire, which remained un-
changed; but subsequently, as the shoot twined
spirally up its support, it made a much more open
spire. With all the many plants which were allowed
freely to ascend a support, the terminal internodes
made at first a close spire; and this, during windy
weather, served to keep the shoots in close contact
with their support; but as the penultimate internodes
grew in length, they pushed themselves up for a
considerable space (ascertained by coloured marks on
the shoot and on the support) round the stick, and the
spire became more open.*

It follows from this latter fact that the position

* See Dr. H. de Vries (ibid. p. 324) on this subject,

Cuar. L. TWINING PLANTS. 19

occupied by each leaf with respect to the support,
depends on the growth of the internodes after they
have become spirally wound round it. I mention this
on account of an observation by Palm (p. 34), who
states that the opposite leaves of the Hop always stand
in a row, exactly over one another, on the same side
of the supporting stick, whatever its thickness may
be. My sons visited a hop-field for me, and reported
that though they generally found the points of inser-
tion of the leaves standing over each other for a space
of two or three feet in height, yet this never occurred
up the whole length of the pole ; the points of insertion
forming, as might have been expected, an irregular
spire. Any irregularity in the pole entirely destroyed
the regularity of position of the leaves. From casual
inspection, it appeared to me that the opposite leaves
of Thunbergia alata were arranged in lines up the sticks
round which they had twined; accordingly, I raised a
dozen plants, and gave them sticks of various thick-
nesses, as well as string, to twine round; and in this
case one alone out of the dozen had. its leaves
arranged in a perpendicular line: I conclude, therefore,
Palm’s statement is not quite accurate.

The leaves of different twining-plants are arranged
on the stem (before it has twined) alternately, or
oppositely, or in a spire. In the latter case the line of
insertion of the leaves and the course of the revolutions
coincide. This fact has been well shown by Dutrochet,*

* Comptes Rendus, 1844, tom. xix. p. 295, and Annales des Se, Nat,
3rd series, Bot., tom. ii, p. 163,

20 TWINING PLANTS. Cuar. 1

who found different individuals of Solanwn dulcamara
twining in opposite directions, and these had their
leaves in each case spirally arranged in the same direc-
tion. A dense whorl of many leaves would apparently
be incommodious for a twining plant, and some authors
assert that none have their leaves thus arranged; but
a twining Siphomeris has whorls of three leaves.

If a stick which has arrested a revolving shoot, but
has not as yet been encircled, be suddenly taken
away, the shoot generally springs forward, showing
that it was pressing with some force against the stick.
After a shoot has wound round a stick, if this be with-
drawn, it retains for a time its spiral form; it then
straightens itself, and again commences to revolve.
The long, much-inclined shoot of the Ceropegia pre-
viously alluded to offered some curious peculiarities.
The lower and older internodes, which continued to
revolve, were incapable, on repeated trials, of twining
round a thin stick; showing that, although the power
of movement was retained, this was not sufficient
to enable the plant to twine. I then moved the
stick to a greater distance, so that it was struck by
a point 24 inches from the extremity of the penulti-
mate internode; and it was then neatly encircled
by this part of the penultimate and by the ultimate
internode. After leaving the spirally wound shoot for
eleven hours, I quietly withdrew the stick, and in the
course of the day the curled portion straightened
itself and recommenced revolving; but the lower and
not curled portion of the penultimate internode did

Oxar. I, TWINING PLANTS. 21

not move, a sort of hinge separating the moving and
the motionless part of the same internode. After a
few days, however, I found that this lower part had
likewise recovered its revolving power. These.several
facts show that the power of movement is not immedi-
ately lost in the arrested portion of a revolving shoot ;
and that after being temporarily lost it can be recovered.
When a shoot has remained for a considerable time
round a support, it permanently retains its spiral form
even when the support is removed.

When a tall stick was placed so as to arrest the
lower and rigid internodes of the Ceropegia, at the
distance at first of 15 and then of 21 inches from the
centre of revolution, the straight shoot slowly and
gradually slid up the stick, so as to become more and
more highly inclined, but did not pass over the
summit. Then, after an interval sufficient to have
allowed of a semi-revolution, the shoot suddenly
bounded from the stick and fell over to the opposite
side or point of the compass, and reassumed its
previous slight inclination. It now recommenced
revolving in its usual course, so that after a semi-
revolution it again came into contact with the stick,
again slid up it, and again bounded from it and fell
over to the opposite side. This -movement of the
shoot had a very odd appearance, as if it were
disgusted with its failure but was resolved to try
again. We shall, I think, understand this movement
by considering the former illustration of the sapling, in
which the growing surface was supposed to creep round

22 TWINING PLANTS. Cuar, I.

from the northern by the western to the southern
face; and thence back again by the eastern to the
northern face, successively bowing the sapling in all
directions. Now with the Ceropegia, the stick being
placed to the south of the shoot and in contact with
it, as soon as the circulatory growth reached the
western surface, no effect would be produced, except that
the shoot would be pressed firmly against the stick.
But as soon as growth on the southern surface began,
the shoot would be slowly dragged with a sliding move-
ment up the stick; and then, as soon as the. eastern
growth commenced, the shoot would be drawn from the
stick, and its weight coinciding with the effects of the
changed surface of growth, would cause it suddenly to
fall to the opposite side, reassuming its previous slight
inclination; and the ordinary revolving movement
would then go on as before. I have described this
curious case with some care, because it first led me to
understand the order in which, as I then thought, the
surfaces contracted ; but in which, as we now know from
Sachs and H. de Vries, they grow for a time rapidly,
thus causing the shoot to bow towards the opposite
side.

The view just given further explains, as I believe,
a fact observed by Mohl (p. 1385), namely, that a
revolving shoot, though it will twine round an object
as thin as a thread, cannot do so round a thick support.
I placed some long revolving shoots of a Wistaria
close to a post between 5 and 6 inches in diameter,
but, though aided by me in many ways, they. could

Guar. L TWINING PLANTS. 23

not wind round it. This apparently was due to the
flexure of the shoot, whilst winding round an object
so gently curved as this post, not being sufficient to
‘hold the shoot to its place when the growing surface
crept round to the opposite surface of the shoot; so
that it was withdrawn at each revolution from its
support.

When a free shoot has grown far beyond its support,
it sinks downwards from its weight, as already explained
in the case of the Hop, with the revolving extremity
turned upwards. If the support be not lofty, the shoot
falls to the ground, and resting there, the extremity
rises up. Sometimes several shoots, when flexible,
twine together into a cable, and thus support one
another. Single thin depending shoots, such as those
of the Sollya Drummondii, will turn abruptly back-
wards and wind up on themselves. The greater
number of the depending shoots, however, of one
twining plant, the Hibbertia dentata, showed but little
tendency to turn upwards. In other cases, as with the
Cryptostegia grandiflora, several internodes which were
at first flexible and revolved, if they did not succeed in
twining round a support, become quite rigid, and sup-
porting themselves upright, carried on their summits
the younger revolving internodes.

Here will be a convenient place to give a Table
showing the direction and rate of movement of several
twining plants, with a few appended remarks. These
plants are arranged according to Lindley’s ‘ Vegetable
Kingdom’ of 1853 ; and- they have been selected from

Cuap. I,

24 TWINING PLANTS.

all parts of the series so as to show that all kinds
behave in a nearly uniform manner.*

The Rate of Revolution of various Twining Plants.

(ACOTYLEDONS.)
Lygodium scandens (Polypodiacez) moves against the sun.
iH. OM.
June 18, Ist circle was madein . 6 0
» 18,2nd_ ,, o 5 6 15 (late in evening)
» 19,38rd , 4, 9 . 5 32 (very hot day)
, 19,4th ,, 3 ss - 5 0 (very hot day)
ed 20, 5th 2 ”» a” # 6 0

Lygodium articulatum moves against the sun.

HM.

July 19, Ist circle was made in . 16 30 (shoot very young)

» 22nd, » » +1 0
” 21, 8rd a ” ” Le 8 0
» 22,4th 4 yw 10 30

(MonocorTyLEDons.)

Ruscus androgynus (Liliacese), placed in the hot-house, moves
against the sun.

HM.
May 24, Ist circle was made in 6 14 (shoot very young)

» 2,2nd 4 » 9 2 21
» 25,3rd 4, ww 3 87
» 205,4th 5 ow 3 22
» 265th 4, 4» » 2 50
» 27, 0th yy 4 3 52
” 27, 7th etd ” ” 4 ll

* I am much indebted to Dr.

of climbing plants. Professor Asa
Hooker for having sent me many

Gray, Prof. Oliver, and Dr. Hooker

plants from Kew; and to Mr.
Veitch, of the Royal Exotic Nur-
sery, for having generously given

mea collection of fine specimens:

have afforded me, as on many
previous occasions, much infor:
mation and many references,

Cuap. I. TWINING PLANTS.

25

(MonocoryLepons, continued.)

Asparagus (unnamed species from Kew) (Liliacew) moves
against the sun, placed in hothouse.

Dec. 26, Ist circle was made in .

» 27,2nd ,,

Tamus communis (Dioscoreacee). A young shoot from a
tuber in a pot placed in the greenhouse : follows the sun.

July, 7, 1st circle was made in .

» 7, 2nd
8, 8rd
» 8, 4th
» 8, 5th
» 8, 6th

a”

”

”

”

”

HM,
5 0
5 40

HM.

2 30

Lapagerea rosea (Philesiacez), in greenhouse, follows the sun.

March 9, Ist circle was made in .

» 10, semicircle
11, 2nd circle

» 12,3rd ,
, 134th ,
» 16,5th ,

stationary.

»”

”

”

iH. M.
. 26 15 (shoot young)

8 15

_- ill 0
. 15 30
. 1415

8 40 when placed in

the hothouse; but the next day the shoot remained

Roxburghia viridiflora (Roxburghiacee) moves against the
sun; it completed a circle in about 24 hours.

(DicoTYLEDONS.)

Humulus Lupulus (Urticacer) follows the sun. The plant
was kept in a room during warm weather.

April 9,2 circles were made in .
Aug. 13, 8rd circle was

» 14,4th
» 14, 5th
» 14, 6th

14, 7th

» 14, 8th

”

ted

”

DNDnwpnwpnnndee:z
i
ponwmSobs

26 TWINING PLANTS. Cuap. I.

(DicorrLepons, continued.)

With the Hop a semicircle was performed, in travelling
from the light, in 1 hr. 83 m.; in travelling to the light, in
lhr. 13 m.; difference of rate, 20 m.

Akebia quinata (Lardizabalacess), placed in hothouse, moves

against the sun.
H M.

March 17, Ist circle was made in . . 4 0 (shoot young) -
” 18, 2nd ” » ” . . 1 40
sy 88rd) ss ae Ss . . 130
e, 19,4th , » vw» . .145

Stauntonia latifolia (Lardizabalaces), placed in hothouse,

moves against the sun.
HR OM

March 28, Ist circle wasmadein . . 8 30
» 29,2nd , 5» 3 . .845

Spherostema marmoratum (Schizandracez) follows the sun.

HK OM
August 5th, Ist circle was made in about . . 24 0
5th, 2nd circle was madein . . . . 18 80

2”

Stephania rotunda (Menispermacez) moves against the sun.

t HOM.
May 27, 1st circle wasmadein . . .5 5
» 82nd ow ee WT OB
June 2,38rd oy » . .516

3,4th , » » « « «628

a”

Thryallis brachystacnys (Malpighiacesze) moves against the sun:
one shoot made a circle in 12 hrs., and another in 10 hrs, 80 m.;
but the next day, which was much colder, the first shoot took
10 hrs. to perform only a semicircle.

Hibbertia dentata (Dilleniacezx), placed in the hothouse, fol-
lowed the sun, and made (May 18th) a circlein 7 hrs. 20 m.; on
the 19th, reversed its course, and moved against the sun, and
madea circle in 7 hrs.; on the 20th, moved against the sun one-
third of a circle, and then stood still; on the 26th, followed the

Cnar. L TWINING PLAN'IS. 27

(DICOTYLEDONS, continued.)

sun for two-thirds of a circle, and then returned to its starting-
point, taking for this double course 11 hrs, 46 m.

Sollya Drummondit (Pittésporacese) moves against the sun;
kept in greenhouse.

i.
April 4, 1st circle was made in . 4
” 5, 2nd ” » ” = 8 (very cold day)

” 6, 3rd ” ” ” * 6

7, 4th 7
Polygonum dumetorum (Polygonacer). This case is taken
from Dutrochet (p. 299), as I observed, no allied plant: follows
the sun. Three shoots, cut off a plant, and placed in water,

made circles in 3 hrs. 10 m., 5 hrs. 20 m., and 7 hrs. 15 m.

Wistaria Chinensis (Leguminose), in greenhouse, moves
against the sun.

ood ” ” ed .

- HA. MM.

May 13, 1st circle was made in 3 5
” 13, 2nd » ” ” 3 20
» 16,38rd fg ee BO
» 24,4th ,, - 55 x « « BOL
» 25,5th ,, 3 5 2 37
” 25, 6th a ” ” ° 2 oo

Phaseolus vulgaris (Leguminosee), in greenhouse, moves against
the sun.

RR. OM.

May, Ist circle was made in . .2 0

23 2nd 2” » ” . . 1 55

cca 3rd. ” » ” 2 » a * 1 55
Dipladenia urophylla (Apocynaceze) moves against the sun.

H M.

April 18, Ist circle was made in . -8 0

ery 19, 2nd a” ” Pd = 9 15

” 30, 8rd a” ” ” * « . 9 40

Pipladenia crassinoda moves against the sun.

H. M.

May 16, Ist circle was made in . 9 5

July 20, 2nd a” » a * 8 0

» 2,3rd 4, » -8 5

28 TWINING PLANTS, Cuar. L

(DIcoTYLEDONS, continued.)

Ceropegia Gardnerii (Asclepiadacese) moves against the sun.
HK OM,
Shoot very young, 2 inches
inlength . . . .
Shoot stillyoung . . . 2nd , » » » 7 0
Long shoot me Ge ae BI Sa Gy age, 78888
Longshot . . .. . 4h », » » » 515
Long shoot . . . . . Sth , 5» » » 645

Stephanotis floribunda (Asclepiadacese) moves against the sun
and made a circle in 6 hrs. 40 m., a second circle in about 9 hrs.

| et circle was performed in 7 55

Hoya carnosa (Asclepiadacese) made several circles in from
16 hrs. to 22 hrs. or 24 hrs.

Ipomea purpurea (Convolvulaces) moves against the sun.
Plant placed in room with lateral light.

Semicircle, from the light in

1st circle was made in 2 hrs. 42m.; 1 hr. 14 m,, to the light

Lhr. 28 m.: difference 14m.

Semicircle, from the light in

Qnd circle was made in 2 hrs.47m.! 1 hr. 17 m., to the light 1 hr.
30 m.: difference 13 m.

Ipomea jucunda (Convolvulacez) moves against the sun, placed
in my study, with windows facing the north-east. Weather hot.

Semicircle, from the light in
Ast circle was made in 5 hrs.30 m.J 4 hrs. 30 m., to the light 1 hr.
0 m.: difference 3 hrs. 30 m.

and circle was made in 5 hrs. Semicircle, from the light in

20m. (Late in afternoon: 3hrs. 50 m.. to the light 1h
circle completed at 6 hrs. 40m. ( 35 a. Ce att " rs 20 sh
P.M.) j

We have here a remarkable instance of the power of light in
retarding and hastening the revolving movement.

Convolvulus sepium (large-flowered cultivated var) moves
against the sun. Two circles, were made each in 1 hr. 42 m.:
difference in semicircle from and to the light 14 m.

Cuap. 1. TWINING PLANTS. 29

(DicoTyLEDoNs, continued.)

Rivea tiliefolia (Convolvulacee) moves against the sun;
made four revolutions in 9 hrs.; so that, on an average, each
was performed in 2 hrs. 15 m.

Plumbago rosea (Plumbaginacez) follows the sun. The shoot
did not begin to revolve until nearly a yard in height; it then
made a fine circle in 10 hrs. 45m. During the next few days it
continued to move, but irregularly. On August 15th the shoot
followed, during a period of 10 hrs. 40 m., a long and deeply
zigzag course and then made a broad ellipse. The figure
apparently represented three ellipses, each of which averaged
3 hrs. 33 m. for its completion.

Jasminum pauciflorum, Bentham (Jasminaces), moves against
thesun. A circle was made in 7 hrs. 15 m., and a second rather
more quickly.

Clerodendrum Thomsonii (Verbenacee) follows the sun.

BR OM
April 12, Ist circle was made in . 5 45 (shoot very young)
” 14, 2nd ” ” ” . 3 30
(directly after the
» 18, a semicircle 2 . 5 03 plant was shaken
on being moved)
» 19,3rdcircle , ,, . 80
” 20, 4th ” ” ” . 4 90

Tecoma jasminoides (Bignoniaces) moves against the sun.

HR M
March 17, Ist circle was madein . 6 30
” 19, 2nd. » ” ” . 7 0

» 22,8rd 4, » 5 . 8 80 (very cold day)
24, 4th ” ” ” . 645

Lhunbergia alata (Acanthacee) moves against sun.

or

H M
April 14, Ist circle was made in . 3 20
2 18, 2nd ” ” zd . 2 50

» 18, 3rd ” ” ” . 2 55
» 18,4th ,, 3 os . 38 55 (late in afternoon)

30 TWINING PLANTS. Cuap. I.

(DicoTYLEDONS, continued.)

Adhadota cydonefolia (Acanthacez) follows the sun. A young
shoot made a semicircle in 24 hrs.; subsequently it made a
circle in between 40 hrs. and 48 hrs. Another shoot, however,
made a circle in 26 hrs. 30 m.

Mikania scandens (Composite) moves against the sun.
H OM
March 14, Ist circle was made in 3 10
» 15,9nd , 4, » 8 O
» 16,3rd , 4 » 38 O
” 17, 4th a” a ” 3 33
April 7, 5th 2
This circle was made
» 76th , 2 40) after a copious water-
or ee SEG ing with cold water at
47° Fahr.

Combretum argenteum (Combretaces:) moves against the sun.
Kept in hothouse.

HR M.
Early in morning, when
Jan. 24, Ist circle was made in 2 55; the temperature of the

house had fallen a little.
» 24, 2 circles each at an

average of. . t 2 20
» 25, 4th circle was made in 2 25

Combretum purpureum revolves not quite so quickly as C.
argenteum.

Loasa aurantiaca (Loasacez). Revolutions variable in their
course: a plant which moved against the sun.

HK MM,

June 20, Ist circle was made in . . 237
» 20,2nd 5 4,45 . 218
» 20, 3rd 2) oe ” «4 0
» 214th , 4» 4 . 2 35

» 22,5th ,, ee « « « B26
” 23, 6th ” ” ” eg 3 5

Cuar. I. TWINING PLANTS. 31

(DicoTYLEDONS, continued.)

Another plant which followed the sun in its revolutions.
H. OM.

July 11, Ist circle was madein . . .1 51
”» 11, 2nd 2 » a” + . . 1 46
» 3d , : i ad Very hot day.
» llj4th , » » « « - 148

12,5th , » » » . « 235

”

H. OM,

June 18, 1st circle was made in . 1 45
» 18,2nd , 45 » 117
» 14,8rd. , 4% 7 . 136

» 44th 5 » » - . 159

» 14,5th ,, oe SS ‘ » 233)

Siphomeris or Lecontea (unnamed sp.) (Cinchcnacez) follows
the sun.

(shoot extremely

young)

» 26,%st circle ,, a . 10 15 (shoot still young)

» 80,2nd 5 4 4 «+ 855
June 2,3rd_—,, 3 yi . 811

» 6, 4th 6 8

Taken from the

10 hothouse, and
6 placed in a room
in my house.

HR OM
May 25, semicircle was made in . 10 27 \

” ed a”

Ed

8, 5th ” ” BB) s. 7 2
9, 6th ” ” ” 8 3

”

Manettia bicolor (Cinchonacee), young plant, follows the sun.

July 7, 1st circle wasmadein . . . 6 18
» 82nd 5 le ee 6 BB
9, ard. ” ” a3 . . « 6 30

7

Lonicera brachypoda (Caprifoliacez) follows the sun, kept in a

warm room in the house.
Mw.

H. .
April, 1st circle was made in. 9 10 (about)

32 TWINING PLANTS. Cuar. 1.

(DicoTYLEDons, continued.)

(a distinct shoot, very

H M
April, 2nd circle was made in 12 20 1 young, on same plant)

» ord se ” . 780
n this latter circlo,

the semicircle from
the light took 5 hrs,
» 4th ,, 4” - 80 23 m., and to the
light 2 hrs. 37 min.:
difference 2 hrs 46m.

Aristolochia gigas (Aristolochiacez) moves against the sun.

July 22, 1st circle was madein . 8 0 (rather young shoot)
a” 23, 2nd 7 ” ” . 7 15
24,3rd 5 oy os . 5 0 (about)

In the foregoing Table, which includes twining
plants belonging to widely different orders, we see
that the rate at which growth travels or circulates
round the axis (on which the revolving movement
depends), differs much. As long as a plant remains
under the same conditions, the rate is often remarkably
uniform, as with the Hop, Mikania, Phaseolus, &c. The
Scyphanthus made one revolution in I] hr. 17 m., and
this is the quickest rate observed by me; but we shall
hereafter see a tendril-bearing Passiflora revolving
more rapidly. A shoot of the Akebia quinata made a
revolution in 1 hr. 30 m., and three revolutions at the
average rate of 1 hr. 38 m.; a Convolvulus made two
revolutions at the average of 1 hr. 42 m., and Phaseolus
vulgaris three at the average of 1 hr. 57m. On the
other hand, some plants take 24 hrs. for a single
revolution, and the Adhadota sometimes required
48 hrs.; yet this latter plant is an efficient twiner.

Cuap. L TWINING PLANTS. 33

Species of the same genus move at different rates.
The rate does not seem governed by the thickness of
the shoots: those of the Sollya are as thin and flexible
as string, but move more slowly than the thick and
fleshy shoots of the Ruscus, which seem little fitted for
movement of any kind. The shoots of the Wistaria,
which become woody, move faster than those of the
herbaceous Ipomoea or Thunbergia.

We know that the internodes, whilst still very
young, do not acquire their proper rate of movement ;
hence the several shoots on the same plant may some-
times be seen revolving at different rates. The two or
three, or even more, internodes which are first formed
above the cotyledons, or above the root-stock of a
perennial plant, do not move; they can support them-
selves, and nothing superfluous is granted.

A greater number of twiners revolve in a course
opposed to that of the sun, or to the hands of a watch,
than in the reversed course, and, consequently, the
majority, as is well known, ascend their supports from
left to right. Occasionally, though rarely, plants of
the same order twine in opposite directions, of which
Mohl (p. 125) gives a case in the Leguminose, and we
have in the table another in the Acanthacee. I have
seen no instance of two species of the same genus
twining in opposite directions, and such cases must be
rare ; but Fritz Miller * states that although Mikania

* Journal of the Linn. Soc. interesting paper, in which he
<Bot.) vol. ix. p. 344. I shall corrects or confirms various state-
have occasion often to quote this ments made by me.

34 TWINING PLANTS. Cuap. L

scandens twines, as I have described, from left to right,
another species in South Brazil twines in an opposite
direction. It would have been an anomalous circum-
stance if no such cases had occurred, for different
individuals of the same species, namely, of Solanum
duleamara (Dutrochet, tom. xix. p. 299), revolve and
twine in two directions: this plant, however, is a most
feeble twiner. Loasa aurantiaca (Léon, p. 351) offers
a much more curious case: I raised seventeen plants:
of these 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,* the petioles of the opposite leaves affording a
point dapput for the reversal of the spire. One of
these four plants made seven spiral turns from right
to left, and five turns from left to right. Another
plant in the same family, the Scyphanthus elegans,
habitually twines in this same manner. I raised
many plants of it, and the stems of all took one
turn, or occasionally two or even three turns in
one direction, and then, ascending for a short space
straight, reversed their course and took one or two
turns in an opposite direction. The reversal of
the curvature occurred at any point in the stem,
even in the middle of an internode. Had I not
seen this case, I should have thought its occurrence

* I raised nine plants of the of these also reversed their spire
hybrid ZLoasa Herhertit, and six in ascending a support.

Cuar. L. TWINING PLANTS. 35

most improbable. It would be hardly possible with
any plant which ascended above a few feet in height,
or which lived in an exposed situation; for the stem
could be pulled away easily from its support, with but
little unwinding ; nor could it have adhered at all,
had not the internodes soon become moderately rigid.
With leaf-climbers, as we shall soon see, analogous
cases frequently occur ; but these present no difficulty,
as the stem is secured by the clasping petioles.

In the many other revolving and twining plants
observed by me, I never but twice saw the movement
reversed ; once, and only for a short space, in Ipomoea
jucunda ; but frequently with Hibbertia dentata. This
plant at first perplexed me much, for I continually
observed its long and flexible shoots, evidently well
fitted for twining, make a whole, or half, or quarter
circle in one direction and then in an opposite
direction; consequently, when I placed the shoots
near thin or thick sticks, or perpendicularly stretched
string, they seemed as if constantly trying to ascend,
but always failed. J then surrounded the plant with a
mass of branched twigs; the shoots ascended, and
passed through them, but several came out laterally, and
their depending extremities seldom turned upwards as
is usual with twining plants. Finally, I surrounded
a second plant with many thin upright sticks, and
placed it near the first one with twigs; and now
both had got what they liked, for they twined up
-the parallel sticks, sometimes winding round one and
sometimes round several; and the shoots travelled

36 TWINING PLANTS. Cuar. I

laterally from one to the other pot; but as the
plants grew older, some of the shoots twined regu-
larly up thin upright sticks. Though the revolving
movement was sometimes in one direction and some-
times in the other, the twining was invariably from
left to right ;* so that the more potent or persistent
movement of revolution must have been in opposition
to the course of the sun. It would appear that this
Hibbertia is adapted both to ascend by twining, and to
ramble laterally through the thick Australian scrub.

I have described the above case in some detail,
because, as far as I have seen, it is rare to find any
special adaptations with twining plants, in which
respect they differ much from the more highly organ-
ized tendril-bearers. The Solanum dulcamara, as we
shall presently see, can twine only round stems which
are both thin and flexible. Most twining plants are
adapted to ascend supports of moderate though of
different thicknesses. Our English twiners, as far as
I have seen, never twine round trees, excepting the
honeysuckle (Lonicera periclymenum), which I have
observed twining up a young beech-tree nearly 44
inches in diameter. Mohl (p. 134) found that the
Phaseolus multiflorus and Ipomoea purpurea could not,

* In another genus, namely left; and Ionce saw a shoot which
Davilla, belonging to the same ascended a tree about five inches
family with Hibbertia, Fritz in diameter, reverse its course in
Miller says (ibid. p. 349) that the same manner as so frequently .
“the stem twines indifferently occurs with Loasa.”’
from left to right, or from right to

Cup. I. TWINING PLANTS. 37

when placed in a room with the light entering on one
side, twine round sticks between 3 and 4 inches in
diameter ; for this interfered, in a manner presently
to be explained, with the revolving movement. In the
open air, however, the Phaseolus twined round a
support of the above thickness, but failed in twining
round one 9 inches in diameter. Nevertheless, some
twiners of the warmer temperate regions can manage
this latter degree of thickness; for 1 hear from
Dr. Hooker that at Kew the Ruscus androgynus has
ascended a column 9 inches in diameter ; and although
a Wistarta grown by me in a small pot tried in vain
for weeks to get round a post between 5 and 6 inches
in thickness, yet at Kew a plant ascended a trunk
above 6 inches in diameter. The tropical twiners, on
the other hand, can ascend thicker trees; I hear from
Drs. Thomson and Hooker that this is the case with
the Butea parviflora, one of the Menispermacesx, and
with some Dalbergias and other Leguminose.* This
power would be necessary for any species which had
to ascend by twining the large trees of a tropical forest ;
otherwise they would hardly ever be able to reach the
light. In our temperate countries it would be injurious
to the twining plants which die down every year if

* Fritz Miiller states (ibid. p. ispermacez. He adds in his
349) that he saw on one occasionin letter to me that most of the
the forests of South Brazila trunk climbing plants which there
about five feet in circumference ascend thick trees, are root-
spirally ascended by a plant, climbers; some being tendril-
apparently belonging to the Men- _ bearers.

38 TWINING PLANTS. Cuar. I.

they were enabled to twine round trunks of trees, for
they could not grow tall enough in a single season to
reach the summit and gain the light.

By what means certain twining plants are adapted to
ascend only thin stems, whilst others can twine round
thicker ones, I do not know. It appeared to me
probable that twining plants with very long revolving
shoots would be able to ascend thick supports ; accord-
ingly I placed Ceropegia Gardnerit near a post 6
inches in diameter, but the shoots entirely failed to
wind round it; their great length and power of move-
ment merely aid them in finding a distant stem
round which to twine. The Sphxrostemma marmora-
tum is a vigorous tropical twiner; and as it is a very
slow revolver, I thought that this latter circumstance
might help it in ascending a thick support ; but though
it was able to wind round a 6-inch post, it could do
this only on the same level or plane, and did not
form a spire and thus ascend.

As ferns differ so much in structure from phanero-
gamic plants, it may be worth while here to show that
twining ferns do not differ in their habits from other
twining plants. In Lygodiwm articulatum the two
internodes of the stem (properly the rachis) which
are first formed above the root-stock do not move;
the third from the ground revolves, but at first very
slowly. This species is a slow revolver: but L.
scandens made five revolutions, each at the average
rate of 5hrs. 45 m.; and this represents fairly well the
usual rate, taking quick and slow movers, amongst

Cuar. IL. TWINING PLANTS, 39

phanerogamic plants. The rate was accelerated by
increased temperature. At each stage of growth only
the two upper internodes revolved. <A line painted
along the convex surface of a revolving internode
becomes first lateral, then concave, then lateral and
ultimately again convex. Neither the internodes nor
the petioles are irritable when rubbed. The movement
is in the usual direction, namely, in opposition to the
course of the sun; and when the stem twines round a
thin stick, it becomes twisted on its own axis in the same
direction. After the young internodes have twined
round a stick, their continued growth causes them to
slip a little upwards. If the stick be soon removed,
they straighten themselves, and recommence revolving.
The extremities of the depending shoots turn upwards,
and twine on themselves. In all these respects we
have complete identity with twining phanerogamic
plants; and the above enumeration may serve as a
summary of the leading characteristics of all twining
plants.

The power of revolving depends on the general
health and vigour of the plant, as has been laboriously
shown by Palm. But the movement of each separate
internode is so independent of the others, that cutting
off an upper one does not affect the revolutions of a
lower one.. When, however, Dutrochet cut off two
whole shoots of the Hop, and placed them in water, the
movement was greatly retarded; for one revolved in
20 hrs. and the other in 23 hrs., whereas they ought
to have revolved in between 2 hrs. and 2 hrs. 30 m.

40 TWINING PLANTS. Cuar. I.

Shoots of the Kidney-bean, cut off and placed in
water, were similarly retarded, but in a less degree,
I have repeatedly observed that carrying a plant from
the greenhouse to my room, or from one part to
another of the greenhouse, always stopped the move-
ment for a time; hence I conclude that plants in a
state of nature and growing in exposed situations,
would not make their revolutions during very stormy
weather. A decrease in temperature always caused a
considerable retardation in the rate of revolution; but
Dutrochet (tom. xvii. pp. 994, 996) has given such
precise observations on this head with respect to the
common pea that 1 need say nothing more. When
twining plants are placed near a window in a room,
the light in some cases has a remarkable power
(as was likewise observed by Dutrochet,. p. 998, with
the pea) on the revolving movement, but this differs
in degree with different plants; thus Ipomea jucunda
made a eomplete circle in 5 hrs. 30m.; the semi-
circle from the light taking 4 hrs. 30 m., and that
towards the light only 1 hr. Lonicera brachypoda
revolved, in a reversed direction to the Ipomea, in
8 hrs.; the semicircle from the light taking 5 hrs. 23 m.,
and that to the light only 2 hrs. 37 m. From the
rate of revolution in all the plants observed by me,
being nearly the same during the night and the
day, I infer that the action of the light is confined to
retarding one semicircle and accelerating the other,
so as not to modify greatly the rate of the whole
revolution. This action of the light is remarkable,

Cuar. L TWINING PLANTS. 41

when we reflect how little the leaves are developed on
the young and thin revolving internodes. It is all
the more remarkable, as botanists believe (Mohl,
p. 119) that twining plants are but little sensitive
to the action of light.

I will conclude my account of twining plants by
giving a few miscellaneous and curious cases. With
most twining plants all the branches, however many
there may be, go on revolving together; but, ac-
cording to Mohl (p. 4), only the lateral branches of
Tamus elephantipes twine, and not the main stem.
On the other hand, with a climbing species of Aspa-
ragus, the leading shoot alone, and not the branches,
revolved and twined ; but it should be stated that the
plant was not growing vigorously. My plants of
Combretum argenteum and C. purpureum made nume-
rous short healthy shoots; but they showed no signs
of revolving, and I could not conceive how these
plants could be climbers ; but at last C. argenteum put
forth from the lower part of one of its main branches
a thin shoot, 5 or 6 feet in length, differing greatly
in appearance from the previous shoots, owing to its
leaves being little developed, and this shoot re-
volved vigorously and twined. So that this plant
produces shoots of two kinds. With Periploca Greca
(Palm, p. 43) the uppermost shoots alone twine.
Polygonum convolvulus twines only during the middle
of the summer (Palm, p. 43, 94); and plants growing
vigorously in the autumn show no inclination to

climb. The majority of Asclepiadacew are twiners ;
3

42 TWINING PLANTS. Cuar. I,

but Asclepias nigra only “in fertiliori solo incipit
scandere subvolubili caule” (Willdenow, quoted and
confirmed by Palm, p. 41). Asclepias vincetoxicum does
not regularly twine, but occasionally does so (Palm,
p- 42; Mohl, p. 112) when growing under certain
conditions. So it is with two species of Ceropegia, as I
hear from Prof. Harvey, for these plants in their
native dry South African home generally grow erect,
from 6 inches to 2 feet in height,—a very few taller
specimens showing some inclination to curve; but
when cultivated near Dublin, they regularly twined
up sticks 5 or 6 feet in height. Most Convolvulacex
are excellent twiners; but in South Africa Ipomea
argyreoides almost always grows erect and compact,
from about 12 to 18 inches in height, one specimen
alone in Prof. Harvey’s collection showing an evident
disposition to twine. On the other hand, seedlings
raised near Dublin twined up sticks above 8 feet in
height. These facts are remarkable; for there can
hardly be a doubt that in the dryer provinces of
South Africa these plants have propagated themselves
for thousands of generations in an erect condition;
and yet they have retained during this whole period
the innate power of spontaneously revolving and
twining, whenever their shoots become elongated
under proper conditions of life. Most of the species
of Phaseolus are twiners; but certain varieties of the
P. multiflorus produce (Léon, p. 681) two kinds of
shoots, some upright and thick, and others thin and
twining. I have seen striking instances of this curious

Caar. I. TWINING PLANTS. 43

case of variability in “Fulmer’s dwarf forcing-bean,”
which occasionally produced a single long twining
shoot.

Solanum dulcamara is one of the feeblest and
poorest of twiners: it may often be seen growing as
an upright bush, and when growing in the midst of
a thicket merely scrambles up between the branches
without twining; but when, according to Dutrochet
(tom. xix. p. 299), it grows near a thin and flexible
support, such as the stem of a nettle, it twines round
it. I placed sticks round several plants, and vertically
stretched strings close to others, and the strings alone
were ascended by twining. The stem twines in-
differently to the right or left. Some others pecies
of Solanum, and of another genus, viz. Habrothamnus,
belonging to the same family, are described in horti-
cultural works as twining plants, but they seem to
possess this faculty in a very feeble degree. We may
suspect that the species of these two genera have as
yet only partially acquired the habit of twining. On
the other hand with Tecoma radicans, a member of a
family abounding with twiners and tendril-bearers, but
which climbs, like the ivy, by the aid of rootlets, we
may suspect that a former habit of twining has been
lost, for the stem exhibited slight irregular movements
which could hardly be accounted for by changes in the
action of the light. There is no difficulty in under-
standing how a spirally twining plant could graduate
into a simple root-climber; for the young internodes
of Bignonia Tweedyana and of Hoya carnosa revolve

44 TWINING PLANTS. Cuar. L

and twine, but likewise emit rootlets which adhere to
any fitting surface, so that the loss of twining would
be no great disadvantage and in some respects an
advantage to these species, as they would then ascend
their supports in a more direct line.*

~* Fritz Miiller has published climbing plants in ‘ Bot. Zeitung,’
some interesting facts and views 1866, pp. 57, 65,
on the structure of the wood of

Czar. IL LEAF-CLIMBERS. 45

CHAPTER II.

Lear-CLimsers.

Plants which limb by the aid of spontaneously revolving and sensitive
petioles — Clematis — Tropzolum — Maurandia, flower-peduncles
moving spontaneously and sensitive to a touch—Rhodochiton—
Lophospermum— internodes sensitive — Solanum, thickening of
the clasped petioles—Fumaria—Adlumia—Plants which climb by
the aid of their produced midribs— Gloriosa — Flagellaria—
Nepenthes—Summary on leaf-climbers.

WE now come to our second class of climbing plants,
namely, those which ascend by the aid of irritable or
sensitive organs. For convenience’ sake the plants
in this class have been grouped under two sub-divisions,
namely, leaf-climbers, or those which retain their
leaves in a functional condition, and tendril-bearers.
But these sub-divisions graduate into each other, as
we shall see under Corydalis and the Gloriosa lily.

It has long been observed that several plants climb
by the aid of their leaves, either by their petioles (foot-
stalks) or by their produced midribs; but beyond this
simple fact they have not been described. Palm and
Mohl class these plants with those which bear tendrils ;
but as a leaf is generally a defined object, the present
classification, though artificial, has at least some advan-
tages. Leaf-climbers are, moreover, intermediate in
many respects between twiners and tendril-bearers.
Eight species of Clematis and seven of Trepewolum were

46 LEAF-CLIMBERS. Cuar. IL

observed, in order to see what amount of difference
in the manner of climbing existed within the same
genus; and the differences are considerable.
Curmatis.—C. glandulosa.—The thin upper inter-
nodes revolve, moving against the course of the sun,
precisely like those of a true twiner, at an average
rate, judging from three revolutions, of 3 hrs. 48 m.
The leading shoot immediately twined round a stick
placed near it; but, after making an open spire of
only one turn and a half, it ascended for a short space
straight, and then reversed its course and wound two
turns in an opposite direction. This was rendered
possible by the straight piece between the opposed
spires having become rigid. The simple, broad, ovate
leaves of this tropical species, with their short thick
petioles, seem but ill-fitted for any movement; and
whilst twining up a vertical stick, no use is made of
them. Nevertheless, if the footstalk of a young leaf
be. rubbed with a thin twig a‘few times on any side,
it will in the course of a few hours bend to that side;
afterwards becoming straight again. The under side
seemed to be the most sensitive; but the sensitiveness
or irritability is slight compared to that which we
shall meet with in some of the following species ; thus,
a loop of string, weighing 1°64 grain (106-2 mg.)
and hanging for some days on a young footstalk,
produced a scarcely perceptible effect. A sketch is
here given of two young leaves which had naturally
eaught hold of two thin branches. A forked twig placed
so as to press lightly on the under side of a young

Cuap. II. CLEMATIS, 47

footstalk caused it, in 12 hrs. to bend greatly, and
ultimately to such an extent that the leaf passed to
the opposite side of the stem; the forked stick having
been removed, the leaf slowly recovered its former
position.

The young leaves spontaneously and gradually change
their position: when first developed the petioles are
upturned and parallel to the stem; they then slowly
bend downwards, remaining for a short time at right

Fig. 1.

Clematis glandulosa.
With two young leaves clasping two twigs, with the clasping portions thickened

angles to the stem, and then become so much arched
downwards that the blade of the leaf points to the
ground with its tip curled inwards, so that the whole
petiole and leaf together form a hook. They are thus
enabled to catch hold of any twig with which they
may be brought into contact by the revolving move-
ment of the internodes. If this does not happen, they
retain their hooked shape for a considerable time, and
then bending upwards reassume their original upturned

48 LEAF-CLIMBERS. Cuar, II,

position, which is preserved ever afterwards. The
petioles which have clasped any object soon become
much thickened and strengthened, as may be seen
in the drawing.

Clematis montana.—The long, thin petioles of the
leaves, whilst young, are sensitive, and when lightly
rubbed bend to the rubbed side, subsequently becom-
ing straight. They are far more sensitive than the
petioles of C. glandulosa ; for a loop of thread weighing
a quarter of a grain (16-2 mg.) caused them to bend;
a loop weighing only one-eighth of a grain (8:1 mg.)
sometimes acted and sometimes did not act. The
sensitiveness extends from the blade of the leaf to
the stem. I may here state that I ascertained in
all cases the weights of the string and thread used
by carefully weighing 50 inches in a chemical balance,
and then cutting off measured lengths. The main
petiole carries three leaflets; but their short, sub-
petioles are not sensitive. A young, inclined shoot
(the plant being in the greenhouse) made a large
circle opposed to the course of the sun in 4 hrs. 20 m.,
but the next day, being very cold, the time was
5hrs.10m. A stick placed near a revolving stem was
soon struck by the petioles which stand out at right
angles, and the revolving movement was thus arrested.
The petioles then began, being excited by the contact,
to slowly wind round the stick. When the stick was
thin, a petiole sometimes wound twice round it.
The opposite leaf was in no way affected. The atti-
tude assumed by the stem after the petiole had

Cuar. IL CLEMATIS. 49

clasped the stick, was that of a man standing by a
column, who throws his arm horizontally round it.
With respect to the stem’s power of twining, some
remarks will be made under C. calycina.

Clematis Sieboldi—aA shoot made three revolutions
against the sun at an average rate of 3hrs. 11m. The
power of twining is like that of the last species. Its
leaves are nearly similar in structure and in function,
excepting that the sub-petioles of the lateral and
terminal leaflets are sensitive. A loop of thread,
weighing one-eighth of a grain, acted on the main
petiole, but not until two or three days had elapsed.
The leaves have the remarkable habit of spon-
taneously revolving, generally in vertical ellipses, in
the same manner, but in a less degree, as will be
described under C. microphylla.

Clematis calycina.—The young shoots are thin and
flexible: one revolved, describing a broad oval, in
5 hrs. 30 m., and another in 6 hrs. 12m. They followed
the course of the sun; but the course, if observed long
enough, would probably be found to vary in this species,
as well as in all the others of the genus. It is a rather
better twiner than the two last species: the stem some-
times made two spiral turns round a thin stick, if free
from twigs; it then ran straight up for a space, and
reversing its course took one or two turns in an
opposite direction. This reversal of the spire occurred
in all the foregoing species. The leaves are so small
compared with those of most of the other species, that
the petioles at first seem ill-adapted for clasping.

50 LEAF-CLIMBERS. Cuar, IL

Nevertheless, the main service of the revolving move-
ment is to bring them into contact with surrounding
objects, which are slowly but securely seized. The
young petioles, which alone are sensitive, have their
ends bowed a little downwards, so as to be in a slight
degree hooked ; ultimately the whole leaf, if it catches
nothing, becomes level. I gently rubbed with a thin
twig the lower surfaces of two young petioles; and in
2hrs. 30 m. they were slightly curved downwards; in
5 hrs., after being rubbed, the end of one was bent
completely back, parallel to the basal portion ; in 4 hrs.
subsequently it became nearly straight again. To
show how sensitive the young petioles are, I may
mention that I just touched the under sides of two
with a little water-colour, which when dry formed
an excessively thin and minute: crust; but this
sufficed in 24hrs. to cause both to bend downwards.
Whilst the plant is young, each leaf consists of three
divided leaflets, which barely have distinct petioles,
and these are not sensitive; but when the plant is
well grown, the petioles of the two lateral and terminal
leaflets are of considerable length, and become sensi-
tive so as to be capable of clasping an object: i in any
direction.

When a petiole has clasped a twig, it undergoes
some remarkable changes, which may be observed
with the other species, but in a less strongly marked
manner, and will here be described once for all. The
clasped petiole in the course of two or three days
swells greatly, and ultimately becomes nearly twice as

Cuap. IL. CLEMATIS. 51

thick as the opposite one which has clasped nothing.
When thin transverse slices of the two are placed
under the microscope their difference is conspicuous:
the side of the petiole which has been in contact with
the support, is formed of a layer of colourless cells with
their longer axes directed from the centre, and these
are very much larger than the corresponding cells
in the opposite or unchanged petiole; the central
cells, also, are in some degree enlarged, and the whole
is much indurated. The exterior surface generally
becomes bright red. But a far greater change takes
place in the nature of the tissues than that which is
visible: the petiole of the unclasped leaf is flexible
and can be snapped easily, whereas the clasped one
acquires: an extraordinary degree of toughness and
rigidity, so that considerable force is required to pull
it into pieces. With this change, great durability is
probably acquired ; at least this is the case with the
clasped petioles of Clematis vitalba. The meaning of
these changes is obvious, namely, that the petioles may
firmly and durably support the stem.

Clematis microphylla, var. leptophylla—The long
and thin internodes of this Australian species revolve
sometimes in one direction and sometimes in an op-
posite one, describing long, narrow, irregular ellipses
or large circles. Four revolutions were completed
within five minutes of the same average rate of
1 hr. 51m.; so that this species moves more quickly
than the others of the genus. The shoots, when placed
near a vertical stick, either twine round it, or clasp it

52 LEAF-CLIMBERS. Cuap, IL

with the basal portions of their petioles. The leaves
whilst young are nearly of the same shape as those
of C. viticella, and act in the same manner like a hook,
as will be described under that species. But the leaflets
are more divided, and each segment whilst young
terminates in a hardish point, which is much curyed
downwards and inwards ; so that the whole leaf readily
catches hold of any neighbouring object. The petioles
of the young terminal leaflets are acted on by loops
of thread weighing }th and even +)th of a grain,
The basal portion of the main petiole is much
less sensitive, but will clasp a stick against which it
presses.

The leaves, whilst young, are continually and sponta-
neously moving slowly. A bell-glass was placed over
a shoot secured to a stick, and the movements of the
leaves were traced on it during several days. A very
irregular line was generally formed ; but one day, in
the course of- eight hours and three quarters, the
figure clearly represented three and a half irregular
ellipses, the most perfect one of which was completed
in 2hrs. 35m. The two opposite leaves moved
independently of each other. This movement of the
leaves would aid that of the internodes in bringing
the petioles into contact with surrounding objeets.
I discovered this movement too late to be enabled to
observe it in the other species; but from analogy I
can hardly doubt that the leaves of at least C. viticella,
C. flammula, and C. vitalba move spontaneously ; and,
judging from C. Steboldi, this probably is the case with

Cuap. IL CLEMATIS, 53

C. montana and C. calycina. I ascertained that the
simple leaves of C. glandulosa exhibited no sponta-
neous revolving movement.

Clematis viticella, var. venosa.—In this and the two
following species the power of spirally twining is
completely lost, and this seems due to the lessened
flexibility of the internodes and to the interference
caused by the large size of the leaves. But the re-
volving movement, though restricted, is not lost. In
our present species a young internode, placed in front
of a window, made three narrow ellipses, transversely
to the direction of the light, at an average rate of
2hrs. 40m. When placed so that the movements were
to and from the light, the rate was greatly accelerated
in one half of the course, and retarded in the other, as
with twining plants. The ellipses were small; the
longer diameter, described by the apex of a shoot
bearing a pair of not expanded leaves, was only 43
inches, and that by the apex of the penultimate inter-
node only 1} inch. At the most favourable period of
growth each leaf would hardly be carried to and fro
by the movement of the internodes more than two or
three inches, but, as above stated, it is probable that
the leaves themselves move spontaneously. The move-
ment of the whole shoot by the wind and by its rapid
growth, would probably be almost equally efficient as
these spontaneous movements, in bringing the petioles
into contact with surrounding objects.

The leaves are of large size. ach bears three pairs
of lateral leaflets and a terminal one, all supported on

54 LEAF-CLIMBERS. Cuar. IL.

rather long sub-petioles.. The main petiole bends a
little angularly downwards at each point where a pair
of leaflets arises (see fig. 2), and the petiole of the
terminal leaflet is bent downwards at right angles;
hence the whole petiole, with its rectangularly bent
extremity, acts as a hook. This hook, the lateral
petioles being directed a little upwards, forms an
excellent grappling apparatus, by which the leaves

Fig. 2.
A young leaf of Clematis viticella.

readily become entangled with surrounding objects.
If they catch nothing, the whole petiole ultimately
grows straight. The main petiole, the sub-petioles,
and the three branches into which each basi-lateral
sub-petiole is generally subdivided, are all sensitive.
The basal portion of the main petiole, between the
stem and the first pair of leaflets, is less sensitive
than the remainder; it will, however, clasp a stick

Cuar. IL. CLEMATIS. 59

with which it is left in contact. The inferior surface
of the rectangularly bent terminal portion (carrying
the terminal leaflet), which forms the inner side of the
end of the hook, is the most sensitive part; and this
portion is manifestly best adapted to catch a distant
support. To show the difference in sensibility, I
gently placed loops of string of the same weight (in
one instance weighing only ‘82 of a grain or 53:14 mg.)
on the several lateral sub-petioles and on the terminal
one; in a few hours the latter was bent, but after
24 hrs. no effect was produced on the other sub-petioles.
Again, a terminal sub-petiole placed in contact with a
thin stick became sensibly curved in 45m., and in
Lhr. 10m. moved through ninety degrees; whilst
a lateral sub-petiole did not become sensibly curved
until 3hrs. 30m. had elapsed. In all cases, if the
sticks are taken away, the petioles continue to move
during many hours afterwards; so they do after a
slight rubbing; but they become straight again, after
about a day’s interval, that is if the flexure has not
been very great or long continued.

The graduated difference in the extension of the
sensitiveness in the petioles of the above-described
species deserves notice. In C. montana it is confined
to the main petiole, and has not spread to the sub-
petioles of the three leaflets; so it is with young plants
of C. calycina, but in older plants it spreads to the
three sub-petioles. In C. viticella the sensitiveness has
spread to the petioles of the seven leaflets, and to the
subdivisions of the basi-lateral sub-petioles. But in

56 LEAF-CLIMBERS. Cuap. IL

this latter species it has diminished in the basal part
of the main petiole, in wnich alone it resided in C.
montana; whilst it has increased in the abruptly bent
terminal portion.

Clematis flammula.—The rather thick, straight, and
stiff shoots, whilst growing vigorously in the spring,
make small oval revolutions, following the sun in their
course. Four were made at an average rate of 3 hrs,
45m. The longer axis of the oval, described by the
extreme tip, was directed at right angles to the line
joining the opposite leaves; its length was in one case
only 12, and in another case 1§ inch; so that the
young leaves were moved a very short distance. The
shoots of the same plant observed in midsummer,
when growing not so quickly, did not revolve at all.
I cut down another plant in the early summer, so that
by August Ist it had formed new and moderately
vigorous shoots; these, when observed under a bell-
glass, were on some days quite stationary, and on
other days moved to and fro only about the eighth of
an inch. Consequently the revolving power is much
enfeebled in this species, and under unfavourable cir-
cumstances is completely lost. The shoot must depend
for coming into contact with surrounding objects on the
probable, though not ascertained spontaneous move-
ment of the leaves, on rapid growth, and on movement
from the wind. Hence, perhaps, it is that the petioles
have acquired a high degree of sensitiveness as a com-
pensation for the little power of movement in the shoots.

The petioles are bowed downwards, and have the

Cuap. IT. CLEMATIS. 57
same general hook-like form as in C. viticella. The
medial petiole and the lateral sub-petioles are sensitive,
especially the much bent terminal portion. As the
sensitiveness is here greater than in any other species
of the genus observed by me, and is in itself remark-
able, I will give fuller details. The petioles, when so
" young that they have not separated from one another,
are not sensitive; when the lamina of a leaflet has
grown to a quarter of an inch in length (that is, about
one-sixth of its full size), the sensitiveness is highest;
but at this period the petioles are relatively much
more fully developed than are the blades of the leaves.
Full-grown petioles are not in the least sensitive. A
thin stick placed so as to press lightly against a
petiole, having a leaflet a quarter of an inch in length,
caused the petiole to bend in 3hrs, 15m. In another
case a petiole curled completely round a stick in
12hrs. These petioles were left curled for 24 hrs., and
the sticks were then removed; but they never
straightened themselves. I took a twig, thinner than
the petiole itself, and with it lightly rubbed several
petioles four times up and down; these in 1 hr. 45 m.
became slightly curled ; the curvature increased during
some hours and then began to decrease, but after 25 hrs.
from the time of rubbing a vestige of the curvature re-
mained. Some other petioles similarly rubbed twice, that
is, once up and once down, became perceptibly curved
in about 2 hrs. 30 m., the terminal sub-petiole moving
more than the lateral sub-petioles; they all became
straight again in between 12hrs.and 14hrs. Lastly, a

58 LEAF-CLIMBERS. Cuar. IL

length of about one-eighth of an inch of a sub-petiole,
was lightly rubbed with the same twig only once; it
became slightly curved in 3 hrs., remaining so during
11 hrs., but by the next morning was quite straight.
The following observations are more precise. After
trying heavier pieces of string and thread, I placed a
loop of fine string, weighing 1-04 gr. (67-4 mg.) on a
terminal sub-petiole: in 6 hrs. 40 m. a curvature could
be seen; in 24 hrs. the petiole formed an open ring round
the string ; in 48 hrs. the ring had almost closed on the
string, and in 72 hrs. seized it so firmly, that some
force was necessary for its withdrawal. A loop weighing
‘52 of a grain (33-7 mg.) caused in 14 hrs. a lateral sub-
petiole just perceptibly to curve, and in 24 hrs. it
moved through ninety degrees. These observations were
made during the summer: the following were made
in the spring, when the petioles apparently are more
sensitive :—A loop of thread, weighing one-eighth of a
grain (801 mg.), produced no effect on the lateral sub-
petioles, but placed on a terminal one, caused it, after
24 hrs., to curve moderately ; the curvature, though the
loop remained suspended, was after 48 hrs. diminished,
but never disappeared; showing that the petiole had
become partially accustomed to the insufficient stimulus.
This experiment was twice repeated with nearly the
same result. Lastly, a loop of thread, weighing only
one-sixteenth of a grain (4°05 mg.) was twice gently
placed by a forceps on a terminal sub-petiole (the
plant being, of course, in a still and closed room), and
this weight certainly caused a flexure, which very

Crap. IL. CLEMATIS. 59

slowly increased until the petiole moved through nearly
ninety degrees: beyond this it did not move; nor did
the petiole, the loop remaining suspended, ever become
perfectly straight again.

When we consider, on the one hand, the thickness
and stiffness of the petioles, and, on the other hand,
the thinness and softness of fine cotton thread, and
what an extremely small weight one-sixteenth of a
grain (4:05 mg.) is, these facts are remarkable. But
T have reason to believe that even a less weight excites
curvature when pressing over a broader surface than
that acted on by a thread. Having noticed that
the end of a suspended string which accidentally
touched a petiole, caused it to bend, I took two
pieces of thin twine, 10 inches in length (weighing
1:64 gr.), and, tying them to a stick, let them hang as
nearly perpendicularly downwards as their thinness
and flexuous form, after being stretched, would per-
mit; I then quietly placed their ends so as just
to rest on two petioles, and these certainly became
curved in 36 hrs. One of the ends touched the angle
between a terminal and lateral sub-petiole, and it was
in 48 hours caught between them as by a forceps. In
these cases the pressure, though spread over a wider
surface than that touched by the cotton thread, must
have been excessively slight.

Clematis vitalba—The plants were in pots and not
healthy, so that I dare not trust my observations, which
indicate much similarity in habits with C.flammula. I
mention this species only because I have seen many

60 LEAF-CLIMBERS. Cuap. IL.

proofs that the petioles in a state of nature are excited
to movement by very slight pressure. For instance,
I have found them embracing thin withered blades
of grass, the soft young leaves of a maple, and the
flower-peduncles of the quaking-grass or Briza. The
latter are about as thick as the hair of a man’s
beard, but they were completely surrounded and clasped.
The petioles of a leaf, so young that none of the leaflets
were expanded, had partially seized a twig. Those of
almost all the old leaves, even when unattached to any
object, are much convoluted; but this is owing to their
having come, whilst young, into contact during several
hours with some object subsequently removed. With
none of the above-described species, cultivated in pots
and carefully observed, was there any permanent
bending of the petioles without the stimulus of contact.
In winter, the blades of the leaves of C. vitalba drop
off; but the petioles (as was observed by Mohl)
remain attached to the branches, sometimes during
two seasons; and, being convoluted, they curiously
resemble true tendrils, such as those possessed by
the allied genus Naravelia. The petioles which have
clasped some object become much more stiff, hard, and
polished than those which have failed in this their
proper function.

TropmoLum.—I observed T. tricolorum, T. azwrewm,
T. pentaphyllum, T. peregrinum, T. elegans, T. tuberosum,
and a dwarf variety of, as I believe, T. minus.

Tropxolum tricolorum, var. grandiflorwum—The
flexible shoots, which first rise from the tubers, are

Cuap. IL. TROPZOLUM. 61

as thin as fine twine. One such shoot revolved in a
course opposed to the sun, at an average rate, judging
from three revolutions, of 1 hr. 23 m.; but no doubt
the direction of the revolving movement is variable.
When the plants have grown tall and are branched,
all the many lateral shoots revolve. The stem, whilst
young, twines regularly round a thin vertical stick,
and in one case I counted eight spiral turns in the
same direction; but when grown older, the stem often
runs straight up for a space, and, being arrested by
the clasping petioles, makes one or two spires in a
reversed direction. Until the plant grows to a height
of two or three feet, requiring about a month from the
time when the first shoot appears above ground, no
true leaves are produced, but, in their place, filaments
coloured like the stem. The extremities of these
filaments are pointed, a little’ flattened, and furrowed
on the upper surface. They never become developed
into leaves. As the plant grows in height new fila-
ments are produced with slightly enlarged tips; then
others, bearing on each side of the enlarged medial tip
a rudimentary segment of a leaf; soon other segments
. appear, and at last a perfect leaf is formed, with seven
deep segments. So that on the same plant we may see
every step, from tendril-like clasping filaments to perfect
Jeaves with clasping petioles. After the plant has grown
to a considerable height, and is secured to its support
by the petioles of the true leaves, the clasping fila-
ments on the lower part of the stem wither and drop
off; so that they perform only a temporary service.

62 LEAF-CLIMBERS. Cuar. IL

These filaments or rudimentary leaves, as well as
the petioles of the perfect leaves, whilst young, are
highly sensitive on all sides to a touch. The slightest
rub caused them to curve towards the rubbed side in
about three minutes, and one bent itself into a ring
in six minutes; they subsequently became straight.
When, however, they have once completely clasped a
stick, if this is removed, they do not straighten them-
selves. The most remarkable fact, and one which I have
observed in no-other species of the genus, is that the
filaments and the petioles of the young leaves, if they
catch no object, after standing for some days in their
original position, spontaneously and slowly oscillate a
little from side to side, and then move towards the
stem and clasp it. They likewise often become, after
a time, in some degree spirally. contracted. They
therefore fully deserve to be called tendrils, as they
are used for climbing, are sensitive to a touch, move
spontaneously, and ultimately contract into a spire,
though an imperfect one. The present species would
have been classed amongst the tendril-bearers, had not
these characters been confined to early youth. During
maturity it is a true leaf-climber.

Tropxolum azureum.—An upper internode made four
revolutions, following the sun, at an average rate of
lhr. 47m. The stem twined spirally round a
support in the same irregular manner as that of the
last species. Rudimentary leaves or filaments do not
exist. The petioles of the young leaves are very
sensitive: a single light rub with a twig caused one

Cuap, IL TROPOLUM. 63

to move perceptibly in 5m, and another in 6m.
The former became bent at right angles in 15 min., and
became straight again in between 5 hrs. and 6 hrs. A
loop of thread weighing 1th of a grain caused another
petiole to curve.

Tropxolum pentaphyllum—tThis species has not the
power of spirally twining, which seems due, not so much
to a want of flexibility in the stem, as to continual
interference from the clasping petioles. An upper inter-
node made three revolutions, following the sun, at an
average rate of 1 hr. 46 m. The main purpose of
the revolving movement in all the species of Tro-
pxolum manifestly is to bring the petioles into contact
with some supporting object. The petiole of a young
leaf, after a slight rub, became curved in 6 m.; another,
on a cold day, in 20m., and others in from 8m.
tol10m. ‘heir curvature usually increased greatly in
from 15m. to 20 m., and they became straight again in
between 5 hrs. and 6 hrs., but on one occasion in 8 hrs.
When a petiole has fairly clasped a stick, it is not able,
on the removal of the stick, to straighten itself. The
free upper part of one, the base of which had already
clasped a stick, still retained the power of movement. A
loop of thread weighing }th of a grain caused a petiole
to curve; but the stimulus was not sufficient, the loop
remaining suspended, to cause a permanent flexure. If
a much heavier loop be placed in the angle between
the petiole and the stem, it produces no effect ; whereas
we have seen with Clematis montana that the angle
between the stem and petiole is sensitive.

64 LEAF-CLIMBERS. Cuap. I

Tropxolum peregrinum.—tThe first-formed internodes
of a young plant did not revolve, resembling in this
respect those of a twining plant. In an older plant
the four upper internodes made three irregular re-
volutions, in a course opposed to the sun, at an average
rate of 1 hr. 48min. It is remarkable that the
average rate of revolution (taken, however, but from
few observations) is very nearly the same in this and
the two last species, namely, 1 hr. 47m., 1 hr. 46m.,
and 1hr.48 m. The present species cannot twine
spirally, which seems mainly due to the rigidity
of the stem. Ina very young plant, which did not
revolve, the petioles were not sensitive. In older
plants the petioles of quite young leaves, and of leaves
as much as an inch and a quarter in diameter, are
sensitive. A moderate rub caused one to curve in
10 m., and others in 20 m. They became straight
again in between 5 hrs. 45 m. and 8 hrs. Petioles
which have naturally come into contact with a stick,
sometimes take two turns round it. After they have
clasped a support, they become rigid and hard. They
are less sensitive to a weight than in the previous
species; for loops of string weighing ‘82 of a grain
(53°14 mg.), did not cause any curvature, but a loop
of double this weight (1°64 gr.) acted.

Tropzxolum elegans.—I did not make many obser-
vations on this species. The short and stiff internodes
revolve irregularly, describing small oval figures.
One oval was completed in 3 hrs. A young petiole,
when rubbed, became slightly curved in 17 m.; and

Cuar. IL j TROPZOLUM. 65

afterwards much more so. It was nearly straight again
in 8 hrs.

Tropxolum tuberosum.—On a plant nine inches in
height, the internodes did not move at all; but on
an older plant they moved irregularly and made
small imperfect ovals. These movements could be
detected only by being traced on a bell-glass placed
over the plant. Sometimes the shoots stood still for
hours; during some days they moved only in one
direction in a crooked line; on other days they made
small irregular spires or circles, one being completed
in about 4 hrs. The extreme points reached by the
apex of the shoot were only about one or one and a half
inches asunder ; yet this slight movement brought the
petioles into contact with some closely surrounding
twigs, which were then clasped. With the lessened power
of spontaneously revolving, compared with that of the
previous species, the sensitiveness of the petioles is
also diminished. These, when rubbed a few times,
did not become curved until half an hour had elapsed ;
the curvature increased during the next two hours,
and then very slowly decreased ; so that they some-
times required 24 hrs. to become straight again.
Extremely young leaves have active petioles; one
with the lamina only 15 of an inch in diameter, that
is, about a twentieth of the full size, firmly clasped
a thin twig. But leaves grown to a quarter of their
full size can likewise act.

Tropxolum minus (?).—The internodes of a variety

named “ dwarf crimson Nasturtium” did not revolve,
4

66 LEAF-CLIMBERS. Cuap. IL

but moved in a rather irregular course during the
day to the light, and from the light at night. The
petioles, when well rubbed, showed no power of curv-
ing; nor could I see that they ever clasped any
neighbouring object. We have seen in this genus
a gradation from species such as T. éricolorum, which
have extremely sensitive petioles, and internodes which
rapidly revolve and spirally twine up a support, to
other species such as T. elegans and T. tuberosum, the
petioles of which are much less sensitive, and the in-
ternodes of which have very feeble revolving powers
and cannot spirally twine round a support, to this last
species, which has entirely lost or never acquired these
faculties. From the general character of the genus,
the loss of power seems the more probable alternative.

In the present species, in 7’. elegans, and probably in
others, the flower-peduncle, as soon as the seed-capsule
begins to swell, spontaneously bends abruptly down-
wards and becomes somewhat convoluted. If a stick
stands in the way, it is to a certain extent clasped ; but,
as far as I have been able to observe, this clasping
movement is independent of the stimulus from contact.

ANTIRRHINEZ.—In this tribe (Lindley) of the
Scrophulariacee, at least four of the seven included
genera have leaf-climbing species.

Maurandia Barelayana.—A thin, slightly bowed
shoot made two revolutions, following the sun, each in
3 hrs. 17 min.; on the previous day this same shoot
revolved in an opposite direction. The shoots do not
twine spiraliy, but climb excellently by the aid cf

Cua. II. MAURANDIA. 67

their young and sensitive petioles. These petioles,
when lightly rubbed, move after a considerable interval
of time, and subsequently become straight again. A
loop of thread weighing ith of a grain caused them to
bend. .

Maurandia semperflorens—This freely growing
species climbs exactly like the last, by the aid of its
sensitive petioles. A young internode made two
circles, each in 1 hr. 46 min.; so that it moved almost
twice as rapidly as the last species. The internodes
are not in the least sensitive to a touch or pressure. J
mention this because they are sensitive in a closely allied
genus, namely, Lophospermum. The present species is
unique in one respect. Mohl asserts (p. 45) that “the
flower-peduncles, as well as the petioles, wind like
tendrils;” but he classes as tendrils such objects
as the spiral flower-stalks of the Vallisneria. This
remark, and the fact of the flower-peduncles being
decidedly flexuous, led me carefully to examine
them. They never act as true tendrils; I repeatedly
placed thin sticks in contact with young and old
peduncles, and I allowed nine vigorous plants to
grow through an entangled mass of branches; but
in no one instance did they bend round any object.
It is indeed in the highest degree improbable that
this should occur, for they are generally developed on
branches which have already securely clasped a
support by the petioles of their leaves; and when
borne on a free depending branch, they are not
produced by the terminal portion of the internode

68 LEAF-CLIMBERS. Cuap, IL

which alone has the power of revolving; so that they
could be brought only by accident into contact with
any neighbouring object. Nevertheless (and this is
the remarkable fact) the flower-peduncles, whilst
young, exhibit feeble revolving powers, and are slightly
sensitive to a touch. Having selected some stems
which had firmly clasped a stick by their petioles,
and having placed a bell-glass over them, I traced
the movements of the young flower-peduncles. The
tracing generally formed a short and extremely irre-
gular line, with little loops in its course. A young
peduncle 14 inch in length was carefully observed
during a whole day, and it made four and a half
narrow, vertical, irregular, and short ellipses—each
at an average rate of about 2 hrs. 25 m. An ad-
joining peduncle described during the same time
similar, though fewer, ellipses. As the plant had
occupied for some time exactly the same position,
these movements could not be attributed to any change
in the action of the light. Peduncles, old enough for
the coloured petals to be just visible, do not move.
With respect to irritability,* I rubbed two young
peduncles (14 inch in length) a few times very lightly
with a thin twig; one was rubbed on the upper, and
the other on the lower side, and they became in
between 4 hrs. and -5 hrs. distinctly bowed towards

* It appears from A. Kerner’s when they are rubbed or shaken:
interesting observations, that the Die Schutzmittel des Pollens.
flower-peduncles ofalargenumber 1873, p. 34.
of plants are irritable, and bend

Cuar. II. MAURANDIA. 69

these sides; in 24 hrs. subsequently, they straightened
themselves. Next day they were rubbed on the
opposite sides, and they became perceptibly curved
towards these sides. Two other and younger pe-
duncles (three-fourths of an inch in length) were
lightly rubbed on their adjoining sides, and they be-
came so much curved towards one another, that the
arcs of the bows stood at nearly right angles to their
previous direction ; and this was the greatest movement
seen by me. Subsequently they straightened them-
selves. Other peduncles, so young as to be only
three-tenths of an inch in length, became curved when
rubbed. On the other hand, peduncles above 14 inch
in length required to be rubbed two or three times,
and then became only just perceptibly bowed. Loops
of thread suspended on the peduncles produced no
effect; loops of string, however, weighing ‘82 and 1:64
of a grain sometimes caused a slight curvature; but
they were never closely clasped, as were the far lighter
loops of thread by the petioles.

In the nine vigorous plants observed by me, it is
certain that neither the slight spontaneous movements
nor the slight sensitiveness of the flower-peduncles
aided the plants in climbing. If any member of the
Scrophulariacee had possessed tendrils produced by
the modification of flower-peduncles, I should have
thought that this species of Mawrandia had perhaps
retained a useless or rudimentary vestige of a former
habit ; but this view cannot be maintained. We may
suspect that, owing to the principle of correlation,

70 LEAF-CLIMBERS, Cuar. IL

the power of movement has been transferred to the
flower-peduncles from the young internodes, and sensi-
tiveness from the young petioles. But to whatever
cause these capacities are due, the case is interest-
ing; for, by a little increase in power through natural
selection, they might easily have been rendered as
useful to the plant in climbing, as are the flower-
peduncles (hereafter to be described) of Vitis or
Cardiospermum.

Rhodochiton volubile——A long flexible shoot swept a
large circle, following the sun, in 5 hrs. 30 m.; and, as
the day became warmer, a second circle was completed
in 4 hrs. 10m. The shoots sometimes make a whole
or a half spire round a vertical stick, they then run
‘straight up for a space, and afterwards turn spirally in
an opposite direction. The petioles of very young
leaves about one-tenth of their full size, are highly
sensitive, and bend towards the side which is touched;
but they do not move quickly. One was perceptibly
curved in 1 hr. 10 m., after being lightly rubbed, and
became considerably curved in 5 hrs. 40 m.; some
others were scarcely curved in 5 hrs. 30 m.,, but dis-
tinctly so in 6 hrs. 30 m. A curvature was perceptible
in one petiole in between 4 hrs. 30 m. and 5 hrs,
after the suspension of a little loop of string. A
loop of fine cotton thread, weighing one sixteenth of a
grain (4:05 mg.), not only caused a petiole slowly to
bend, but was ultimately so firmly clasped that it
could be withdrawn only by some little force. The
petioles, when coming into contact with a stick, take

Duar. IL LOPHOSPERMUM, 71

either a complete or half a turn round it, and ultimately
increase much in thickness. They do not possess the
power of spontaneously revolving.

Lophospermum scandens, var. purpwreum.— Some
long, moderately thin internodes made four revolu-
tions at an average rate of 3 hrs. 15m. The course
pursued was very irregular, namely, an extremely
narrow ellipse, a large circle, an irregular spire or a
zigzag line, and sometimes the apex stood still. The
young petioles, when brought by the revolyimg move-
ment into contact with sticks, clasped them, and soon
increased considerably in thickness. But they are not
quite so sensitive to a weight as those of the Rhodochi-
ton, for loops of thread weighing one-eighth of a grain
did not always cause them to bend.

This plant presents a case not observed by me in
any other leaf-climber or twiner,* namely, that the
young internodes of the stem are sensitive to a
touch. When a petiole of this species clasps a stick,
it draws the base of the internode against it; and then
the internode itself bends towards the stick, which is
caught between the stem and the petiole as by a pair
of pincers. The internode afterwards straightens itself,
excepting the part in actual contact with the stick.
Young internodes alone are sensitive, and these are
sensitive on all sides along their whole length. I made

* I have already referred to the Vries (ibid. p. 322) is sensitive to
case of the twining stem of Cus- a touch like a tendril.
cuta, which, according to H. de

72 LEAF-CLIMBERS. Cuar. IT.

fifteen trials by twice or thrice lightly rubbing with a
thin twig several internodes; and in about 2 hrs., but
in one case in 3 hrs., all were bent: they became
straight again in about 4 hrs. afterwards. An inter-
node, which was rubbed as often as six or seven times,
became just perceptibly curved in 1 hr. 15 m.,, and
in 3 hrs. the curvature increased much; it became
straight again in the course of the succeeding night.
I rubbed some internodes one day on one side, and
the next day either on the opposite side or at right
angles to the first side; and the curvature was always
towards the rubbed side.

According to Palm (p. 63), the petioles of Linaria
cirrhosa and, to a limited degree, those of L. elatine
have the power of clasping a support.

SoLanacea.—Solanwm jasminoides.—Some of the
species in this large genus are twiners ; but the present
species is a true leaf-climber. A long, nearly upright
shoot made four revolutions, moving against the sun,
very regularly at an average rate of 3 hrs. 26m. The
shoots, however, sometimes stood still. It is con-
sidered a greenhouse plant ; but when kept there, the
petioles took several days to clasp a stick: in the
hothouse a stick was clasped in 7 hrs. In the green-
house a petiole was not affected by a loop of string,
suspended during several days and weighing 2}
grains (163 mg.); but in the hothouse one was made
to curve by a loop weighing 1-64 gr. (106-27 mg.); and,
on the removal of the string, it became straight again.
Another petiole was not at all acted on by a loop

Cuar, II. SOLANUM. 713

weighing only ‘82 of a grain (53:14 mg.) We have
seen that the petioles of some other leaf-climbing plants
are affected by one-thirteenth of this latter weight. In
this species, and in no other leaf-climber seen by me,
a full-grown leaf is capable of clasping a stick; but in
the greenhouse the’ movement was so extraordinarily

Fig. 3.
Solanum jasminoides, with one of its petioles clasping a stick.

slow that the act required several weeks; on each
succeeding week it was clear that the petiole had
become more and more curved, until at last it firmly
clasped the stick.

The flexible petiole of a half or a quarter grown
leaf which has clasped an object for three or four
days increases much in thickness, and after several
weeks becomes so wonderfully hard and rigid that it

14 LEAF-CLIMBERS. Cuap. II.

can hardly be removed from its support. On com-
paring a tain transverse slice of such a petiole with one
from an older leaf growing close beneath, which had not
clasped anything, its diameter was found to be fully
doubled, and its structure greatly changed. In two
other petioles similarly compared, and here represented,
the increase in diameter was not quite so great. In
the section of the petiole in its ordinary state (A),
we see a semilunar band of cellular tissue (not

= !

Fig. 4.
Solanum jasminoides,

A. Section of a petiole in its ordinary state.
B. Section of a petiole some weeks after it had clasped a stick, as shown in fig 3.

well shown in the woodcut) differing slightly in
appearance from that outside it, and including three
closely approximate groups of dark vessels. Near
the upper surface of the petiole, beneath two exterior
ridges, there are two other small circular groups of
vessels. In the section of the petiole (B) which had
clasped during several weeks a stick, the two exterior
ridges have beccme much less prominent, and the twc
groups of woody vessels beneath them much increased
in diameter. The semilunar band has been converted
into a complete ring of very hard, white, woody

Cuar. IL. SOLANUM. 75

tissue, with lines radiating from the centre. The
three groups of vessels, which, though near together,
were before distinct, are now completely blended.
The upper part of this ring of woody vessels, formed
by the prolongation of the horns of the original semi-
lunar band, is narrower than the lower part, and
slightly less compact. This petiole after clasping the
stick had actually become thicker than the stem
from which it arose; and this was chiefly due to the
increased thickness of the ring of wood. This ring
presented, both in a transverse and longitudinal
section, a closely similar structure to that of the
stem. It is a singular morphological fact that
the petiole should thus acquire a structure almost
identically the same with that of the axis; and it
is a still more singular physiological fact that so great
a change should have been induced by the mere act
of clasping a support.*

FumariacemZ.—Fumaria officinalis—It could not
have been anticipated that so lowly a plant as this
Fumaria should have been a climber. It climbs by
the aid of the main and lateral petioles of its com-
pound leaves; and even the much-flattened terminal

* Dr. Maxwell Mastersinforms surfaces. In accordance with this

me that in almost all petioles
which are cylindrical, such as
those bearing peltate leaves, the
woody vessels form a closed ring;
semilunar bands of vessels being
confined to petioles which are
channelled along their upper

statement, it may be observed
that the enlarged and clasped
petiole of the Solanum, with its
closed ring of woody vessels, has
become more eylindrical than it
was in its original unclasped
condition.

76 LEAF-CLIMBER<. Cuap. I.

portion of the petiole can seize a support. I have
seen a substance as soft as a withered blade of grass
caught. Petioles which have clasped any object
ultimately become rather thicker and more cylindri-
cal. On lightly rubbing several petioles with a twig,
they became perceptibly curved in 1hr. 15m, and
subsequently straightened themselves. A stick gently
placed in the angle between two sub-petioles excited
them to move, and was almost clasped in 9 hrs. A
loop of thread, weighing one-eighth of a grain, caused,
after 12 hrs. and before 20 hrs. had elapsed, a consider-
able curvature ; but it was never fairly clasped by the
petiole. The young internodes are in continual move-
ment, which is considerable in extent, but very irregu-
lar; a zigzag line, or a spire crossing itself, or a figure
of 8 being formed. The course during 12 hrs., when
traced on a bell-glass, apparently represented about
four ellipses. The leaves themselves likewise move
spontaneously, the main petioles curving themselves
in accordance with the movements of the internodes;
so that when the latter moved to one side, the petioles
moved to the same side, then, becoming straight,
reversed their curvature. The petioles, however,
do not move over a wide space, as could be seen when
a shoot was securely tied to a stick. The leaf in this
case followed an irregular course, like that made by
the internodes.
Adlumia cirrhosa,—I raised some plants late in the
summer; they formed very fine leaves, but threw
up no central stem. The first-formed leaves were not

Cuar. II. ADLUMIA. 77

sensitive; some of the later ones were so, but only
towards their extremities, which were thus enabled to
clasp sticks. This could be of no service to the plant,
as these leaves rose from the ground; but it showed
what the future character of the plant would have
been, had it grown tall enough to climb. The tip
of one of these basal leaves, whilst young, described
in lhr. 36m. a narrow ellipse, open at one end, and
exactly three inches in length; a second ellipse was
broader, more irregular, and shorter, viz, only 24
inches in length, and was completed in 2hrs. 2m.
From the analogy of Fumaria and Corydalis, I have no
doubt that the internodes of Adlumia have the power
of revolving.

Corydalis claviculata.—This plant is interesting
from being in a condition so exactly intermediate
between a leaf-climber and a tendril-bearer, that it
might have been described under either head; but,
for reasons hereafter assigned, it has been classed
amongst tendril-bearers.

Besides the plants already described, Bignoniu
unguis and its close allies, though aided by tendrils,
have clasping petioles. According to Mohl (p. 40),
Cocculus Japonicus (one of the Menispermacee) and a
fern, the Ophtoglossum Japonicum (p. 39), climb by
their leaf-stalks.

We now come to a small section of plants which
climb by means of the produced midribs or tips of
their leaves.

78 LEAF-CLIMBERS. Cuar, IL.

Liniacra.—Gloriosa Plantii—The stem of a half-
grown plant continually moved, generally describ-
ing an irregular spire, but sometimes oval figures
with the longer axes directed in different lines. It
either followed the sun, or moved in an opposite
course, and sometimes stood still before reversing its
direction. One oval was completed in 3 hrs. 40 m.; of
two horseshoe-shaped figures, one was completed in
4hrs. 35m. and the other in 3 hrs. The shoots, in their
movements, reached points between four and five
inches asunder. The young leaves, when first de-
veloped, stand up nearly vertically; but by the
growth of the axis, and by the spontaneous bending
down of the terminal half of the leaf, they soon
become much inclined, aud ultimately horizontal.
The end of the leaf forms a narrow, ribbon-like,
thickened projection, which at first is nearly straight,
but by the time the leaf gets into an inclined position,
the end bends downwards into a well-formed hook.
This hook is now strong and rigid enough to catch
any object, and, when caught, to anchor the plant and
stop the revolving movement. Its inner surface is
sensitive, but not in nearly so high a degree as that
of the many before-described petioles; for a loop of
string, weighing 1-64 grain, produced no effect.
When the hook has caught a thin twig or even a
rigid fibre, the point may be perceived in from 1 hr. to
3hrs. to have curled a little inwards; and, under
favourable circumstances, it curls round and perma-
nently seizes an object in from 8 hrs. to 10 hrs.

re

Cuar. IT. GLORIOSA, 19

The hook when first formed, before the leaf has
bent downwards, is but little sensitive. If it catches
hold of nothing, it remains open and sensitive for
a long time; ultimately the extremity spontaneously
and slowly curls inwards, and makes a button-like,
flat, spiral coil at the end of the leaf. One leaf
was watched, and the hook remained open for thirty-
three days; but during the last week the tip had
curled so much inwards that only a very thin twig
could have been inserted within it. As soon as the
tip has curled so much inwards that the hook is con-
verted into a ring, its sensibility is lost ; but as long as
it remains open some sensibility 1s retained.

Whilst the plant was only about six inches in
height, the leaves, four or five in number, were
broader than those subsequently produced ; their soft
and but little-attenuated tips were not sensitive,
and did not form hooks; nor did the stem then revolve.
At this early period of growth, the plant can support
itself; its climbing powers are not required, and
consequently are not developed. So again, the leaves
on the summit of a full-grown flowering plant, which
would not require to climb any higher, were not sensi-
tive and could not clasp a stick. We thus see how
perfect is the economy of nature.

ComMMELYNACEE.—Flagellaria Indica.—From dried
specimens it is manifest that this plant climbs exactly
like the Gloriosa. A young plant 12 inches in height,
and bearing fifteen leaves, had not a single leaf as yet
produced into a hook or tendril-like filament; nor did

80 LEAF-CLIMBERS. Cnar, IL

the stem revolve. Hence this plant acquires its
climbing powers later in life than does the Gloriosa
lily. According to Mohl (p. 41), Uvularia (Melan-
thacez) also climbs like Gloriosa.

These three last-named genera are Monocotyledons;
but there is one Dicotyledon, namely Nepenthes, which
is ranked by Mohl (p. 41) amongst tendril-bearers;
and I hear from Dr. Hooker that most of the species
climb well at Kew. This is effected by the stalk or
midrib between the leaf and the pitcher coiling round
any support. The twisted part becomes thicker; but
I observed in Mr. Veitch’s hothouse that the stalk
often takes a turn when not in contact with any
object, and that this twisted part is likewise thickened.
Two vigorous young plants of N. levis and N. distilla-
toria, in my hothouse, whilst less than a foot in
height, showed no sensitiveness in their leaves, and
had no power of climbing. But when N. levis had
grown to a height of 16 inches, there were signs of
these powers. The young leaves when first formed
stand upright, but soon become inclined; at this
period they terminate in a stalk or filament, with the
pitcher at the extremity hardly at all developed.
The leaves now exhibited slight spontaneous move-
ments; and when the terminal filaments came into
contact with a stick, they slowly bent round and
firmly seized it. But owing to the subsequent
growth of the leaf, this filament became after a time
quite slack, though still remaining firmly coiled
round the stick. Hence it would appear that the

Cnar. 11, LEAF-CLIMBERS. 8l

chief use of the coiling, at least whilst the plant is
young, is to support the pitcher with its load of
secreted fluid.

Summary on Leaf-climbers—Plants belonging to
eight families are known to have clasping petioles, and
plants belonging to four families climb by the tips of
their leaves. In all the species observed by me,
with one exception, the young internodes revolve more
or less regularly, in some cases as regularly as those
of a twining plant. They revolve at various rates,
in most cases rather rapidly. Some few can ascend
by spirally twining round a support. Differently from
most twiners, there is a strong tendency in the same
shoot to revolve first in one and then in an opposite
direction. The object gained by the revolving move-
ment is to bring the petioles or the tips of the leaves
into contact with surrounding objects; and without this
aid the plant would be much less successful in climb-
ing. With rare exceptions, the petioles are sensitive
only whilst young. They are sensitive on all sides,
but in different degrees in different plants; and in
some species of Clematis the several parts of the same
petiole differ much in sensitiveness. The hooked
tips of the leaves of the Gloriosa are sensitive only on
their inner or inferior surfaces. The petioles are sen-
sitive to a touch and to excessively slight continued
pressure, even from a loop of soft thread weighing
only the one-sixteenth of a grain (4:05 mg.); and
there is reason to believe that the rather thick and

82 LEAF-CLIMBERS. Cuap. IL

stiff petioles of Clematis flammula are sensitive to even
much less weight if spread over a wide surface. The
petioles always bend towards the side which is pressed
or touched, at different rates in different species,
sometimes within a few minutes, but generally after
a much longer period. After temporary contact with
any object, the petiole continues to bend for 4 con-
siderable time ; afterwards it slowly becomes straight
again, and can then re-act. A petiole excited by an
extremely slight weight sometimes bends a little, and
then becomes accustomed to the stimulus, and either
bends no more or becomes straight again, the weight
still remaining suspended. Petioles which have clasped
an object for some little time cannot recover their
original position. After remaining clasped for two or
three days, they generally increase much in thickness
either throughout their whole diameter or on one side
alone; they subsequently become stronger and more
woody, sometimes to a wonderful degree ; and in some
cases they acquire an internal structure like that of the
stem or axis.

The young internodes of the Lophospermum as well
as the petioles are sensitive to a touch, and by their
combined movement seize an object. The flower-
peduncles of the Maurandia semperflorens revolve
spontaneously and are sensitive to a touch, yet are not
used for climbing. The leaves of at least two, and
probably of most, of the species of Clematis, of Fumaria
and Adlumia, spontaneously curve from side to side,
like the internodes, and are thus better adapted to

Cxar. II. LEAF-CLIMBERS. 83

seize distant objects. The petioles of the perfect
leaves of Tropxolum tricolorum, as well as the tendril-
like filaments of the plants whilst young, ultimately
move towards the stem or the supporting stick, which
they then clasp. These petioles and filaments also
show some tendency to contract spirally. The tips of
the uncaught leaves of the Gloriosa, as they grow old,
contract into a flat spire or helix. These several facts
are interesting in relation to true tendrils.

With leaf climbers, as with twining plants, the first
internodes which rise from the ground do not, at least
in the cases observed by me, spontaneously revolve ;
nor are the petioles or tips of the first-formed leaves
sensitive. In certain species of Clematis, the large size
of the leaves, together with their habit of revolving,
and the extreme sensitiveness of their petioles, appear
to render the revolying movement of the internodes
superfluous; and this latter power has consequently
become much enfeebled. In certain species of Tro-
pzolum, both the spontaneous movements of the inter-
nodes and the sensitiveness of the petioles have become
much enfeebled, and in one species have been com-
pletely lost.

CHAPTER III.

Trnpril-BEaRERs,

Nature of tendrils—Bicnon1acez, various species of, and their different
modes of climbing—Tendrils which avoid the light and creep
into crevices—Development of adhesive discs—Excellent adapta-
tions for seizing different kinds of supports—PoLzmoniacka—
Cobza scandens, much branched and hooked tendrils, their manner
of action—Lecuminosa—Comrosirm—Smitacrm—Smilax aspera,
its inefficient tendrils—Fumaniacea—Corydalis claviculata, its
state intermediate between that of a leaf-climber and a tendril-

bearer.

By tendrils I mean filamentary organs, sensitive to
contact and used exclusively for climbing. By this
definition, spines, hooks and rootlets, all of which are
used for climbing, are excluded. True tendrils are
formed by the modification of leaves with their petioles,
of flower-peduncles, branches,* and perhaps stipules.

* Never having had the oppor-
tunity of examining tendrils
produced by the modification of
branches, I spoke doubtfully about
them in this essay when ori-
ginally published. But since
then Fritz Miiller has described
(Journal of Linn. Soe. vol. ix. p.
344) many striking casesin South
Brazil. In speaking of plants
which climb by the aid of their
branches, more or less modified,
he states that the following stages
of development can be traced:

Q1.) Plants supporting themselves
simply by their branches stretched
out at right angles—for example,
Chiococca, (2) Plants clasping a
support with their unmodified
branches, as with Securidaca,
(3.) Plants climbing by the ex-
tremities of their branches which
appear like tendrils, as is the case
according to Endlicher with
Helinus. (4.) Plants with ther
branches much modified and
temporarily converted into ten-
drils, but which may be again

Cuar. IIL. TENDRIL-BEARERS. 85

Mohl, who includes under the name of tendrils various
organs having a similar external appearance, classes
them according to their homological nature, as being
modified leaves, flower-peduncles, &c. This would be
an excellent scheme; but I observe that botanists are
by no means unanimous on the homological nature of
certain tendrils. Consequently I will describe tendril-
bearing plants by natural families, following Lindley’s
classification ; and this will in most cases keep those of
the same nature together. The species to be described
belong to ten families, and will be given in the
following order :—Bignoniacex, Polemoniacex, Legu-
minose, Composite, Smilacex, Fumariacer, Cucurbitacer,

Vitacex, Sapindacex, Passifloracex.*

transformed into branches, as with
certain Papilionaceous plants.
(5.) Plants with their branches
forming true tendrils, and used
exclusively for climbing—as with
Strychnos and Caulotretus. Even
the unmodified branches become
much thickened when they wind
round a support. I may add that
Mr. Thwaites sent me from Ceylon
a specimen of an Acacia which
had climbed up the trunk of a
rather large tree, by the aid of
tendril-like, curved or convoluted
branchlets, arrested in their
growth and furnished with sharp
recurved. hooks,

* As far as I can make out, the
history of our knowledge of
tendrils is as follows:—We have
seen that Palm and von Moh}
observed about the same time the

singular phenomenun of the spon-
taneous revolving movement of
twining-plants. Palm (p. 58), I
presume, observed likewise the
revolving movement of tendrils;
but I do not feel sure of this, for
he says very little on the subject.
Dutrochet fully described this
movement of the tendiil in the
common pea. Mohl first discover-
ed that tendrils are sensitive to
contact; but from some cause,
probably from observing too old
tendrils, he was not aware how
sensitive they were, and thought
that prolonged pressure was neces-
sary to excite their movement.
Professor Asa Gray, in a paper
already quoted, first noticed the
extreme sensitiveness and rapidity
of the movements of the tendrils
of certain Cucurbitaceous plants.

86 TENDRIL-BEALRERS, Cuar. TL.

Bienonrace#.—This family contains many tendril-
bearers, some twiners, and some root-climbers. The
tendrils always consist of modified leaves. Nine species
of Bignonia, selected by hazard, are here described,
in order to show what diversity of structure and
action there may be within the same genus, and to
show what remarkable powers some tendrils possess,
The species, taken together, afford connecting links

Fig. 5.
Bignonta,
Unnamed species from Kew.

between twiners, leaf-climbers, tendril-bearers, and root-
climbers.

Bignonia (an unnamed species from Kew, closely
allied to B. unguis, but with smaller and rather broader
leaves).—A young shoot from a cut-down plant made
three revolutions against the sun, at an average rate of
2 hrs. 6m. The stem is thin and flexible; it twined
round a slender vertical stick, ascending from left to
right, as perfectly and as regularly as any true twining-
plant. When thus ascending, it makes no use of its
tendrils or petioles; but when it twined round a

Cuap. IIL BIGNONIACE:, 87

rather thick stick, and its petioles were brought into
contact with it, these curved round the stick, showing
that they have some degree of irritability. The
petioles also exhibit a slight degree of spontaneous
movement; for in one case they certainly described
minute, irregular, vertical ellipses. The tendrils ap-
parently curve themselves spontaneously to the same
side with the petioles; but from various causes, it was
difficult to observe the movement of either the tendrils
or petioles, in this and the two following species.
The tendrils are so closely similar in all respects to
those of B. unguis, that one description will suffice.
Bignonia unguis——The young shoots revolve, but
less regularly and less quickly than those of the last
species. The stem twines imperfectly round a vertical
stick, sometimes reversing its direction, in the same
manner as described in so many leaf-climbers; and
this plant though possessing tendrils, climbs to a
certain extent like a leaf-climber. Each leaf consists
of a petiole bearing a pair of leaflets, and terminates
in a tendril, which is formed by the modification of
three leaflets, and closely resembles that above figured
(fig. 5). But it is a little larger, and in a young plant
was about half an inch in length. It is curiously like
the leg and foot of a small bird, with the hind toe cut
off. The straight leg or tarsus is longer than the three
toes, which are of equal length, and diverging, lie in
the same plane. The toes terminate in sharp, hard
claws, much curved downwards, like those on a bird’s
foot. The petiole of the leaf is sensitive to contact:

88 TENDRIL-BEARERS. Cuar. OL

even a small loop of thread suspended for two days
caused it to bend upwards; but the sub-petioles of
the two lateral leaflets are not sensitive. The whole
tendril, namely, the tarsus and the three toes,
are likewise sensitive to contact, especially on their
under surfaces. When a shoot grows in the midst of
thin branches, the tendrils are soon brought by the
revolving movement of the internodes into contact
with them; and then one toe of the tendril or more,
commonly all three, bend, and after several hours seize
fast hold of the twigs, like a bird when perched. If
the tarsus of the tendril comes into contact with a
twig, it goes on slowly bending, until the whole foot
is carried quite round, and the toes pass on each side
of the tarsus and seize it. In like manner, if the petiole
comes into contact with a twig, it bends round, carry-
ing the tendril, which then seizes its own petiole or
that of the opposite leaf. The petioles move spon-
taneously, and thus, when a shoot attempts to twine
round an upright stick, those on both sides after a time
come into contact with it, and are excited to bend.
Ultimately the two petioles clasp the stick in opposite
directions, and the foot-like tendrils, seizing on each
other or on their own petioles, fasten the stem to the
support with surprising security. The tendrils are
thus brought into action, if the stem twines round a
thin vertical stick; and in this respect the present
species differs from the last. Both species use their
tendrils in the same manner when passing through a
thicket. This plant is one of the most efficient climbers

Cuar. III. BIGNONIACEA. 89

which I have observed ; and it probably could ascend
a polished stem incessantly tossed by heavy storms.
To show how impértant vigorous health is for the
action of all the parts, I may mention that when I
first examined a plant which was growing moderately
well, though not vigorously, I concluded that the
tendrils acted only like the hooks on a bramble, and
that it was the most feeble and inefficient of all
climbers !

Bignonia Tweedyana.—This species is closely allied
to the last, and behaves in the same manner; but
perhaps twines rather better round a vertical stick.
On the same plant, one branch twined in one direction
and another in an opposite direction. The internodes
in one case made two circles, each in 2 hrs. 33m. I
was enabled to observe the spontaneous movements of
the petioles better in this than in the two preceding
species: one petiole described three small vertical
ellipses in the course of 11 hrs. whilst another
moved in an irregular spire, Some little time after
a stem has twined round an upright stick, and is
securely fastened to it by the clasping petioles and
tendrils, it emits aérial roots from the bases of its
leaves; and these roots curve partly round and adhere
to the stick. This species of Bignonia, therefore, com-
bines four different methods of climbing generally
characteristic of distinct plants, namely, twining, leaf-
climbing, tendril-climbing, and root-climbing.

In the three foregoing species, when the foot-like

tendril has caught an object, it continues to grow
5

90 TENDRIL-BEARERS, Czar. II.

and thicken, and ultimately becomes wonderfully
strong, in the same manner as the petioles of leaf-
climbers. If the tendril catches nothing, it first
slowly bends downwards, and then its power of clasping
is lost. Very soon afterwards it disarticulates itself
from the petiole, and drops off like a leaf in autumn,
I have seen this process of disarticulation in no other
tendrils, for these, when they fail to catch an object,
merely wither away.

Bignonia venusta.—The tendrils differ considerably
from those of the previous species. The lower part,
or tarsus, is four times as long as the three toes; these
are of equal length and diverge equally, but do not
lie in the same plane; their tips are bluntly hooked,
and the whole tendril makes an excellent grapnel. The
tarsus is sensitive on all sides; but the three toes are
sensitive only on their outer surfaces. The sensitive-
ness is not much developed ; for a slight rubbing with
a twig did not cause the tarsus or the toes to become
curved until an hour had elapsed, and then only
in a slight degree. Subsequently they straightened
themselves. Both the tarsus and toes can seize well
hold of sticks. If the stem is secured, the tendrils are
seen spontaneously to sweep large ellipses; the two
opposite tendrils moving independently of one another.
I have no doubt, from the analogy of the two following
allied species, that the petioles also move spontaneously ;
but they are not irritable like those of B. wngwis and
B. Tweedyana. The young internodes sweep large
circles, one being completed in 2 hrs. 15 m. and

Cuap. IL. BIGNONIACEA. 91

a second in 2 hrs.55m. By these combined move-
ments of the internodes, petioles, and grapnel-like
tendrils, the latter are soon brought into contact with
surrounding: objects. When a shoot stands near an
upright stick, it twines regularly and spirally round
it. As it ascends, it seizes the stick with one of its
tendrils, and, if the stick be thin, the right- and left-
hand tendrils are alternately used. This alternation
follows from the stem necessarily taking one twist
round its own axis for each completed circle.

The tendrils contract spirally a short time after
catching any object ; those which catch nothing merely
bend slowly downwards. But the whole subject of
the spiral contraction of tendrils will be discussed
after all the tendril-bearing species have been de-
scribed.

Bignonia littoralis—The young internodes revolve
in large ellipses. An internode bearing immature
tendrils made two revolutions, each in 3 hrs. 50 m.;
but when grown older with the tendrils mature, it
made two ellipses, each at the rate of 2 hrs. 44 m.
This species, unlike the preceding, is incapable of
twining round a stick: this does not appear to be
due to any want of flexibility in the internodes or
to the action of the tendrils, and certainly not to
any want of the revolving power; nor can I account
for the fact. Nevertheless the plant readily ascends
a thin upright stick by seizing a point above with its
two opposite tendrils, which then contract spirally. If
the tendrils seize nothing, they do not become spiral,

92 TENDRIL-BEARERS. Cuar. III.

The species last described, ascended a vertical stick
by twining spirally and by seizing it alternately with
its opposite tendrils, like a sailor pulling himself up
a rope, hand over hand ; the present species pulls itself
up, like a sailor seizing with both hands together a
rope above his head.

The tendrils are similar in structure to those of the
last species. They continue growing for some time,
even after they have clasped an object. When fully
grown, though borne by a young plant, they are 9 inches
in length. The three divergent toes are shorter re-
latively to the tarsus than in the former species; they
are blunt at their tips and but slightly hooked; they
are not quite equal in length, the middle one being
rather longer than the others. Their outer surfaces
are highly sensitive; for when lightly rubbed with
a twig, they became perceptibly curved in 4 m. and
greatly curved in 7m. In 7 hrs. they became straight
again and were ready to re-act. The tarsus, for the
space of one inch close to the toes, is sensitive, but
in a rather less degree than the toes; for the latter,
after a slight rubbing, became curved in about half the
time. Even the middle part of the tarsus is sensitive
to prolonged contact, as soon as the tendril has arrived
at maturity. After it has grown old, the sensitiveness
is confined to the toes, and these are only able to curl
very slowly round a stick. A tendril is perfectly ready
to act, as soon as the three toes have diverged, and
at this period their outer surfaces first Lecome irritable.
The irritability spreads but little from one part when

Cuapr. IIL BIGNONIACE, 93

excited to another: thus, when a stick was caught by
the part immediately beneath the three toes, these
seldom clasped it, but remained sticking straight out.

The tendrils revolve spontaneously. The movement
begins before the tendril is converted into a three-
pronged grapnel by the divergence of the toes, and
before any part has become sensitive; so that the
revolving movement is useless at this early period.
The movement is, also, now slow, two ellipses being
completed conjointly in 24 hrs. 18 m. A mature ten-
dril made an ellipse in 6 hrs.; so that it moved much
more slowly than the internodes. The ellipses which
were swept, both in a vertical and horizontal plane,
were of large size. The petioles are not in the least
sensitive, but revolve like the tendrils. We thus see
that the young internodes, the petioles, and the ten-
drils all continue revolving together, but at different
rates. The movements of the tendrils which rise
opposite one another are quite independent. Hence,
when the whole shoot is allowed freely to revolve,
nothing can be more intricate than the course followed
by the extremity of each tendril. A wide space is
thus irregularly searched for some object to be
grasped.

One other curious point remains to be mentioned.
In the course of a few days after the toes have closely
clasped a stick, their blunt extremities become de-
veloped, though not invariably, into irregular disc-
like balls which have the power of adhering firmly to
the wood. As similiar cellular outgrowths will be

94 TENDRIL-BEARERS. Cuar. IIL

fully described under B. capreolata, I will here say
nothing more about them.

“Bignonia equinoctialis, var. Chamberlaynit—The
internodes, the elongated non-sensitive petioles, and
the tendrils all revolve. The stem does not twine,
but ascends a vertical stick in the same manner as
the last species. The tendrils also resemble those of
the last species, but are shorter; the three toes are
more unequal in length, the two outer ones being
about one-third shorter and rather thinner than the
middle toe; but they vary in this respect. They
.terminate in small hard points; and what is important,
cellular adhesive discs are not developed. The re-
duced size of two of the toes as well as their lessened
sensitiveness, seem to indicate a tendency to abortion ;
and on one of my plants the first-formed tendrils were
sometimes simple, that is, were not divided into three
toes. We are thus naturally led to the three eee
species with undivided tendrils :—

Bignonia speciosa.—The young shoots revolve i irregu-
larly, making narrow ellipses, spires or circles, at rates
varying from 3 hrs. 30 m. to 4 hrs. 40 m.; but they
show no tendency to twine. Whilst the plant is
young and does not require a support, tendrils are
not developed. Those borne by a moderately young
plant were five inches in length. They revolve spon-
taneously, as do the short and non-sensitive petioles.
When rubbed, they slowly bend to the rubbed side
and subsequently straighten themselves ; but they are
not highly sensitive. There is something strange in

Cuap. IIL. BIGNONIACEA. 95

their behaviour: I repeatedly placed close to them,
thick and thin, rough and smooth sticks and posts, as
well as string suspended vertically, but none of these
objects were well seized. After clasping an upright
stick, they repeatedly loosed it again, and often would
not seize it at all, or their extremities did not coil
closely round. I have observed hundreds of tendrils
belonging to various Cucurbitaceous, Passifioraceous,
and Leguminous plants, and never saw one behave in
this manner. When, however, my plant had grown
to a height of eight or nine feet, the tendrils acted
much better. They now seized a thin, upright stick
horizontally, that is, at a point on their own level, and
not some way up the stick as in the case of all the
previous species. Nevertheless, the non-twining stem
was enabled by this means to ascend the stick.

The extremity of the tendril is almost straight and
sharp. The whole terminal portion exhibits a singular
habit, which in an animal would be called an instinct ;
for it continually searches for any little crevice or hole
into which to insert itself. I had two young plants;
and, after having observed this habit, I placed near
them posts, which had been bored by beetles, or had
become fissured by drying. The tendrils, by their
own movement and by that of the internodes, slowly
travelled over the surface of the wood, and when the
apex came to a hole or fissure it inserted itself; in
order to effect this the extremity for a length of half
or quarter of an inch, would often bend itself at right
angles to the basal part. I have watched this process

96 TENDRIL-BEARERS. Cuap. IIL.

between twenty and thirty times. The same tendril
would frequently withdraw from one hole and insert
its point into a second hole. I have also seen a
tendril keep its point, in one case for 20 hrs. and in
another for 36 hrs., in a minute hole, and then with-
draw it. Whilst the point is thus temporarily inserted,
the opposite tendril goes on revolving.

The whole length of a tendril often fits itself closely
to any surface of wood with which it has come into
contact ; and I have observed one bent at right angles,
from having entered a wide and deep fissure, with its
apex abruptly re-bent and inserted into a minute
lateral hole. After a tendril has clasped a stick, it
contracts spirally ; if it remains unattached it hangs
straight downwards. If it has merely adapted itself to
the inequalities of a thick post, though it has clasped
nothing, or if it has inserted its apex into some little
fissure, this stimulus suffices to induce spiral contrac-
tion; but the contraction always draws the tendril
away from the post. So that in every case these
movements, which seem so nicely adapted for some
purpose, were useless. On one occasion, however,
the tip became permanently jammed into a narrow
fissure. I fully expected, from the analogy of B.
eapreolata and B. littoralis, that the tips would have
been developed into adhesive discs; but I could
never detect even a trace of this process. There
is therefore at present something unintelligible about
the habits of this plant.

Bignonia picta—This species closely resembles the

Cuap. LIL BIGNONIACER, 97
last in the structure and movements of its tendrils. I
also casually examined a fine growing plant of the
allied B. Lindleyi, and this apparently behaved in all
respects in the same manner.

Bignonia capreolata—We now come to a species
having tendrils of a different type; but first for the
internodes. A young shoot made three large revolu-
tions, following the sun, at an average rate of 2 hrs. 23 m.
The stem is thin and flexible, and I have seen one
make four regular spiral turns round a thin upright
stick, ascending of course from right to left, and
therefore in a reversed direction compared with the
before described species. Afterwards, from the inter-
ference of the tendrils, it ascended either straight up
the stick or in an irregular spire. The tendrils are
in some respects highly remarkable. In a young
plant they were about 24 inches in length and much
branched, the five chief branches apparently repre-
senting two pairs of leaflets and a terminal one. Each
branch is, however, bifid or more commonly trifid towards
the extremity, with the points blunt yet distinctly
hooked. A tendril bends to any side which is lightly
rubbed, and subsequently becomes straight again ;
but a loop of thread weighing 3th of a grain produced
no effect. On two occasions the terminal branches
became slightly curved in 10 m. after they had touched
astick; andin 30 m. the tips were curled quite round
it. The basal part is less sensitive. The tendrils re-
volved in an apparently capricious manner, sometimes
very slightly or not at all; at other times they

98 TENDRIL-BEARERS. Cuap. IDL

described large regular ellipses. I could detect no
spontaneous movement in the petioles of the leaves,
Whilst the tendrils are revolving more or less
regularly, another remarkable movement takes place,
namely, a slow inclination from the light towards
the darkest side of the house. I repeatedly changed
the position of my plants, and some little time after
the revolving movement had ceased, the successively
formed tendrils always ended by pointing to the
darkest side. When I placed a thick post near a
tendril, between it and the light, the tendril pointed
in that direction. In two instances a pair of leaves
stood so that one of the two tendrils was directed
towards the light and the other to the darkest side of
the house; the latter did not move, but the opposite
one bent itself first upwards and then right over its
fellow, so that the two became parallel, one above the
other, both pointing to the dark: I then turned the
plant half round; and the tendril which had turned
over recovered its original position, and the opposite
one which had not before moved, now turned over to
the dark side. Lastly, on another plant, three pairs
‘of tendrils were produced at the same time by three
shoots, and all happened to be differently directed: I
placed the pot in a box open only on one side, and
obliquely facing the light; in two days. all six ten-
drils pointed with unerring truth to the darkest corner
of the box, though to do this each had to bend in a
different manner. Six wind-vanes could not have
more truly shown the direction of the wind, than did

Cuap. IIL, BIGNONIACEZ. 99

these branched tendrils the course of the stream of
light which entered the box. I left these tendrils
undisturbed for above 24 hrs., and then turned the
pot half round; but they had now lost their power of
movement, and could not any longer avoid the light.

When a tendril has not succeeded in clasping a
support, either through its own revolving movement or
that of the shoot, or by turning towards any object
which intercepts the light, it bends vertically down-
wards and then towards its own stem, which it seizes
together with the supporting stick, if there be one.
A little aid is thus given in keeping the stem secure.
If the tendril seizes nothing, it does not contract
spirally, but soon withers away and drops off. If it
seizes an object, all the branches contract spirally.

I have stated that after a tendril has come into
contact with a stick, it bends round it in about half
an hour; but I repeatedly observed, as in the case
of B. speciosa and its allies, that it often again loosed
the stick ; sometimes seizing and loosing the same stick
three or four times. Knowing that the tendrils avoided
the light, I gave them a glass tube blackened within,
and a well-blackened zinc plate: the branches curled
round the tube and abruptly bent themselves round
the edges of the zine plate; but they soon recoiled
from these objects with what I can only call disgust,
and straightened themselves. I then placed a post
with extremely rugged bark close to a pair of tendrils;
twice they touched it for an hour or two, and twice
they withdrew ; at last one of the hooked extremities

100 TENDRIL-BEAREERS. Cuar. IIL

curled round and firmly seized an excessively minute
projecting point of bark, and then the other branches
spread themselves out, following with accuracy every
inequality of the surface. I afterwards placed near
the plant a post without bark but much fissured, and
the points of the tendrils crawled into all the crevices
in a beautiful manner. To my surprise, I observed
that the tips of the immature tendrils, with the
branches not yet fully separated, likewise crawled
just like roots into the minutest crevices. In two
or three days after the tips had thus crawled into
the crevices, or after their hooked ends had seized
minute points, the final process, now to be described,
commenced.

This process I discovered by having accidentally
left a piece of wool near a tendril; and this led me to
bind a quantity of flax, moss, and wool loosely round
sticks, and to place them near tendrils. The wool must
not be dyed, for these tendrils are excessively sensitive
to some poisons. The hooked points soon caught hold
of the fibres, even loosely floating fibres, and now there
was no recoiling; on the contrary, the excitement
caused the hooks to penetrate the fibrous mass and
to curl inwards, so that each hook caught firmly one
or two fibres, or a small bundle of them. The tips
and the inner surfaces of the hooks now began to swell,
and in two or three days were visibly enlarged. After
afew more days the hooks were converted into w hitish,
irregular balls, rather above the 3th of an inch (1:27
mm.) in diameter, formed of coarse cellular tissue,

Cxap. IIL BIGNONIACEA. 101

which sometimes wholly enveloped and concealed the
hooks themselves. The surfaces of these balls secrete
some viscid resinous matter, to which the fibres of the
flax, &c., adhere. When a fibre has become fastened
to the surface, the cellular tissue does not grow
directly beneath it, but continues to grow closely on
each side; so that when several adjoining fibres,
though excessively thin, were caught, so many crests
of cellular matter, each not as thick as a human hair,
grew up between them, and these, arching over on
both sides, adhered firmly together. As the whole
surface of the ball continues to grow, fresh fibres
adhere and are afterwards enveloped; so that I have
seen a little ball with between fifty and sixty fibres
of flax crossing it at various angles and all embedded
more or less deeply. Every gradation in the process
could be followed—some fibres merely sticking to
the surface, others lying in more or less deep furrows,
or deeply embedded, or passing through the very
centre of the cellular ball. The embedded fibres are
so closely clasped that they cannot be withdrawn.
The outgrowing tissue has so strong a tendency to
unite, that two balls produced by distinct tendrils
sometimes unite and grow into a single one.

On one occasion, when a tendril had curled round
a stick, half an inch in diameter, an adhesive disc
was formed; but this does not generally occur in the
case of smooth sticks or posts. If, however, the tip
catches a minute projecting point, the other branches
form discs, especially if they find crevices to crawl

102 TENDRIL-BEARERS. Cuap. II.

into. The tendrils failed to attach themselves to a
brick wall.

I infer from the adherence of the fibres to the dises
or balls, that these secrete some resinous adhesive
matter; and more especially from such fibres becoming
loose if immersed in sulphuric ether. This fluid like-
wise removes small, brown, glistening points which can
generally be seen on the surfaces of the older discs.
If the hooked extremities of the tendrils do not touch
anything, discs, as far as I have seen, are never
formed ;* but temporary contact during a moderate
time suffices to cause their development. I have seen
eight discs formed on the same tendril. After their
development the tendrils contract spirally, and become
woody and very strong. A tendril in this state sup-
ported nearly seven ounces, and would apparently have
supported a considerably greater weight, had not the
fibres of flax to which the discs were attached yielded.

From the facts now given, we may infer that though
the tendrils of this Bignonia can occasionally adhere
to smooth cylindrical sticks and often to rugged bark,
yet that they are specially adapted to climb trees
clothed with lichens, mosses, or other such productions ;
and I hear from Professor Asa Gray that the Polypodiwm
ineanum abounds on the forest-trees in the districts of

* Fritz Miiller states (ibid. p. object, terminate in smooth shining
848) that in South Brazil the discs. Tiese, however, after ad-
trifid tendrils of Haplolophium, hering to any object, sometimes
(one of the Bignoniacex) without become considerably enlarged.
having come into contact with any

Cnar, HL BIGNONIACEZ. 103

North America where this species of Bignonia grows.
Finally, I may remark how singular a fact it is that
a leaf should be metamorphosed into a branched
organ which turns from the light, and which can
by its extremities either crawl like roots into crevices,
or seize hold of minute projecting points, these ex-
tremities afterwards forming cellular outgrowths which
secrete an adhesive cement, and then envelop by their
continued growth the finest fibres.

Eccremocarpus scaber (Bignoniacex).—Plants, though
growing pretty well in my green-house, showed no
spontaneous movements in their shoots or tendrils;
but when removed to the hot-house, the young inter-
nodes revolved at rates varying from 3 hrs. 15 m. to
1 hr.13m. One large circle was swept at this latter
unusually quick rate; but generally the circles or
ellipses were small, and sometimes the course pursued
was quite irregular. An internode, after making several
revolutions, sometimes stood still for 12 hrs. or 18 hrs.,
and then recommencedrevolving. Suchstrongly marked
interruptions in the movements of the internodes I
have observed in hardly any other plant.

The leaves bear four leaflets, themselves subdivided,
and terminate in much-branched tendrils. The
main petiole of the leaf, whilst young, moves sponta-
neously, and follows nearly the same irregular course
and at about the same rate as the internodes. The
movement to and from the stem is the most con-
spicuous, and I have seen the chord of a curved petiole
which formed an angle of 59° with the stem, in an

104 TENDRIL-BEARERS. Cuar. Ul

hour afterwards making an angle of 106°. The two
opposite petioles do not move together, and one is
sometimes so much raised as to stand close to the stem,
whilst the other is not far from horizontal. The basal
part of the petiole moves less than the distal part. The
tendrils, besides being carried by the moving petioles
and internodes, themselves move spontaneously ; and
the opposite tendrils occasionally move in opposite
directions. By these combined movements of the
young internodes, petioles, and tendrils, a considerable
space is swept in search of a support.

In young plants the tendrils are about three inches
in length: they bear two lateral and two terminal
branches; and each branch bifurcates twice, with the
tips terminating in blunt double hooks, having both
points directed to the same side. All the branches are
sensitive on all sides; and after being lightly rubbed,
or after coming into contact with a stick, bend in
about 10 m. One which had become curved in 10 m.
after a light rub, continued bending for between 3 hrs.
and 4 hrs. and became straight again in 8 hrs, or
9 hrs. Tendrils, which have caught nothing, ultimately
contract into an irregular spire, as they likewise do,
only much more quickly, after clasping a support. In
both cases the main petiole bearing the leaflets, which
is at first straight and inclined a little upwards,
moves downwards, with the middle part bent abruptly
into a right angle; but this is seen in FE. miniatus
more plainly than in EF. scaber. The tendrils in this
genus act in some respects like those of Bignonia

Cuap, IL. BIGNONIACEZ. 105

capreolata; but the whole does not move from the
light, nor do the hooked tips become enlarged into cel-
lular discs. After the tendrils have come into contact
with a moderately thick cylindrical stick or with
rugged bark, the several branches may be seen slowly
to lift themselves up, change their positions, and
again come into contact with the supporting surface.
The object of these movements is to bring the double
hooks at the extremities of the branches, which natu-
rally face in all directions, into contact with the wood.
I have watched a tendril, half of which had bent itself
at right angles round the sharp corner of a square post,
neatly bring every single hook into contact with both
rectangular surfaces. The appearance suggested the
belief, that though the whole tendril is not sensitive to
light, yet that the tips are so, and that they turn
and twist themselves towards any dark surface. Ulti-
mately the branches arrange themselves very neatly
to all the irregularities of the most rugged bark, so
that they resemble in their irregular course a river
with its branches, as engraved on a map. But when
a tendril has wound round a rather thick stick, the
subsequent spiral contraction generally draws it away
and spoils the neat arrangement. So it is, but not in
quite so marked a manner, when a tendril has spread
itself over a large, nearly flat surface of rugged bark.
We may therefore conclude that these tendrils are not
perfectly adapted to seize moderately thick sticks or
rugged bark. If a thin stick or twig is placed near
a tendril, the terminal branches wind quite round it,

L06 TENDRIL-BEARERS. Cup. LI.

and then seize their own lower branches or the main
stem. The stick is thus firmly, but not neatly,
grasped. What the tendrils are really adapted for,
appears to be such objects as the thin culms of certain
grasses, or the long flexible bristles of a brush, or thin
rigid leaves such as those of the Asparagus, all of
which they seize in an admirable manner. This is
due to the extremities of the branches close to the
little hooks being extremely sensitive to a touch
from the thinnest object, which they consequently
curl round and clasp. When a small brush, for
instance, was placed near a tendril, the tips of each
sub-branch seized one, two, or three of the bristles;
and then the spiral contraction of the several branches
brought all these little parcels close together, so that
thirty or forty bristles were drawn into a single bundle,
which afforded an excellent support.
POLEMONIACEE.— Cobea scandens— This is an
excellently constructed climber. The tendrils on a
fine plant were eleven inches long, with the petiole
bearing two pairs of leaflets, only two and a half
inches in length. They revolve more rapidly and
vigorously than those of any other tendril-bearer
observed by me, with the exception of one kind of
Passiflora. Three large, nearly circular sweeps, di-
rected against the sun were completed, each in 1 hr.
15 m.; and two other circles in 1 hr. 20 m. and 1 hr.
23 m. Sometimes a tendril travels in a much inclined
position, and sometimes nearly upright. The lower part
moves but little and the petiole not at all; nor dc

Cuar. III. POLEMONIACEZ. 107

the internodes revolve; so that here we have the tendril
alone moving. On the other hand, with most of the
species of Bignonia and the Eecremocarpus, the inter-
nodes, tendrils, and petioles all revolved. The long,
straight, tapering main ste1a of the tendril of the Cobea
bears alternate branches; and each branch is several
times divided, with the finer branches as thin as very
thin bristles and extremely flexible, so that they are
blown about by a breath of air; yet they are strong
and highly elastic. The extremity of each branch is a
little flattened, and terminates in a minute double
(though sometimes single) hook, formed of a hard, trans-
lucent, woody substance, and as sharp as the finest
needle. On a tendril which was eleven inches long I
counted ninety-four of these beautifully constructed
little hooks. They readily catch soft wood, or gloves,
or the skin of the naked hand. With the exception of
these hardened hooks, and of the basal part of the central
stem, every part of every branchlet is highly sensitive
on all sides to a slight touch, and bends in a few
minutes towards the touched side. By lightly rub-
bing several sub-branches on opposite sides, the whole
tendril rapidly assumed an extraordinarily crooked
shape. These movements from contact do not inter-
fere with the ordinary revolving movement. The
branches, after becoming greatly curved from being
touched, straighten themselves at a quicker rate than
in almost any other tendril seen by me, namely, in
between half an hour and an hour. After the tendril
has caught any object, spiral contraction likewise

LO8 TENDRIL-BEARERS. Cuap. IIL,

begins after an unusually short interval of time,
namely, in about twelve hours.

Before the tendril is mature, the terminal branchlets
cohere, and the hooks are curled closely inwards. At
this period no part is sensitive to a touch; but as soon
as the branches diverge and the hooks stand out, full
sensitiveness is acquired. It is a singular circumstance
that immature tendrils revolve at their full velocity
before they become sensitive, but in a useless manner,
as in this state they can catch nothing. This want
of perfect co-adaptation, though only for a short time,
between the structure and the functions of a climbing-
plant is a rare event. A tendril, as soon as it is ready
to act, stands, together with the supporting petiole,
vertically upwards. The leaflets borne by the petiole
are at this time quite small, and the extremity of the
growing stem is bent to one side so as to be out
of the way of the revolving tendril, which sweeps
large circles directly over head. The tendrils thus
revolve in a position well adapted for catching objects
standing above; and by this means the ascent of the
plant is favoured. If no object is caught, the leaf
with its tendril bends downwards and ultimately
assumes a horizontal position. An open space is
thus left for the next succeeding and younger tendril
to stand vertically upwards and to revolve freely.
As soon as an old tendril bends downwards, it loses
all power of movement, and contracts spirally into an
entangled mass. Although the tendrils revolve with
unusual rapidity, the movement lasts for only a short

Cuar. III. POLEMONIACES, 109

time. In a plant placed in the hot-house and grow-

ing vigorously, a tendril revolved for not longer than

36 hours, counting from the period when it first became

sensitive; but during this period it probably made at
least 27 revolutions.

When a revolving tendril strikes against a stick,
the branches quickly bend round and clasp it. The
little hooks here play an important part, as they
prevent the branches from being dragged away by the
rapid revolving movement, before they have had time
to clasp the stick securely. This is especially the case
when only the extremity of a branch has caught
hold of a support. As soon as a tendril has bent
round a smooth stick or a thick rugged post, or has
come into contact with planed wood (for it can adhere
temporarily even to so smooth a surface as this), the
same peculiar movements may be observed as those
described under Bignonia capreolata and Eccremocar-
pus. The branches repeatedly lift themselves up and
down; those which have their hooks already directed
downwards remaining in this position and securing
the tendril, whilst the others twist about until they
succeed in arranging themselves in conformity with
every irregularity of the surface, and in bringing
their hooks into contact with the wood. The use of
the hooks was well shown by giving the tendrils
tubes and slips of glass to catch; for these, though
temporarily seized, were invariably lost, either during
the re-arrangement of the branches or ultimately when
spiral contraction ensued.

110 TENDRIL-BEARERS. Cuap. IL.

The perfect manner in which the branches arranged
themselves, creeping like rootlets over every inequality
of the surface and into any deep crevice, is a pretty
sight; for it is perhaps more effectually performed
by this than by any other species. The action is
certainly more conspicuous, as the upper surfaces of
the main stem, as well as of every branch to the
extreme hooks, are angular and green, whilst the lower
surfaces are rounded and purple. I was led to infer,
as in former cases, that a less amount of light guided
these movements of the branches of the tendrils.
I made many trials with black and white cards and
glass tubes to prove it, but failed from various causes ;
yet these trials countenanced the belief. As a tendril
consists of a leaf split into numerous segments, there is
nothing surprising in all the segments turning their
upper surfaces towards the light, as soon as the tendril
is caught and the revolving movement is arrested.
But this will not account for the whole movement, for
the segments actually bend or curve to the dark side
besides turning round on their axes so that their upper
surfaces may face the light.

When the Cobxa grows in the open air, the wind
must aid the extremely flexible tendrils in seizing a
support, for I found that a mere breath sufficed to cause
the extreme branches to catch hold by their hooks of
twigs, which they could not have reached by the
revolving movement. Jt might have been thought
that a tendril, thus hooked by the extremity ofa single
branch, could not have fairly grasped its support.

Caar. Il. POLEMONIACEA, 111

But several times I watched cases like the following:
a tendril caught a thin stick by the hooks of one of
its two extreme branches; though thus held by the
tip, it still tried to revolve, bowing itself to all sides,
and by this movement the other extreme branch soon
caught the stick. The first branch then loosed itself,
and, arranging its hooks, again caught hold. After a
time, from the continued movement of the tendril,
the hooks of a third branch caught hold. No other
branches, as the tendril then stood, could possibly
have touched the stick. But before long the upper
part of the main stem began to contract into an open
spire. It thus dragged the shoot which bore the
tendril towards the stick; and as the tendril con-
tinually tried to revolve, a fourth branch was brought
into contact. And lastly, from the spiral contraction
travelling down both the main stem and the branches,
all of them, one after another, were ultimately brought
into contact with the stick. They then wound them-
selves round it and round one another, until the whole
tendril was tied together in an inextricable knot.
The tendrils, though at first quite flexible, after
having clasped a support for a time, become more
rigid and stronger than they were at first. Thus the
plant is secured to its support in a perfect manner.
Lecuminosz.—Pisum sativum.—The common pea
was the subject of a valuable memoir by Dutrochet,*
who discovered that the internodes and tendrils

* Comptes Rendus, tom. xvii. 1843, p. 989.

112 TENDRIL-BEARERS. Cuap. Il

revolve in ellipses. The ellipses are generally very
narrow, but sometimes approach to circles. I several
times observed that the longer axis slowly changed its
direction, which is of importance, as the tendril thus
sweeps a wider space. Owing to this change of
direction, and likewise to the movement of the stem
towards the light, the successive irregular ellipses
generally form an irregular spire. I have thought it
worth while to annex a tracing of the course pursued
by the upper internode (the movement of the tendril
being neglected) of a young plant from 8.40 a.m. to 9.15
pM. The course was traced on a hemispherical glass
placed over the plant, and the dots with figures give
the hours of observation; each dot being joined by a
straight line. No doubt all the lines would have been
curvilinear if the course had been observed at much
shorter intervals. The extremity of the petiole, from
which the young tendril arose, was two inches from
the glass, so that if a pencil two inches in length
could have been affixed to the petiole, it would have
traced the annexed figure on the under side of the
glass; but it must be remembered that the figure is
reduced by one-half. Neglecting the first great
sweep towards the light from the figure 1 to 2, the
end of the petiole swept a space 4 inches across in one
direction, and 3 inches in another. As a full-grown
tendril is considerably above two inches in length, and
as the tendril itself bends and revolves in harmony
with the internode, a considerably wider space is swept
than is here represented on a reduced scaJe, Dutrochet

Cuar. III. LEGUMINOSA, 113

observed the completion of an ellipse in 1 hr. 20 m.;

and I saw one completed in 1 hr.30 m. The direction

followed is variable, either with or against the sun.
Dutrochet asserts that the petioles of the leaves

Side of room with window.
Fig. 6.
Diagram showing the movement of athe Hd internode of the common Pea, traced on
pherical glass, and to paper; reduced one-half in size. (Aug. 1st.)
No. a. M. No. BH. M. No. iH, M.
lee + 8 46 A.M, 9. - 155 Pa [16. . 2. . 6 25 PM.
2.62. -100 4 0 225 MW... . 550,
3... -llo, ll ~ 3 0,4 Ww... . 62,
4... -1137 , 12 330 » 19. 2... 70
5. 2. « 2.12 7 Pw 13. » 348 , 20... . 74 y
G6. a 1230 ,, 14 . 440 , 21... . 830,
Te ew ew eh TOY 15 5 5 yy 22. » 91 ,
Be. we 130 ,,

spontaneously revolve, as well as the young inter-

nodes and tendrils; but he does not say that he
6

114 TENDRIL-BEARERS. Cnar. Ill,

secured the internodes; when this was done, I could
never detect any movement in the petiole, except to
and from the light.

The tendrils, on the other hand, when the internodes
and petioles are secured, describe irregular spires or
regular ellipses, exactly like those made by the inter-
nodes. A young tendril, only 1} inch in length,
revolved. Dutrochet has shown that when a plant is
placed in a room, so that the light enters laterally, the
internodes travel much quicker to the light than from
it: on the other hand, he asserts that the tendril itself
moves from the light towards the dark side of the
room. With due deference to this great observer, I
think he was mistaken, owing to his not having
secured the internodes. I took a young plant with
highly sensitive tendrils, and tied the petiole so that
the tendril alone could move; it completed a perfect
ellipse in 1 hr. 30 m.; I then turned the plant partly
round, but this made no change in the direction
of the succeeding ellipse. The next day I watched a
plant similarly secured until the tendril (which was
highly sensitive) made an ellipse in a line exactly to
and from the light; the movement was so great that -
the tendril at the two ends of its elliptical course
bent itself a little beneath the horizon, thus travelling
more than 180 degrees; but the curvature was fully
as great towards the light as towards the dark side
of the room. I believe Dutrochet was misled by not
having secured the internodes, and by having observed
a plant of which the internodes and tendrils no longer

Cuar, III, LEGUMINOSZ. 115

curved in harmony together, owing to inequality of
age.

Dutrochet made no observations on the sensitiveness
of the tendrils. These, whilst young and about an inch
in length with the leaflets on the petiole only partially
expanded, are highly sensitive; a single light touch
with a twig on the inferior or concave surface near the
tip caused‘them to bend quickly, as did occasionally
a loop of thread weighing one-seventh of a grain
(9°25 mg.). The upper or convex surface is barely or
not at all sensitive. Tendrils, after bending from a
touch, straighten themselves in about two hours, and
are then ready to act again. As soon as they begin
to_ grow old, the extremities of their two or three pairs
of branches become hooked, and they then appear to
form an excellent grappling instrument; but this is
not the case. For at this period they have generally
quite lost their sensitiveness ; and when hooked on to
twigs, some were not at all affected, and others required
from 18 hrs. to 24 hrs. before clasping such twigs;
nevertheless, they were able to utilise the last vestige
of irritability owing to their extremities being hooked.
Ultimately the lateral branches contract spirally, but
not the middle or main stem.

Lathyrus aphaca.—This plant is destitute of leaves,
excopt during a very early age, these being replaced
by tendrils, and the leaves themselves by large stipules.
It might therefore have been expected that the ten-
drils would have been highly organized, but this is
not so. They are moderately long, thin, and un-

Li6 TEN DRIL-BEABERS. Cuar. IIL.

branched, with their tips slightly curved. Whilst
young they are sensitive on all sides, but chiefly on
the concave side of the extremity. They have no
spontaneous revolving power, but are at first inclined
upwards at an angle of about 45°, then move into a
horizontal position, and ultimately bend downwards.
The young internodes, on the other hand, revolve in
ellipses, and carry with them the tendrils. -Two
ellipses were completed, each in nearly 5 hrs.; their
longer axes were directed at about an angle of 45°
to the axis of the previously made ellipse.

Lathyrus grandiflorus—The plants observed were
young and not growing vigorously, yet sufficiently so,
I think, for my observations to be trusted. If so, we
have the rare case of neither internodes nor tendrils
revolving. The tendrils of vigorous plants are above
4 inches in length, and are often twice divided into
three branches ; the tips are curved and are sensitive
on their concave sides; the lower part of the central
stem is hardly at all sensitive. Hence this plant
appears to climb simply by its tendrils being brought,
through the growth of the stem, or more efficiently
by the wind, into contact with surrounding objects,
which they then clasp. I may add that the tendrils,
or the internodes, or both, of Vicia sativa revolve.

Composita. — Mutisia clematis.— The immense
family of the Composite is well known to include
very few climbing plants. We have seen in the Table
in the first chapter that Mikania scandens is a re-
gular twiner, and F. Miller informs me that in S

Cap, IIL. COMPOSIT. 117

Brazil there is another species which is a leaf-climber.
Mutisia is the only genus in the family, as far as
I can learn, which bears tendrils: it is therefore
interesting to find that these, though rather less
metamorphosed from their primordial foliar condition
than are most other tendrils, yet display all the
ordinary characteristic movements, both those that
are spontaneous and those which are excited by con-
tact.

The long leaf bears seven or eight alternate leaflets,
and terminates in a tendril which, in a plant of con-
siderable size, was 5 inches in length. It consists
generally of three branches; and these, although
much elongated, evidently represent the petioles and
midribs of three leaflets; for they closely resemble
the same parts in an ordinary leaf, in being rectangular
on the upper surface, furrowed, and edged with green.
Moreover, the green edging of the tendrils of young
plants sometimes expands into a narrow lamina or
blade. Each branch is curved a little downwards, and’
is slightly hooked at the extremity. :

A young upper internode revolved, judging from
three revolutions, at an average rate of 1 hr. 38 m.; it
swept ellipses with the longer axes directed at right
angles to one another; but the plant, apparently,
cannot twine. The petioles and the tendrils are both
in constant movement. But their movement is slower
and much less regularly elliptical than that of the
internodes. They appear to be much affected by the
light, for the whole leaf usually sinks down during the

118 TENDRIL-BEARERS. Cuap. IIL

night and rises during the day, moving, also, during
the day im a crooked course to the west. The tip of
the tendril is highly sensitive on the lower surface ;
and one which was just touched with a twig became
perceptibly curved in 3 m., and another in 5 m.; the
upper surface is not at all sensitive; the sides are
moderately sensitive, so that two branches which were
rubbed on their inner sides converged and crossed each
other. The petiole of the leaf and the lower parts of
the tendril, halfway between the upper leaflet and the
lowest branch, are not sensitive. A tendril after curling
from a touch became straight again in about 6 hrs., and
was ready to re-act; but one that had been so roughly
rubbed as to have coiled into a helix did not become
perfectly straight until after 13 hrs. The tendrils re-
tain their sensibility to an unusually late age; for one
borne by a leaf with five or six fully developed leaves
above, was still active. If a tendril catches nothing,
after a considerable interval of time the tips of the
branches curl a little inwards; but if it clasps some
object, the whole contracts spirally.
SminacezZ.—Smilax aspera, var. maculata.—Aug.
St.-Hilaire* considers that the tendrils, which rise in
pairs from the petiole, are modified lateral leaflets;
but Mohl (p. 41) ranks them as modified stipules.
These tendrils are from 1} to 1} inches in length, are
thin, and have slightly curved, pointed extremities.
They diverge a little from each other, and stand at
first nearly upright. When lightly rubbed on either

* *Lecons de Botanique,’ &c., 1841, p. 170.

Cuap. IIL, SMILACEZ. 119

side, they slowly bend to that side, and subsequently
become straight again. -The back or convex side
when placed in contact with a stick became just per-
ceptibly curved in 1 hr. 20 m., but did not completely

Fig. 7..
Smilax aspera.

surround it until 48 hrs. had elapsed; the concave side
of another became considerably curved in 2 hrs. and
clasped a stick in 5 hrs. As the pairs of tendrils grow
old, one tendril diverges more and more from the
other, and both slowly bend backwards and downwards,
so that after a time they project on the opposite side

120 YENDRIL-BEARERS. Cuap. IIL.

of the stem to that from which they arise. They then
still retain their sensitiveness, and can clasp a support
placed behind the stem. Owing to this power,. the
plant is able to ascend a thin upright stick. Ulti-
mately the two tendrils belonging to the same petiole,
if they do not come into contact with any object,
loosely cross each other behind the stem, as at B, in
fig. 7. This movement of the tendrils towards and
round the stem is, to a certain extent, guided by their
avoidance of the light; for when a plant stood so that
one of the two tendrils was compelled in thus slowly
moving to travel towards the light, and the other from
the light, the latter always moved, as I repeatedly
observed, more quickly than its fellow. The tendrils
do not contract spirally in any case. Their chance
of finding a support depends on the growth of the
plant, on the wind, and on their own slow backward
and downward movement, which, as we have just seen,
is guided, to a certain extent, by the avoidance of the
light ; for neither the internodes nor the tendrils have
any proper revolving movement. From this latter
circumstance, from the slow movements of the tendrils
after contact (though their sensitiveness is retained for
an unusual length of time), from their simple structure
and shortness, this plant is a less perfect climber than
any other tendril-bearing species observed by me. The
plant whilst young and only a few inches in height,
does not produce any tendrils; and considering that
it grows to only about 8 feet in height, that the stem
is zigzag and is furnished, as well as the petioles, with

Cuap. III. FUMARIACES, 121

spines, it is surprising that it should be provided with
tendrils, comparatively inefficient ‘though these are.
The plant might have been left, one would have
thought, to climb by the aid of its spines alone, like
our brambles. As, however, it belongs to a genus,
some of the species of which are furnished with much
longer’ tendrils, we may suspect that it possesses these
organs solely from being descended from progenitors
more highly organized in this respect.
Fumartacea.—Corydalis claviculata.—According to
Mohl (p. 43), the extremities of the branched stem,
as well as the leaves, are converted into tendrils.
In the specimens examined by me all the tendrils were
certainly foliar, and it is hardly credible that the same
plant should produce tendrils of a widely different.
homological nature. Nevertheless, from this state-
ment by Mohl, I have ranked this species amongst the
tendril-bearers; if classed exclusively by its foliar
tendrils, it would be doubtful whether it ought not to
have been placed amongst the leaf-climbers, with its
allies, Fumaria and Adlumia. A large majority of its
so-called tendrils still bear leaflets, though excessively
reduced in size; but some few of them may properly
be designated as -tendiils, for they are completely
destitute of lamine or blades. Consequently, we here
behold a- plant i in an actual state of transition from a leaf-
climber to a tendril-bearer. - Whilst the plant is rather
young; only the outer leaves, but when full-grown all
the leaves, have their extremities converted into more
or less perfect tendrils. I have examined specimens .

{22 TENDRIL-BEARERS, Cuap. II.

from one locality alone, viz. Hampshire; and it is not
improbable that plants growing under different condi-
tions might have their leaves a little more or less
changed into true tendrils.

Whilst the plant is quite young, the first-formed
leaves are not modified in any way, but those next
formed have their terminal leaflets reduced in size,
«od soon all the leaves assume the structure repre-
sented in the following drawing. This leaf bore nine
leaflets; the lower ones being much subdivided. The
terminal portion of the petiole, about 14 inch in
length (above the leaflet f), is thinner and more
elongated than the lower part, and may be considered
as the tendril. The leaflets borne by this part are
greatly reduced in size, being, on an average, about
the tenth of an inch in length and very narrow; one
small leaflet measured one-twelfth of an inch in
length and one-seventy-fifth in breadth (2116 mm. and
‘339 mm.), so that it was almost microscopically minute.
All the reduced leaflets have branching nerves, and
terminate in little spines, like those of the fully de-
veloped leaflets. Every gradation could be traced,
until we come to branchlets (as a and d in the figure)
which show no vestige of a lamina or blade. Occasion-
ally all the terminal branchlets of the petiole are in
this condition, and we then have a true tendril.

The several terminal branches of the petiole bearing
the much reduced leaflets (a, b, ¢, d) are highly
sensitive, for a loop of thread weighing only the one-
sixteenth of a grain (4:05 mg.) caused them to become

Cuar. JIL. FUMARIACEZ. 123

greatly curved in under 4 hrs. When the loop was
removed, the petioles straightened themselves in about
thesametime. The petiole (¢) was rather less sensitive ;
and in another specimen, in which the corresponding

Corydalis claviculata.
Leaf-tendril, of natural size.

petiole bore rather larger leaflets, a loop of thread
weighing one-eighth of a grain did not cause curvature
until 18 hrs, had elapsed. Loops of thread weighing
one-fourth of a grain, left suspended on the lower

.

124 TENDRII-BEARERS. Cuap. IIT.

petioles (f to 2) during several days, produced no
effect. Yet the three petioles f, g, and h were not
quite insensible, for when left in contact with a stick
for a day or two they slowly curled round it. Thus
the sensibility of the petiole gradually diminishes
from the tendril-like extremity to the base. The in-
ternodes of the stem are not at all sensitive, which
makes Mohl’s statement that they are sometimes con-
verted into tendrils the more surprising, not to say
improbable.

The whole leaf, whilst young and sensitive, stands
almost vertically upwards, as we have seen to be the
case with many tendrils. It is in continual move-
‘ment, and one that I observed swept at an average
rate of about 2 hrs. for each revolution, large, though
irregular, ellipses, which were sometimes narrow,
sometimes broad, with their longer axes directed to
different points of the compass. The young inter-
nodes, likewise revolved irregularly in ellipses or
spires; so that by these combined movements a con-
siderable space was swept for a support. If the terminal
and attenuated portion of a petiole fails to seize any
object, it ultimately bends downwards and inwards,
and soon loses all irritability and power of movement.
This bending down differs much in nature from that
which occurs with the extremities of the young leaves
in many species of Clematis; for these, when thus
bent downwards or hooked, first acquire their full
degree of sensitiveness.

Dicentra thalictrifolia.—In this allied plant the

Cuar., LL. FUMARIACEZ. 125

metamorphosis of the terminal leaflets is complete,
and they are converted into perfect tendrils. Whilst
the plant is young, the tendrils appear like modified
branches, and. a distinguished botanist thought that
they were of this nature; but in a full-grown plant
there can be no doubt, as I am assured by Dr. Hooker,
that they are modified leaves. When of full size, they
are above 5 inches in length; they bifurcate twice,
thrice, or even .four times; their extremities are
hooked and blunt. All the branches of the tendrils
are sensitive on all sides, but the basal portion of the
main stem is only slightly so. The terminal branches
when lightly rubbed with a twig became curved in
the course of from 30 m. to 42 m., and straightened
themselves in between 10 hrs. and 20 hrs. A loop
of thread weighing one-eighth of a grain plainly
caused the thinner branches to bend, as did occasion-
ally a loop weighing. one-sixteenth of a grain; but
this latter weight, though left suspended, was not
sufficient to cause a permanent flexure. The whole
leaf with its tendril, as well as the young upper inter-
nodes, revolves vigorously and quickly, though irregu-
larly, and thus sweeps a wide space. The figure traced
on a bell-glass was either an irregular spire or a
zigzag line. The nearest approach to an ellipse was an
elongated figure of 8, with one end a little open, and
this was completed in 1 hr.53 m. During a period
of 6 hrs. 17 m. another shoot made a complex figure,
apparently representing three and a half ellipses.
When the lower part of the petiole bearing the leaflets

126 TENDRIL-BEARERS. Cuar. II.

was securely fastened, the tendril itself described
similar but much smaller figures.

This species climbs well. The tendrils after clasp-
ing a stick become thicker and more rigid; but the
blunt hooks do not turn and adapt themselves to the
supporting surface, as is done in so perfect a manner
by some Bignoniacee and Cobea. The tendrils of
young plants, two or three feet in height, are only
half the length of those borne by the same plant when
grown taller, and they do not contract spirally after
clasping a support, but only become slightly flexuous.
full-sized tendrils, on the other hand, contract spirally,
with the exception of the thick basal portion. Ten-
drils which have caught nothing simply bend down-
wards and inwards, like the extremities of the leaves
of the Corydalis claviculata. But in all cases the
petiole after a time is angularly and abruptly bent
downwards like that of Eccremocarpus.

Car. IV. CUCURBITACE. 127.

CHAPTER IV.

TENDRIL-BEARERS—(continued).

CveursrraceEz—Homologous nature sf the tendrils—Echinocystis lobata,
remarkable movements of the tendrils to avoid seizing the terminal
shoot—Tendrils not excited by contact with another tendril or by
drops of water—Undulatory movement of the extremity of the tendril
—Hanburya, adherent discs—Viraca—Gradation between tho
flower-peduncles and tendrils of the vine—Tendrils of the Virginian
Creeper turn from the light, and, after contact, develop adhesive
discs—SaPinDAcEa —PassIFLORACEZ—Passiflora gracilis — Rapid
revolying movement and sensitiveness of the tendrils—Not sensitive
to the contact of other tendrils or of drops of water—Spiral con-
traction of tendrils—Summary on the nature and action of

tendrils,

Cucursitacez.—The tendrils in this family have
been ranked by competent judges as modified leaves,
stipules, or branches; or as partly a leaf and partly
a branch. De Candolle believes that the tendrils
differ in their homological nature in two of the tribes.*
From facts recently adduced, Mr. Berkeley thinks
that Payer’s view is the most probable, namely, that
the tendril is “a separate portion of the leaf itself ;”
but much may be said in favour of the belief that it
is a modified flower-peduncle.t

* T am indebted to Prof. Oliver
for information on this head. In
the Bulletin de la Société Bota-
nique de France, 1857, there are
numerous discussions on the
nature of the tendrils in this
family,

+ ‘ Gardeners’ Chronicle,’ 1864,
p. 721. From the affinity of the
Cucurbitacez to the Passifloracez,
it might be argued that the
tendrils of the former are modified
flower-peduncles, as is certainly
the case with those of Passion=

i28 TENDRIL-BEARERS. Cuar. IV.

Echinocystis lobata.—Numerous observations were
made on this plant (raised from seed sent me by Prof.
Asa Gray), for the spontaneous revolving movements
of the internodes and tendrils were first observed by
me in this case, and greatly perplexed me. My obser-
vations may now be much condensed. I observed
thirty-five revolutions of the internodes and tendrils ;
the slowest rate was 2 hrs., and the average rate, with
no great fluctuations, 1 hr. 40 m. Sometimes I tied
the internodes, so that the tendrils alone moved; at
other times I cut off the tendrils whilst very young,
so that the internodes revolved by themselves; but
the rate was not thus affected. The course generally
pursued was with the sun, but often in an opposite
direction. Sometimes the movement during a short
time would either stop or be reversed; and this
apparently was due to interference from the light,
as, for instance, when I placed a plant close to a
window. In one instance, an old tendril, which had
nearly ceased revolving, moved in one direction,
whilst a young tendril above moved in an opposite
course. The two uppermost internodes alone revolve;
and as soon as the lower one grows old, only its upper
part continues to move. The ellipses or circles swept
by the summits of the internodes are about three inches
in diameter; whilst those swept by the tips of ‘the

flowers. Mr. R. Holland (Hard- garden, where one of the short
wicke’s ‘ Science-Gossip,’ 1865, p. prickles upon the fruit had
105) states that “a cucumber grown out into a long, curled
grew, afew years ago in my own _ tendril.”

Cuar. IV. CUCURBITACEZ. 129

tendrils, are from 15 to 16 inches in diameter. During
the revolving movement, the internodes become
successively curved to all points of the compass;
in one part of their course they are often inclined,
together with the tendrils, at about 45° to the horizon,
and in another part stand vertically up. There was
something in the appearance of the revolving internodes
which continually gave the false impression that their
movement was due to the weight of the long and
spontaneously revolving tendril ; but, on cutting off the
latter with sharp scissors, the top of the shoot rose only
a little, and went onrevolving. This false appearance
is apparently due to the internodes and tendrils all
curving and moving harmoniously together.

A revolving tendril, though inclined during the
greater part of its course at an angle of about 45° (in
one case of only 37°) above the horizon, stiffened and
straightened itself from tip to base in a certain
part of its course, thus becoming nearly or quite
vertical. I witnessed this repeatedly ; and it occurred
both when the supporting internodes were free and
when they were tied up; but was perhaps most con-
spicuous in the latter case, or when the whole shoot
happened to be much inclined: The tendril forms a
very acute angle with the projecting extremity of the
stem or shoot; and the stiffening always occurred as
the tendril approached, and had to pass over the shoot
in its circular course. If it had not possessed and
exercised this curious power, it would infallibly have
struck against the extremity of the shoot and been

133 TENDRIL-BEARERS. Cuapr. IV.

arrested. As soon as the tendril with its three
branches begins to stiffen itself in this manner and to
rise from an inclined into a vertical position, the
revolving motion becomes more rapid; and as soon
as the tendril has succeeded in passing over the ex-
tremity of the shoot or point of difficulty, its motion,
coinciding with that from its weight, often causes it to
fall into its previously inclined position so quickly,
that the apex could be seen travelling like the minute
hand of a gigantic clock.

The tendrils are thin, from 7 to 9 inches in length,
with a pair of short lateral branches rising not far
from the base. The tip is slightly and permanently
curved, so as to act to a limited extent as a hook. The
concave side of the tip is highly sensitive to a touch;
but not so the convex side, as was likewise observed
to be the case with other species of the family by
Mohl (p. 65). I repeatedly proved this difference by
lightly rubbing four or five times the convex side of
one tendril, and only once or twice the concave side
of another tendril, and the latter alone curled inwards.
In a few hours afterwards, when the tendrils which
had been rubbed on the concave side had straightened
themselves, I reversed the process of rubbing, and
always with the same result. After touching the
concave side, the tip becomes sensibly curved in one or
two minutes; and subsequently, if the touch has been at
all rough, it coils itself into a helix. But the helix
will, after a time, straighten itself, and be again ready
to act. A loop of thin thread only one-sixteenth of

Cuap. IV. CUCURBITACER. 131

a grain in weight caused a temporary flexure. The
lower part was repeatedly rubbed rather roughly, but
no curvature ensued; yet this part is sensitive to pro-
longed pressure, for when it came into contact with a
stick, it would slowly wind round it.

One of my plants bore two shoots near together,
and the tendrils were repeatedly drawn across one
another, but it is a singular fact that they did not
once catch each other. It would appear as if they had
become habituated to contact of this kind, for the
pressure thus caused must have been much greater
than that caused by a loop of soft thread weighing
only the one-sixteenth of a grain. I have, however,
seer several tendrils of Bryonia dioica interlocked, but
they subsequently released one another. The tendrils
of the Echinocystis are also habituated to drops of
water or to rain ; for artificial rain made by violently
flirting a wet brush over them produced not the least
effect.

The revolving movement of a tendril is not stopped
by the curving of its extremity after it has been
touched. When one of the lateral branches has firmly
clasped an object, the middle branch continues to
revolve. When a stem is bent down and secured, so
that the tendril depends but is left free to move, its pre-
vious revolving movement is nearly or quite stopped ;
but it soon begins to bend upwards, and as soon as it
has become horizontal the revolving movement recom-
mences. I tried this four times ; the tendril generally
rose to a horizontal position in an hour or an hour and

132 TENDRIL-BEARERS. Cuar. IV.

a half; but in one case, in which a tendril depended at
an angle of 45° beneath the horizon, the uprising took
two hours; in half an hour afterwards it rose to 23°
above the horizon and then recommenced revolving.
This upward movement is independent of the action of
light, for it occurred twice in the dark, and on another
occasion the light came in on one side alone. The
movement no doubt is guided by opposition to the
force of gravity, as in the case of the ascent of the
plumules of germinating seeds.

A tendril does not long retain its revolving power ;
and as soon as this is lost, it bends downwards and
contracts spirally. After the revolving movement
has ceased, the tip still retains for a short time its
sensitiveness to contact, but this can be of little or no
use to the plant.

Though the tendril is highly flexible, and: though
the extremity travels, under favourable circumstances,
at about the rate of an inch in two minutes and a
quarter, yet its sensitiveness to contact is so great that
it hardly ever fails to seize a thin stick placed in its
path. The following case surprised me much: I placed
a thin, smooth, cylindrical stick (and I repeated the
experiment seven times) so far from a tendril, that
its extremity could only curl half or three-quarters
‘round the: stick; but I always found that the ‘tip
managed in the course of a few hours to curl twice
or even thrice round the stick. I at first thought
that this was due to rapid growth on the outside; but
by coloured points and 1easurements I proved that

Cuar. IV. CUCURBITACES. 133

there had been no sensible increase of length within
the time. When a stick, flat on one side, was
similarly placed, the tip of the tendril could not
curl beyond the flat surface, but coiled itself. into
a helix, which, turning to one side, lay flat on the
little flat surface of wood. In one instance a portion
of tendril three-quarters of an inch in length was thus
dragged on to the flat surface by the coiling in of the
helix. But the tendril thus acquires a very insecure
hold, and generally after a time slips off. In one case
alone the helix subsequently uncoiled itself, and the
tip then passed round and clasped the stick. The
formation of the -helix on the flat side of the stick
apparently shows us that the continued striving of the
tip to curl itself closely inwards gives the force which
drags the tendril round a smooth cylindrical stick.
In this latter case, whilst the tendril was slowly and
quite insensibly crawling onwards, I observed several
times through a lens that the whole surface was not in
close contact with the stick; and I can understand the
onward progress only by supposing that the movement
is slightly undulatory or vermicular, and that the tip
alternately straightens itself a little and then again
curls inwards. It thus drags itself onwards by an
insensibly 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. -However this may be, the fact is
certain that a tendril which has caught a round stick

Lot TENDRIL-BEARESS. Cuar. IV.

with its extreme point, can work itself onwards until
it has passed twice or even thrice round the stick,
and has permanently grasped it.

Hanburya Mexicana.—The young internodes and
tendrils of this anomalous member of the family, revolve
in the same manner and at about the same rate as those
of the Echinocystis, The stem does not twine, but can
ascend an upright stick by the aid of its tendrils.
The concave tip of the tendril is very sensitive; after
it had become rapidly coiled into a ring owing to
a single touch, it straightened itself in 50 m. The
tendril, when in full action, stands vertically up, with
the projecting extremity of the young stem thrown a
little on one side, so as to be out of the way; but the
tendril bears on the inner side, near its base, a short
rigid branch, which projects out at right angles like
a spur, with the terminal half bowed a little down-
wards. Hence, as the main vertical branch revolves,
the spur, from its position and rigidity, cannot pass
over the extremity of the shoot, in the same curious
manner as do the three branches of the tendril of the
Echinocystis, namely, by stiffening themselves at the
proper point. The spur is therefore pressed laterally
against the young stem in one part of the revolving
course, and thus the sweep of the lower part of the main
branch is much restricted. A nice case of co-adaptation
here comes into play: in all the other tendrils observed
by me, the several branches become sensitive at the
same period: had this been the case with the Hanburya,
the inwardly directed, spur-like branch, from being

Cuar. IV. CUCURBITACE. 135

pressed, during the revolving movement, against the
projecting end of the shoot, would infallibly have
seized it in a useless or injurious manner. But the
main branch of the tendril, after revolving for a time
in a vertical position, spontaneously bends downwards ;
and in doing so, raises the spur-like branch, which
itself also curves upwards; so that by these combined
movements it rises above the projecting end of the
shoot, and can now move freely without touching the
shoot; and now it first becomes sensitive.

The tips of both branches, when they come into
contact with a stick, grasp it like any ordinary tendril.
But in the course of a few days, the lower surface.
swells and becomes developed into a cellular layer,
which adapts itself closely to the wood, and firmly
adheres to it. This layer is analogous to the adhesive
discs formed by the extremities of the tendrils of
some species of Bignonia and of Ampelopsis; but
in the Hanburya the layer is developed along the
terminal inner surface, sometimes for a length of
1} inches, and not at the extreme tip. The layer
is white, whilst the tendril is green, and near the
tip it is sometimes thicker than the tendril itself; it
generally spreads a little beyond the sides of the
tendril,,and is fringed with free elongated cells, which
have enlarged globular or retort-shaped heads. This
cellular layer apparently secretes some resinous cement ;
for its adhesion to the wood was not lessened by an
immersion of 24 hrs. in alcohol or water, but was quite
loosened by a similar immersion in ether or turpentine,

136 TEN DRIL-BEARERS. Cuar. IV.

After a tendril has once firmly coiled itself round
a stick, it is difficult to imagine of what use the ad-
hesive cellular layer can be. Owing to the spiral
contraction which svon ensues, the tendrils were never
able to remain, excepting in one instance, in contact
with a thick post or a nearly flat surface ; if they had
quickly become attached by means of the adhesive
layer, this would evidently have been of service to the
plant.

The tendrils of Bryonia dioica, Cucurbita ovifera,
and Cucumis sativa are sensitive and revolve. Whether
the internodes likewise revolve I did not observe. In
Anguria Warscewiczti, the internodes, though thick
and stiff, revolve: in this plant the lower surface of
the tendril, some time after clasping a stick, produces
a coarsely cellular layer or cushion, which adapts itself
closely to the wood, like that formed by the tendril of
the Hanburya ; but it is not in the least adhesive. In
Zanonia Indica, which belongs to a different tribe of
the family, the forked tendrils and the internodes re-
volve in periods between 2 hrs. 8 m. and 3 hrs. 35 m.,
moving against the sun.

Vitacrz.—In this family and in the two following,
namely, the Sapindacez and Passifloraces, the tendrils
are modified flower-peduncles; and are therefore axial
in their nature. In this respect they differ from all
those previously described, with the exception, per-
haps, of the Cucurbitacez. The homological nature,
however, of a tendril seems to make no difference
in its action.

Guay, IV; VITACER. 137

Vitis vinifera—The tendril is thick and of great
length; one from a vine growing out of doors and not
vigorously, was 16 inches long. It consists of a
peduncle (A), bearing two branches which diverge
equally from it. One of the branches (B) has a
scale at its base; it is always, as far as I have seen,
longer than the other and often bifurcates. The
branches when rubbed become curved, and subse-

Fig. 9.

Tendril of the Vine.
A. Peduncle of tendril. C. Shorter branch.
4B, Longer branch, with a scale at its base. D. Petiole of the opposite leaf.

quently straighten themselves. After a tendril has
clasped any object with its extremity, it contracts
spirally; but this does not occur (Palm, p. 56) when

no object has been seized. The tendrils move spon-
7

138 TENDRIL-BEARERS. Crap. IV.

taneously from side to side; and on a very hot day,
one made two elliptical revolutions, at an average rate
of 2hrs.15 m. During these movements a coloured
line, painted along the convex surface, appeared after
a time on one side, then on the concave side, then on
the opposite side, and lastly again on the convex side.
The two branches of the same tendril have independent
movements. After a tendril has spontaneously revolved
for a time, it bends from the light towards the dark:
I do not state this on my own authority, but on that
of Mohl and Dutrochet. Mohl (p. 77) says that in a
vine planted against a wall the tendrils point towards
it, and in a vineyard generally more or less to the
north.

The young internodes revolve spontaneously ; but
the movement is unusualfy slight. A shoot faced a
window, and I traced its course on the glass during
two perfectly calm and hot days. On one of these
‘days it described, in the course of ten hours, a spire,
representing two and a half ellipses. I also placed
a bell-glass over a young Muscat grape in the hot-
house, and it made each day three or four very small
oval revolutions; the shoot moving less than half an
inch from side to side. Had it not made at least three
revolutions whilst the sky was uniformly overcast, I
should have attributed this slight degree of movement
to the varying action of the light. The extremity of
the stem is more or less bent downwards, but it
never reverses its curvature, as so generally occurs
with twining plants.

Cuar. IV. VITACE. 139

Various authors (Palm, p. 55; Mohl, p. 45; Lindley,
&c.) believe that the tendrils of the vine are modified
flower-peduncles. I here give a drawing (fig. 10) of
the ordinary state of a young flower-stalk: it consists

Fig. 10.
Flower-stalk of the Vine.

A. Common Peduncle, C. Sub-Peduncle, bearing the flower-buds,
B, Flower-tendril, with a scale at its base. D. Petiole of the opposite leaf.

of the “common peduncle” (A); of the “ flower-
tendril” (B), which is represented as having caught a
twig; and of the “sub-peduncle” (C) bearing the
flower-buds. The whole moves spontaneously, like a
true tendril, but in a less degree; the movement,

140 TENDRIL-BEARERS, Cuar. IV.

however, is greater when the sub-peduncle (C) does
not bear many flower-buds. The common peduncle
(A) has-not the power of clasping a support, nor has
the corresponding part of a true tendril. The flower-
tendril (B) is always longer than the sub-peduncle (C)
and has a scale at its base; it sometimes bifurcates,
and therefore corresponds in every detail with the
longer scale-bearing branch (B, fig. 9) of the true
tendril. It is, however, inclined backwards from the
sub-peduncle (C), or stands at right angles with it,
and is thus adapted to aid in carrying the future
bunch of grapes. When rubbed, it curves and sub-
sequently straightens itself; and it can, as is shown in
the drawing, securely clasp a support. I have seen
an object as soft as a young vine-leaf caught by
one.

The lower and naked part of the sub-peduncle (C)
‘is likewise slightly sensitive to a rub, and I have seen
it bent round a stick and even partly round a leaf
with which it had come into contact. That the sub-
peduncle has the same nature as the corresponding
branch of an ordinary tendril, is well shown when it
bears only a few flowers; for in this case it becomes
less branched, increases in length, and gains both
in sensitiveness and in the power of spontaneous
movement. I have twice seen sub-peduncles which
bore from thirty to forty flower-buds, and which had
become considerably elongated and were completely
wound round sticks, exactly like true tendrils. The
whole length of another sub-peduncle, bearing only

Cuap, IV. VITACEZ. 141

eleven flower-buds, quickly became curved when
slightly rubbed; but even this scanty number of
flowers rendered the stalk less sensitive than the
other branch, that is, the flower-tendril ; for the latter
after a lighter rub became curved more quickly and
in a greater degree.. I have seen a sub-peduncle
thickly covered with flower-buds, with one of its
higher lateral branchlets bearing from some cause
only two buds; and this one branchlet had become
much elongated and had spontaneously caught hold
of an adjoining twig ; in fact, it formed a little sub-
tendril, The increasing length of the sub-peduncle
(C) with the decreasing number of the flower-buds is a
good instance of the law of compensation. In accord-
ance with this same principle, the true tendril as a whole
is always longer than the flower-stalk; for instance,
on the same plant, the longest flower-stalk (measured
from the base of the common peduncle to the tip of
the flower-tendril)- was 84 inches in length, whilst the
longest tendril was nearly double this length, namely
16 inches.

The gradations from the ordinary state of a flower-
stalk, as represented in the drawing (fig. 10), to
that of a true tendril (fig. 9) are complete. We have
seen that the sub-peduncle (C), whilst still bearing
from thirty to forty flower-buds, sometimes becomes a
little elongated and partially assumes all the characters
of the corresponding branch of a true tendril. From
this ‘state we can trace every stage till we come to
a full-sized perfect tendril, bearing on the branch

142 TENDRIL-BEARERS. Cuar. IV,

which corresponds with the sub-peduncle one single
flower-bud! Hence there can be no doubt that the
tendril is a modified flower-peduncle.

Another kind of gradation well deserves notice.
Flower-tendrils (B, fig. 10) sometimes produce a few
flower-buds. For instance, on a vine growing against
my house, there were thirteen and twenty-two flower-
buds respectively on two flower-tendrils, which still
retained their characteristic qualities of sensitiveness
and spontaneous movement, but in a somewhat lessened
degree. On vines in hothouses, so many flowers are
occasionally produced on the flower-tendrils that a
double bunch of grapes is the result ; and this is techni-
cally called by gardeners a“ cluster.” In this state the
whole bunch of flowers presents scarcely any resem-
blance to a tendril; and, judging from the facts already
given, it would probably possess little power of clasping
a support, or of spontaneous movement. Such fiower-
stalks closely resemble in structure those borne by
Cissus. This genus, belonging to the same family of
the Vitacez, produces well-developed tendrils and
ordinary bunches of flowers ; but there are no gradations
between the two states. Ifthe genus Vitis had been
unknown, the boldest believer in the modification of
species would never have surmised that the same
individual plant, at the same period of growth,
would have yielded every possible gradation between
ordinary flower-stalks for the support of the flowers
and fruit, and tendrils used exclusively for climbing.
But the vine clearly gives us such a case; and it

Cuar. IV. VITACES. 1438

seems to me as striking and curious an instance of
transition as can well be conceived.

Cissus discolor—The young shoots show no more
movement than can be accounted for by daily variations
in the action of the light. The tendrils, however,
revolve with much regularity, following the sun ; and,
in the plants observed by me, swept circles of about
5 inches in diameter. Five circles were completed
in the following times :—4 hrs. 45 m., 4 hrs. 50 m.,
4 hrs. 45 m., 4 hrs. 30 m., and 5 hrs. The same tendril
continues to revolve during three or four days. The
tendrils are from 3} to 5 inches in length. They are
formed of a long foot-stalk, bearing two short branches,
which in old plants again bifurcate. The two branches
are not of quite equal length; and as with the vine,
the longer one has a scale at its base. The tendril
stands vertically upwards; the extremity of the shoot
being bent abruptly downwards, and this position is
probably of service to the plant by allowing the tendril
to revolve freely and vertically.

Both branches of the tendril, whilst young, are
highly sensitive. A touch with a pencil, so gentle as
only just to move a tendril borne at the end of
a long flexible shoot, sufficed to cause it to become
perceptibly curved in four or five minutes. It became
straight again in rather above one hour. A loop of
soft thread weighing one-seventh of a grain (9:25 mg.)
was thrice tried, and each time caused the tendril to
become curved in 80 or 40 m. Half this weight pro-
duced no effect. The long foot-stalk is much less

144 TENDRIL-BEAREBS. Cuae. IV,

sensitive, for a slight rubbing produced no effect, al-
though prolonged contact with a stick caused it to bend.
The two branches are sensitive on all sides, so that they
converge if touched on their inner sides, and diverge
if touched on their outer sides, If a branch be touched
at the same time with equal force on opposite sides,
both sides are equally stimulated and there is no move-
ment. Before examining this plant, I had observed
only tendrils which are sensitive on one side alone,
and these when lightly pressed between the finger and
thumb become curved; but on thus pinching many
times the tendrils of the Cissus no curvature ensued,
and I falsely inferred at first that they were not at all
sensitive.

Cissus antarcticus——The tendrils on a young plant
were thick and straight, with the tips a little curved.
‘When their concave surfaces were rubbed, and it was
necessary to do this with some force, they very slowly
became curved, and subsequently straight again.
They are therefore much less sensitive than those of
the last species; but they made two revolutions, fol-
lowing the sun, rather more rapidly, viz.,in 3 hrs. 30 m.
and 4 hrs. The internodes do not revolve.

Ampelopsis hederacea (Virginian Creeper).—The inter-
nodes apparently do not move more than can be
accounted for by the varying action of the light. The
tendrils are from 4 to 5 inches in length, with the main
stem sending off several lateral branches, which have
their tips curved, as may be seen in the upper figure
(fig. 11). They exhibit no true spontaneous revolving

Cnap. IV. VITACER. 145

movement, but turn, as was long ago observed by
Andrew Knight,* from the light to the dark. I have
seen several tendrils move in less than 24 hours, through
an angle of 180° to the dark side of a case in which
a plant was placed, but the movement is sometimes
much slower. The several lateral branches often move
independently of one another, and sometimes irregu-
larly, without any apparent cause. These tendrils are
less sensitive to a touch than any others observed by
me. By gentle but repeated rubbing with a twig, the
lateral branches, but not the main stem, became in the
course of three or four hours slightly curved; but
they seemed to have hardly any power of again
straightening themselves. The tendrils of a plant which
had crawled over a large. box-tree clasped several of the
branches; but I have repeatedly seen that they will
withdraw themselves after seizing a stick. When they
meet with a flat surface of wood or a wall. (and this
is evidently what they are adapted for), they turn
all their branches towards it, and, spreading them
widely apart, bring their hooked tips laterally into
contact with it. In effecting this, the several branches,
after touching the surface, often rise up, place them-
selves in a new position, and again come down into
contact with it.

In the course of about. two days after a tendril has
arranged its branches so as to press on any surface, the
curved tips swell, become bright red, and form on

* Trans. Phil. Soc. 1812, p, 314.

Cuar. IV

146 TENDRIL-BEARERS.

their under-sides the well-known little discs or cushions
with which they adhere firmly. In one case the tips
were slightly swollen in 38 hrs. after coming into
contact with a brick; in another case they were
considerably swollen in 48 hrs., and in an additional
24 hrs. were firmly attached to a smooth board; and
lastly, the tips of a younger tendril not only swelled
but became attached to a stuccoed wall in 42 hrs.
These adhesive discs resemble, except in colour and
in being larger, those of Bignonia capreolata. When
they were developed in contact with a ball of tow, the
fibres were separately enveloped, but not in so effective
a manner as by B. capreolata. Discs are never de-
veloped, as far as I have seen, without the stimulus of
at least temporary contact with some object.* They
are generally first formed on one side of the curved tip,
the whole of which often becomes so much changed
in appearance, that a line of the original green tissue
can be traced only along the concave surface. When,
however, a tendril has clasped a cylindrical stick, an
irregular rim or disc is sometimes formed along the
inner surface at some little distance from the curved

* Dr. M’Nab remarks (Trans.
Bot. Soc. Edinburgh, vol xi. p.
292) that the tendrils of Amp,

adhere to any surface. The ten-
drils, therefore, of one species of
Ampelopsis require the stimulus

Veitchii bear small globular discs
before they have come into contact
with any object; and I have since
observed the same fact. These
discs, however, increase greatly
in size, if they press against and

of contact for the first development
of their discs, whilst those of
another species do not need any
such stimulus. We have seen an
exactly parallel case with twa
species of Bignoniaccz.

Car. 1V. VITACE. 147

tip; this was also observed (p. 71) by Mobl. The discs
consist of enlarged cells, with smooth projecting hemi-
spherical surfaces, coloured red ; they are at first gorged
with fluid (see section given by Mohl, p. 70), but
ultimately become woody.

As the discs soon adhere firmly to such smooth
surfaces as planed or painted wood, or to the polished
leaf of the ivy, this alone renders it probable that
some cement is secreted, as has been asserted to be '
the case (quoted by Mohl, p. 71) by Malpighi. I
removed a number of discs formed during the previous
year from a stuccoed wall, and left them during many
hours, in warm water, diluted acetic acid and alcohol;
but the attached grains of silex were not loosened.
Immersion in sulphuric ether for 24 hrs. loosened them
much, but warmed essential oils (I tried oil of thyme
and peppermint) completely released every particle of
stone in the course of a few hours. This seems to prove
that some resinous cement is secreted. The quantity,
however, must be small; for when a plant ascended
a thinly whitewashed wall, the discs adhered firmly to
the whitewash ; but as the cement never penetrated
the thin layer, they were easily withdrawn, together
with little scales of the whitewash. It must not be
supposed that the attachment is effected exclusively
by the cement ; for the cellular outgrowth completely
envelopes every minute and irregular projection, and
insinuates itself into every crevice.

A tendril which has not become attached to any
body, does not contract spirally ; and in course of a

148 TENDRIL-BEARERS. Cuar. IV,

week or two shrinks into the finest thread, withers and

Ampelopsis hederacea,

A. Tendril fully developed, with a young leaf on the opposite side of the stem.

B. Older tendril, ‘several weeks after its attachment to a wall, with the branche?
thickened and spirally contracted, and with the extremities developed into discs.
The unattached branches of this tendril have withered and dropped off.

drops off. An attached tendril, on the other hand,
contracts spirally, and thus becomes highly elastic. so

Crap. IV. VITACEA, 149

that when the main foot-stalk is pulled the strain is
distributed equally between all the attached discs.
For a few days after the attachment of the discs, the
tendril remains weak and brittle, but it rapidly increases
in thickness and acquires great strength. During the
following winter it ceases to live, but adheres firmly in
a dead state both to its own stem and to the surface of
attachment. In the accompanying diagram (fig. 11.)
we see the difference between a tendril (B) some weeks
after its attachment to a wall, with one (A) from the
same plant fully grown but unattached. That the
change in the nature of the tissues, as well as the
spiral contraction, are consequent on the formation of
the discs, is well shown by any lateral branches which
have not become attached ; for these in a week or two
wither and drop off, in the same manner as does the
whole tendril if unattached. The gain in strength
and durability in a tendril after its attachment is
something wonderful. There are tendrils now adhering
to my house which are still strong, and have been
exposed to the weather in a dead state for fourteen or
fifteen years. One single lateral branchlet of a tendril,
estimated to be at least ten years old, was still elastic
and supported a weight of exactly two pounds. The
whole tendril had five disc-bearing branches of equal
thickness and apparently of equal strength; so that
after having been exposed during ten years to the
weather, it would probably have resisted a strain of
ten pounds !

Sarinpacea£.—Cardiospermum halicacabum.—In this

150 TENDRIL-BEARERS. Cuar. IV.

family, as in the last, the tendrils are modified flower-
peduncles. In the present plant the two lateral
branches of the main flower-peduncle have been con-
verted into a pair of tendrils, corresponding with the
single “ flower-tendril” of the common vine. The
main peduncle is thin, stiff, and from 3 to 44 inches in
length. Near the summit, above two little bracts, it
divides into three branches. The middle one divides

Fig. 12.
Cardiospermum. halicacabum.
Upper part of the flower-peduncle with its two tendrils,

and re-divides, and bears the flowers; ultimately it
grows half as long again as the two other modified
branches. These latter are the tendrils; they are at
first thicker and longer than the middle branch, but
never become more than an inch in length. They
taper to a point and are flattened, with the lower
clasping surface destitute of hairs. At first they project
straight up; but soon diverging, spontaneously curl
downwards so as to become symmetrically and elegantly
hooked, as represented in the diagram. They are now,
whilst the flower-buds are still small, ready for
action.

Cur. IV. SAPINDACEA. 151

The two or three upper internodes, whilst young,
steadily revolve ; those on one plant made two circles,
against the course of the sun, in 3hrs. 12m.; in a
second plant the same course was followed, and the
two circles were completed in 3 hrs. 41 m.; in a third
plant, the internodes followed the sun and made two
circles in 3hrs. 47m. The average rate of these six
revolutions was lhr. 46m. The stem shows no
tendency to twine spirally round a support; but the
allied tendril-bearing genus Pauilinia is said (Mohl, p.
4) to be a twiner. The flower-peduncles, which stand
up above the end of the shoot, are carried round and
round by the revolving movement of the internodes ;
and when the stem is securely tied, the long and
thin flower-peduncles themselves are seen to be in
continued and sometimes rapid movement from side
to side. They sweep a wide space, but only occasion-
ally revolve in a regular elliptical course. By the
combined movements of the internodes and peduncles,
one of the two short hooked tendrils, sooner or later,
catches hold of some twig or branch, and then it curls
round and securely grasps it. These tendrils are, how-
ever, but slightly sensitive ; for by rubbing their under
surface only a slight movement is slowly produced.
T hooked a tendril on to a twig ; and in 1 hr. 45 m. it
was curved considerably inwards; in 2hrs. 30m. it
formed a ring; and in from 5 to 6 hours from being
first hooked, it closely grasped the stick. A second
tendril acted at nearly the same rate; but I observed
one that took 24 hours before it curled twice round a

152 TENDRIL-BEARERS, Cuar. IV.

thin twig. Tendrils which have caught nothing, spon-
taneously curl up to a close helix after the inter-
val of several days. Those which have curled round
some object, soon become a little thicker and tougher.
The long and thin main peduncle, though sponta-
neously moving, is not sensitive and never clasps a
support. Nor does it ever contract spirally,* although a
contraction of this kind apparently would have been of
service to the plant in climbing. Nevertheless it
climbs pretty well without this aid. The seed-capsules
though light, are of enormous size (hence its English
name of balloon-vine), and as two or three are carried
on the same peduncle, the tendrils rising close to
them may be of service in preventing their being
dashed to pieces by the wind. In the hothouse the
tendrils served simply for climbing.

The position of the tendrils alone suffices to show
their homological nature. In two instances one of
two tendrils produced a flower at its tip; this, however,
did not prevent its acting properly and curling round
a twig. In a third case both lateral branches which
ought to have been modified into tendrils, produced
flowers like the central branch, and had quite lost
their tendril-structure.

Ihave seen, but was not enabled carefully to observe,
only one other climbing Sapindaceous plant, namely,

* Fritz Miller remarks (ibid. p. that the common peduncle con-
348) that a related genus, Serjania, _ tracts spirally, when, as frequently
differs from Cardiospermum in happens, the tendril bas clasped
bearing only asingle tendril; and _ the plant’s own stem.

Cuar. LY, PASSIFLORACEZ. 1538

Paullinia. It was not in flower, yet bore long forked
tendrils. So that, Paullinia, with respect to its tendrils,
appears to bear the same relation to Cardiospermum
that Cissus does to Vetis.

PassIFLORACEH.—After reading the discussion and
facts given by Mohl (p. 47) on the nature of the
tendrils in this family, no one can doubt that they are
modified flower-peduncles. The tendrils and the
flower-peduncles rise close side by side; and my son,
William EX. Darwin, made sketches for me of their
earliest state of development in the hybrid P. floribunda,
The two organs appear at first as asingle papilla which
gradually divides; so that the tendril appears to be a
modified branch of the flower-peduncle. Myson found
one very young tendril surmounted by traces of floral
organs, exactly like those on the summit of the true
flower-peduncle at the same early age.

Passiflora gracilis—This well-named, elegant, annual
species differs from the other members of the group
observed by me, in the young internodes having the
power of revolving. It exceeds all the other climbing
plants which I have.examined, in the rapidity of its
movements, and all tendril-bearers in the sensitiveness
of the tendrils. The internode which carries the upper
active tendril and which likewise carries one or two
younger immature internodes, made three revolutions,
following the sun, at an average rate of 1 hr.4m.; it
then made, the day becoming very hot, three other
revolutions at an average rate of between 57 and
58 m.; so that the average of all six revolutions was

154 TENDRIL-BEARERS. Cua. LY.

lhr. 1m. The apex of the tendril describes elongated
ellipses, sometimes narrow and sometimes broad, with
their longer axes inclined in slightly different direc-
tions. The plant can ascend a thin upright stick by
the aid of its tendrils; but the stem is too stiff for it
to twine spirally round it, even when not interfered
with by the tendrils, these having been successively
pinched off at an early age.

When the stem is secured, the tendrils are seen to
revolve in nearly the same manner and at the same
rate as the internodes.* The tendrils are very thin,
delicate, and straight, with the exception of the tips,
which are a little curved ; they are from 7 to 9 inches
in length. A half-grown tendril is not sensitive; but
when nearly full-grown they are extremely sensitive.
A single delicate touch on the concave surface of the
tip soon caused one to curve; and in 2 minutes it
formed an open helix. A loop of soft thread weighing
ggnd of a grain (2°02 mg.) placed most gently on the
tip, thrice caused distinct curvature. A bent bit of
thin platina wire weighing only »th of a grain (1:23
mg.) twice produced the same effect; but this latter
weight, when left suspended, did not suffice to cause a
permanent curvature. These trials were made under
a bell-glass, so that the loops of thread and wire were

* Prof. Asa Gray informs me temperature varying from 88°-92°
that the tendrils of P. acerifolia Fuhr.) in the following times,
revolve even at a quicker rate 40 m.,45 m., 384 m., and 46 m.
than those of P. gracilis; four One half-revolution was per
revolutions were completed (the formed in 15 m.

Cuapr. IV. PASSIFLORACEZ. 155

not agitated by the wind. The movement after a touch
is very rapid: I took hold of the lower part of several
tendrils, and then touched their concave tips with a
thin twig and watched them carefully through a lens;
the tips evidently began to bend after the following
intervals—31, 25, 32, 31, 28, 39, 31, and 30 seconds ; so
that the movement was generally perceptible in half a
minute after a touch; but on one occasion it was
distinctly visible in 25 seconds. One of the tendrils
which thus became bent in 31 seconds, had been
touched two hours previously and had coiled into a
helix; so that in this interval it had straightened
itself and had perfectly recovered its irritability.

To ascertain how often the same tendril would
become curved when touched, I kept a plant in my
study, which from being cooler than the hot-house was
not very favourable for the experiment. The extremity
was gently rubbed four or five times with a thin stick,
and this was done as often as it was observed to have
become nearly straight again after having been in
action; and in the course of 54 hrs. it answered to the
stimulus 21 times, becoming each time hooked or
spiral. On the last occasion, however, the movement
was very slight, and soon afterwards permanent spiral
contraction commenced. No trials were made during
the night, so that the tendril would perhaps have
answered a greater number of times to the stimulus ;
though, on the other hand, from having no rest it
might have become exhausted from so many quickly
repeated efforts.

156 TENDRIL-BEARERS. Cuap. LV.

I repeated the experiment made on the Echinocystis,
and placed several plants of this Passiflora so close
together, that their tendrils were repeatedly dragged
over each other; but no curvature ensued. I likewise
repeatedly flirted small drops of water from a brush on
many tendrils, and syringed others so violently that
the whole tendril was dashed about, but they never
became curved. The impact from the drops of water
was felt far more distinctly on my hand than that from
the loops of thread (weighing gjnd of a grain) when
allowed to fall on it from a height, and these loops,
which caused the tendrils to become curved, had been
placed most gently on them. Hence it is clear, that the
tendrils either have become habituated to the touch of
other tendrils and drops of rain, or that they were from
the first rendered sensitive only to prolonged though
excessively slight pressure of solid objects, with the
exclusion of that from other tendrils. To show the
difference in the kind of sensitiveness in different plants
and likewise to show the force of the syringe used, I
may add that the lightest jet from it instantly caused
the leaves of a Mimosa to close; whereas the loop of
thread weighing nd of a grain, when rolled into a
ball and placed gently on the glands at the bases of
the leaflets of the Mimosa, caused no action.

Passiflora punctata.—The internodes do not move,
but the tendrils revolve regularly, A half-grown and
very sensitive tendril made three revolutions, opposed
to the course of the sun, in 3hrs. 5m., 2hrs. 40m,
and 2 hrs. 50 m.; perhaps it might have travelled more

Cuar. IV. PASSIFLORACEZ. 157

quickly when nearly full-grown. A plant was placed
in front of a window, and, as with twining stems, the
light accelerated the movement of the tendril in one
direction and retarded it in the other; the semicircle
towards the light being performed in one instance in
15 m. less time and in a second instance in 20 m. less time
than that required by the semicircle towards the dark
end of the room. Considering the extreme tenuity of
these tendrils, the action of the light on them is
remarkable. The tendrils are long, and, as just stated,
very thin, with the tip slightly curved or hooked.
The concave side is extremely sensitive to a touch—
even a single touch causing it to curl inwards; it
subsequently straightened itself, and was again ready
to act. A loop of soft thread weighing ;{;th of a grain
(4625 mg.) caused the extreme tip to bend; another
time I tried to hang the same little loop on an inclined
tendril, but three times it slid off; yet this extra-
ordinarily slight degree of friction sufficed to make the
tip curl. The tendril, though so sensitive, does not
move very quickly after a touch, no conspicuous move-
ment being observable until 5 or 10m. had elapsed.
The convex side of the tip is not sensitive to a touch
or to a suspended loop of thread. On one occasion I
observed a tendril revolving with the convex side of
the tip forwards, and in consequence it was not able
to clasp a stick, against which it scraped; whereas
tendrils revolving with the concave side forward,
promptly seize any object in their path.

Passiflora quadrangularis—This is a very distinct

158 TENDRIL-BEARERS. Cuar, IV.

species. The tendrils are thick, long, and stiff; they
are sensitive to a touch only on the concave surface
towards the extremity. When a stick was placed so
that the middle of the tendril came into contact with it,
no curvature ensued. In the hothouse a tendril made
two revolutions, each in 2 hrs. 22m.; in a cool room
one was completed in 3 hrs., and a second in 4 hrs.
The internodes do not revolve; nor do those of the
hybrid P. floribunda.

Tacsonia manicata.—Here again the internodes do
not revolve. The tendrils are moderately thin and
long; one made a narrow ellipse in 5 hrs. 20 m., and
the next day a broad ellipse in 5 hrs. 7m. The
extremity being lightly rubbed on the concave surface,
became just perceptibly curved in 7 m., distinctly in
10 m., and hooked in 20 m.

We have seen that the tendrils in the last three
families, namely, the Vitacee, Sapindacee and Passi-
floraceze, are modified flower-peduncles. This is like-
wise the case, according to De Candolle (as quoted
by Mohl), with the tendrils of Brunnichia, one of the
Polygonacew. In two or three species of Modecca, one
of the Papayacew, the tendrils, as I hear from
Prof. Oliver, occasionally bear flowers and fruit; so
that they are axial in their nature.

The Spiral Contraction of Tendrils.

This movement, which shortens the tendrils and
renders them elastic, commences in half a day, or in a
day or two after their extremities have caught some

Cuap. IV. SPIRAL CONTRACTION. 159

object. There is no such movement in any leaf-
climber, with the exception of an occasional trace of
it in the petioles of Tropxolum tricolorum. On the
other hand, the tendrils of all tendril-bearing plants,
contract spirally after they have caught an object with
the following exceptions. Firstly, Corydalis claviculata,
but then this plant might be called a leaf-climber.
Secondly and thirdly, Bignonia unguis with its close
allies, and Cardiospermum; but their tendrils are so
short that their contraction could hardly occur, and
would be quite superfluous. Fourthly, Smilax aspera
offers a more marked exception, as its tendrils are
moderately long. The tendrils of Dicentra, whilst the
plant is young, are short and after attachment only
become slightly flexuous; in older plants they are
longer and then they contract spirally. I have seen
no other exceptions to the rule that tendrils, after
clasping with their extremities a support, undergo
spiral contraction. When, however, the tendril of a
plant of which the stem is immovably fixed, catches
some fixed object, it does not contract, simply because
it cannot; this, however, rarely occurs. In the
common Pea the lateral branches alone contract, and
not the central stem; and with most plants, such as
the Vine, Passiflora, Bryony, the basal portion never
forms a spire.

Thave said that in Corydalis claviculata the end of
the leaf or tendril (for this part may be indifferently
so called) does not contract into a spire. The
branchlets, however, after they have wound round

160 TENDRIL-BEARERS. Cuar. IV.

thin twigs, become deeply sinuous or zigzag. More-
over the whole end of the petiole or tendril, if it seizes
nothing, bends after a time abruptly downwards and
inwards, showing that its outer surface has gone on
growing after the inner surface has ceased to grow.
That growth is the chief cause of the spiral contrac
tion of tendrils may be safely admitted, as shown by
the recent researches of H. de Vries. I will, however,
add one little fact in support of this conclusion.

If the short, nearly straight portion of an attached
tendril of Passiflora gracilis, (and, as I believe, of other
tendrils,) between the opposed spires, be examined, it
will be found to be transversely wrinkled in a con-
spicuous manner on the outside; and this would
naturally follow if the outer side had grown more than
the inner side, this part being at the same time
forcibly prevented from becoming curved. So again
the whole outer surface of a spirally wound tendril
becomes wrinkled if it be pulled straight. Nevertheless,
as the contraction travels from the extremity of a
tendril, after it has been stimulated by contact with a
support, down to the base, I cannot avoid doubting,
from reasons presently to be given, whether the whole
effect ought to be attributed to growth. An unattached
tendril rolls itself up into a flat helix, as in the case of
Cardiospermum, if the contraction commences at the
extremity and is quite regular; but if the continued
growth of the outer surface is a little lateral, or if the
process begins near the base, the terminal portion can-
not be rolled up within the basal portion, and the

Cuar, IV. SPIRAL CONTRACTION. 161

tendril then forms a more or less open spire. A
similar result follows if the extremity has caught
some object, and is thus held fast.

The tendrils of many kinds of plants, if they catch
nothing, contract after an interval of several days or
weeks into a spire; but in these cases the movement
takes place after the tendril has lost its revolving
power and hangs down; it has also then partly or
wholly lost its sensibility ; so that this movement can
be of no use. The spiral contraction of unattached
tendrils is a much slower process than that of attached
ones. Young tendrils which have caught a support
and are spirally contracted, may constantly be seen on
the same stem with the much older unattached and
uncontracted tendrils. In the Echinocystis I have seen a
tendril with the two lateral branches encircling twigs
and contracted into beautiful spires, whilst the main
branch which had caught nothing remained for many
days straight. In this plant I once observed a main
branch after it had caught a stick become spirally
flexuous in 7 hrs. and. spirally contracted in 18 hrs.
Generally the tendrils of the Echinocystis begin to
contract in from 12 hrs. to 24 hrs. after catching
some object ; whilst unattached tendrils do not begin
to contract until two or three or even more days after
all revolving movement has ceased. A full-grown
tendril of Passiflora quadrangularis which had caught
a stick began in 8 hrs. to contract, and in 24 hrs.
formed several spires; a younger tendril, only two-
thirds grown, showed the first trace of contraction in

8

162 TENDRIL-BEARERS. Cuar. IV.

two days after clasping a stick, and in two more
days formed several spires. It appears, therefore, that
the contraction does not begin until the tendril is
grown to nearly its full length. Another young
tendril of about the same age and length as the last
did not catch any object; it acquired its full length
in four days; in six additional days it first became
flexuous, and in two more days formed one com-
plete spire. This first spire was formed towards: the
basal end, and the contraction steadily but slowly
progressed towards the apex; but the whole was not
closely wound up into a spire until 21 days had
elapsed from the first observation, that is, until 17
days after the tendril had grown to its full length.
The spiral contraction of tendrils is quite indepen-
dent of their power of spontaneously revolving, for it
occurs in tendrils, such as those of Lathyrus grandi-
florus and Ampelopsis hederacea, which do not revolve.
It is not necessarily related to the curling of the tips
round a support, as we see with the Ampelopsis and
Bignonia capreolata, in which the development of
adherent discs suffices to cause spiral contraction.
Yet in some cases this contraction seems connected
with the curling or clasping movement, due to contact
with a support; for not only does it soon follow this
act, but the contraction generally begins close to the
curled extremity, and travels downwards to the base.
If, however, a tendril be very slack, the whole length
almost simultaneously becomes at first flexuous and
then spiral. Again, the tendrils of some few plants

Crap. IV. SPIRAL CONTRACTION, 163

never contract spirally unless they have first seized
hold of some object; if they catch nothing they hang
down, remaining straight, until they wither and drop
off: this is the case with the tendrils of Bignonia,
which consist of modified leaves, and with those of
three genera of the Vitacez, which are modified flower-
peduncles. But inthe great majority of cases, tendrils
which have never come in contact with any object,
after a time contract spirally. All these facts taken
together, show that the act of clasping a support and
the spiral contraction of the whole length of the
tendril, are phenomena not necessarily connected.

The spiral contraction which ensues after a tendril
has caught a support is of high service to the plant;
hence its almost universal occurrence with species
belonging to widely different orders. When a shoot
is inclined and its tendril has caught an object above,
the spiral contraction drags up the shoot. When the
shoot is upright, the growth of the stem, after the
tendrils have seized some object above, would leave it
slack, were it not for the spiral contraction which
draws up the stem as it increases in length. Thus
there is no waste of growth, and the stretched stem
ascends by the shortest course. When a terminal
branchlet of the tendril of Cobsa catches a stick, we
have seen how well the spiral contraction successively
brings the other branchlets, one after the other, into
contact with the stick, until the whole tendril grasps
it in an inextricable knot. When a tendril has caught
a yielding object, this is sometimes enveloped and

164 TENDRIL-BEARERS, Cuar. IV,

still further secured by the spiral folds, as I have seen
with Passiflora quadrangularis ; but this action is of
little importance.

A far more important service rendered by the spiral
contraction of the tendrils is that they are thus made
highly elastic. As before remarked under Ampelopsis,
the strain is thus distributed equally between the
several attached branches; and this renders the whole
far stronger than it otherwise would be, as the branches
cannot break separately. It is this elasticity which pro-
tects both branched and simple tendrils from being torn
away from.their supports during stormy weather. I
have more than once gone on purpose during a gale to
watch a Bryony growing in an exposed hedge, with
its tendrils attached to the surrounding bushes; and
as the thick and thin branches were tossed to and fro
by the wind, the tendrils, had they not been excessively
elastic, would instantly have been torn off and the
plant thrown prostrate. But as it was, the Bryony
safely rode out the gale, like a ship with two anchors
down, and with along range of cable ahead to serve
as a spring as she surges to the storm.

When an unattached 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, although the same side is
concave from end to end, invariably becomes twisted
in one part in one direction, and in another part in the
opposite direction ; the oppositely turned spires being
separated by a short straight portion. This curious

Unae. IV. SPIRAL CONTRACTION. 165

and symmetrical structure has been noticed by several
botanists, but has not been sufficiently explained.* It
occurs without exception with all tendrils which after
catching an object contract spirally, but is of course
most conspicuous in the longer tendrils. It never
occurs with uncaught tendrils; and when this appears
to have occurred, it will be found that the tendril had
originally seized some object and had afterwards been
tom free. Commonly, all the spires at one end of an
attached tendril run in one direction, and all those at

Fig. 13.
A caught tendril of Bryonta divica, spirally contracted in reversed directions.

the other end in the opposite direction, with a single
short straight portion in the middle; but I have seen
a tendril with the spires alternately turning five times

* See M. Isid. Léon in Bull.
Soc. Bot. de France, tom. v. 1858,
p. 680. Dr. H. de Vries points

wind into a spire, which, since
the tendril is made fast at both
extremities, must of necessity be

out (p. 306) that I have overlooked,
in the first edition of this essay,
the following sentence by Mohl:
“After a tendril has caught a
eupport, it begins in some days to

in some places to the right, in
others to the left.” But I am not
surprised that this brief sentence,
without any further explanation
did not attract my aitention,

{66 TENDRIL-BEARERS. Cuar. 1V

in opposite directions, with straight pieces between
them; and M. Léon has seen seven or eight such
alternations. Whether the spires turn once or more
than once in opposite directions, there are as many
turns in the one direction as in the other. For
instance, I gathered ten attached tendrils of the
Bryony, the longest with 33, and the shortest with
only 8 spiral turns; and the number of turns in the
one direction was in every case the same (within one)
as in the opposite direction.

The explanation of this curious little fact is not
difficult. I will not attempt any geometrical reasoning,
but will give only a practical illustration. In doing
this, I shall first have to allude to a point which was
almost passed over when treating of Twining-plants.
Tf we hold in our left hand a bundle of parallel strings,
we can with our right hand turn these round and
round, thus imitating the revolving movement of a
twining plant, and the strings do not become twisted.
But if we hold at the same time a stick in our
left hand, in such a position that the strings become
spirally turned round it, they will inevitably become
twisted. Hence a straight coloured line, painted along
the internodes of a twining plant before it has wound
round a support, becomes twisted or spiral after it has
wound round. I painted a red line on the straight
internodes of a Humulus, Mikania, Ceropegia, Con-
volvulus, and Phaseolus, and saw it become twisted as
the plant wound round a stick. It is possible that
the stems of some plants by spontaneously turning on

Cuap. IV. SPIRAL CONTRACTION. 167

their own axes, at the proper rate and in the proper
direction, might avoid becoming twisted; but I have
seen no such case.

In the above illustration, the parallel strings were
wound round a stick; but this is by no means neces-
sary, for if wound into a hollow coil (as can be done
with a narrow slip of elastic paper) there is the same
inevitable twisting of the axis. When, therefore, a free
tendril coils itself into a spire, it must either become
twisted along its whole length (and this never occurs),
or the free extremity must turn round as many times
as there are spires formed. It was hardly necessary
to observe this fact; but I did so by affixing little
paper vanes to the extreme points of the tendrils of
Echinocystis and Passifiora quadrangularis; and as
the tendril contracted itself into successive spires, the
yane slowly revolved.

We can now understand the meaning of the spires
being invariably turned in opposite directions, in
tendrils which from having caught some object are
fixed at both ends. Let us suppose a caught tendril
to make thirty spiral turns all in the same direction;
the inevitable result would be that it would become
twisted thirty times on its own axis. This twisting
would not only require considerable force, but, as I
know by trial, would burst the tendril before the thirty
turns were completed. Such cases never really occur ;
for, as already stated, when a tendril has caught a
support and is spirally contracted, there are always
as many turns in one direction as in the other; so that

168 TENDRIL-BEARERS, Cuar. IV.

the twisting of the axis in the one direction is exactly
compensated by the twisting in the opposite direction.
We can further see how the tendency is given to make
the later formed coils opposite to those, whether turned
to the right or to the left, which are first made. Take
a piece of string, and let it hang down with the lower
end fixed to the floor; then wind the upper end
(holding the string quite loosely) spirally round a per-
pendicular pencil, and this will twist the lower part of
the string ; and after it has been sufficiently twisted, it
will be seen to curve itself into an open spire, with the
curves running in an opposite direction to those round
the pencil, and consequently with a straight piece of
string between the opposed spires. In short, we have
given to the string the regular spiral arrangement of a
tendril caught at both ends. The spiral contraction
generally begins at the extremity which has clasped a
support; and these first-formed spires give a twist to the
axis of the tendril, which necessarily inclines the basal
part into an opposite spiral curvature. I cannot resist
giving one other illustration, though superfluous:
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

Cuap. IV. SUMMARY. 169

direction; but in both cases the self-twisting is
avoided.

Summary on the Nature and Action of Tendrils.

With the majority of tendril-bearing plants the young
internodes revolve in more or less broad ellipses, like
those made by twining plants; but the figures de-
scribed, when carefully traced, generally form irregular
ellipsoidal spires. The rate of revolution varies from
one to five hours in different species, and consequently
is in some cases more rapid than with any twining
plant, and is never so slow as with those many twiners
which take more than five hours for each revolution.
The direction is variable‘even in the same individual
plant. In Passiflora,. the internodes of only one
species have the power of revolving. The Vine is
the weakest revolver observed by me, apparently
exhibiting only a trace of a former power. In the
Kecremocarpus the movement is interrupted by many
long pauses. Very few tendril-bearing plants can
spirally twine up an upright stick. Although the
power of twining has generally been lost, either from
the stiffness or shortness of the internodes, from the size
of the leaves, or from some other unknown cause, the
revolving movement of the stem serves to. bring the
tendrils into contact with surrounding objects.

The tendrils themselves also spontaneously. revolve.
The movement begins whilst the tendril is young, and
is at first slow. The mature tendrils of Bignonia littoralis
move much slower than the internodes. Generally,

170 TENDBIL-BEARERS. Cuar. IV.

the internodes and tendrils revolve together at the
same rate; in Cissus, Cobaa, and most Passifiors, the
tendrils alone revolve ; in other cases, as with Lathyrus
aphaca, only the internodes move, carrying with them
the motionless tendrils; and, lastly (and this is the
fourth possible case), neither internodes nor tendrils
spontaneously revolve, as with Lathyrus grandiflorus
and Ampelopsis. In most Bignonias, Eccremocarpus,
Mutisia, and the Fumariacee, the internodes, petioles
and tendrils all move harmoniously together. In
every case the conditions of life must be favourable in
order that the different parts should act in a perfect
manner.

Tendrils revolve by the curvature of their whole
length, excepting the sensitive extremity and the
base, which parts do not move, or move but little.
The movement is of the same nature as that of the
revolving internodes, and, from the observations of
Sachs and H. de Vries, no doubt is due to the same
cause, namely, the rapid growth of a longitudinal band,
which travels round the tendril and successively bows
each part to the opposite side. Hence, if a line be
painted along that surface which happens at the time
to be convex, the line becomes first lateral, then
concave, then lateral, and ultimately again convex.
This experiment can be tried only on the thicker
tendrils, which are not affected by a thin crust of
dried paint. The extremities are often slightly curved
or hooked, and the curvature of this part is never
reversed; in this respect they differ from the ex-

Cuar. IV. SUMMARY. 171

tremities of twining shoots, which not only reverse
their curvature, or at least become periodically straight,
but curve themselves in a greater degree than the ‘
lower part. In most other respects a tendril acts as if
it were one of several revolving internodes, which all
move together by successively bending to each point
of the compass. There is, however, in many cases this
unimportant difference, that the curving tendril is
separated from the curving internode by a rigid
petiole. With most tendril-bearers the summit of the
stem or shoot projects above the point from which
the tendril arises; and it is generally bent to one side,
so as to be out of the way of the revolutions swept by
the tendril. In those plants in which the terminal
shoot is not sufficiently out of the way, as we have
seen with the Echinocystis, as soon as the tendril
comes in its revolving course to this point, it stiffens
and straightens itself, and thus rising vertically up
passes over the obstacle in an admirable manner.

All tendrils are sensitive, but in various degrees, to
contact with an ubject, and curve towards the touched
side. With several plants a single touch, so slight as
only just to move the highly flexible tezidril, is enough
to induce curvature. Passiflora gracilis possesses the
most sensitive tendrils which I have observed: a bit
of platina wire 35th of a grain (1:23 mg.) in weight,
gently placed on the concave point, caused a tendril
to become hooked, as did a loop of soft, thin cotton
thread weighing jynd of a grain (202 mg.) With the
tendrils of several other plants, loops weighing jth of

172 TEN DRIL-BEARERS. Cuar. IV,

a grain (4:05 mg.) sufficed. The point of a tendril of
Passiflora gracilis began to move distinctly in 25
seconds after a touch, and in many cases after 30
seconds. Asa Gray also saw movement in the tendrils
of the Cucurbitaceous genus, Sicyos, in 30 seconds.
The tendrils of some other plants, when lightly
rubbed, moved in a few minutes; with Dicentra in
half-an-hour ; with Smilax in an hour and a quarter
or half; and with Ampelopsis still more slowly.
The curling movement consequent on a single touch
continues to increase for a considerable time, then
ceases ; after a few hours the tendril uncurls itself, and
is again ready to act. When the tendrils of several
kinds of plants were caused to bend by extremely
light weights suspended on them, they seemed to grow
accustomed to so slight a stimulus, and straightened
themselves, as if the loops had been removed. It
makes no difference what sort of object a tendril
touches, with the remarkable exception of other ten-
drils and drops of water, as was observed with the
extremely sensitive-tendrils of Passiflora gracilis and
of the Echinocystis. I have, however, seen tendrils
of the Bryony which had temporarily caught other
tendrils, and often in the case of the vine.

Tendrils of which the extremities are permanently
and slightly curved, are sensitive only on the concave
surface; other tendrils, such as those of the Cobza
(though furnished with horny hooks directed to one side)
and those of Cissus discolor, are sensitive on all sides.
Hence the tendrils of this latter plant, when stimulated

Cuar. IV. SUMMARY. 173

by # touch of equal force on opposite sides, did not
bend. The inferior and lateral surfaces of the tendrils
of Mutisia are sensitive, but not the upper surface.
With branched tendrils, the several branches act
alike; but in the Hanburya the lateral spur-like
branch does not acquire (for excellent reasons which
have been explained) its sensitiveness nearly so
soon as the main branch. With most tendrils the
lower or basal part is either not at all sensitive, or
sensitive only to prolonged contact. We thus see
that the sensitiveness of tendrils is a special and
localized capacity. It is quite independent of the
power of spontaneously revolving; for the curling of
the terminal portion from a touch does not in the least
interrupt the former movement. In Bignonia unguis
and its close allies, the petioles of the leaves, as well
as the tendrils, are sensitive to a touch.

Twining plants when they come into contact with a
stick, curl round it invariably in the direction of their
revolving movement; but tendrils curl indifferently
to either side, in accordance with the position of the
stick and the side which is first touched. The clasping
movement of the extremity is apparently not steady,
but undulatory or vermicular in its nature, as may be
inferred from the curious manner in which the tendrils
of the Echinocystis slowly crawled round a smooth
stick.

As with a few exceptions tendrils spontaneously
revolve, it may be asked,—why have they been endowed
with sensitiveness ?—why, when they come into contact

174 TENDRIL-BEARERS. Cuar. IV.

with a stick, do they not, like twining plants, spirally
wind round it? One reason may be that they are in
most cases so flexible and thin, that when brought
into contact with any object, they would almost
certainly yield and be dragged onwards by the revolv-
ing movement. Moreover, the sensitive extremities
have no revolving power as far as I have observed,
and could not by this means curl round a support.
With twining plants, on the other hand, the extremity
spontaneously bends more than any other part; and
this is of high importance for the ascent of the plant,
as may beseen on a windy day. It is, however, possible
that the slow movement of the basal and stiffer parts
of certain tendrils, which wind round sticks placed in
their path, may be analogous to that of twining plants.
But I hardly attended sufficiently to this point, and it
would have been difficult to distinguish between a
movement due to extremely dull irritability, from the
arrestment of the lower part, whilst the upper part
continued to move onwards.

Tendrils which are only three-fourths grown, and
~ perhaps even at an earlier age, but not whilst extremely
young, have the power of revolving and of grasping
any object which they touch. These two capacities
are generally acquired at about the same period, and
both fail when the tendril is full grown. But in
Cobea and Passiflora punctata the tendrils begin to
revolve in a useless manner, before they have become
sensitive. In the Echinocystis they retain their
sensitiveness for some time after they have ceased tc

Cuar. IV. SUMMARY. 175

revolve and after they have sunk downwards; in this
position, even if they were able to seize an object, such
power would be of no service in supporting the stem.
It is a rare circumstance thus to detect any super-
fluity or imperfection in the action of tendrils—organs
which are so excellently adapted for the functions
which they have to perform; but we see that they are
not always perfect, and it would be rash to assume
that any existing tendril has reached the utmost limit
of perfection.

Some tendrils have their revolving motion accelerated
or retarded, in moving to or from the light; others,
as with the Pea, seem indifferent to its action; others
move steadily from the light to the dark, and this aids
them in an important manner in finding a support.
For instance, the tendrils of Bignonia capreolata bend
from the light to the dark as truly as a wind-vane from
the wind. Inthe Eccremocarpus the extremities alone
twist and turn about so as to bring their finer branches
and hooks into close contact with any dark surface, or
into crevices and holes.

A short time after a tendril has caught a support,
it contracts with some rare exceptions into a spire;
but the manner of contraction and the several important
advantages thus gained have been discussed so lately,
that nothing need here be repeated on the subject.
Tendrils soon after catching a support grow much
stronger and thicker, and sometimes more durable to a
wonderful degree; and this shows how much their
internal tissues must be changed. Occasionally it is

176 TENDRIL-BEARERS. Cuap. 1V.

the part which is wound round a support which
chiefly becomes thicker and stronger; I have seen,
for instance, this part of a tendril of Bignonia xqui-
noctialis twice as thick and rigid as the free basal part.
Tendrils which have caught nothing soon shrink and
wither; but in some species of Bignonia they disarti-
culate and fal] off like leaves in autumn.

Any one who had not closely observed tendrils of
many kinds would probably infer that their action was
uniform. This is the case with the simpler kinds,
which simply curl round an object of moderate thick-
ness, whatever its nature may be.* But the genus
Bignonia shows us what diversity of action there may
be between the tendrils of closely allied species. In
all the nine species observed by me, the young in-
ternodes revolve vigorously; the tendrils also re-
volve, but in some of the species in a very feeble
manner ; and lastly the petioles of nearly all revolve,
though with unequal power. The petioles of three of the
species, and the tendrils of all are sensitive to contact.
In the first-described species, the tendrils: res mble
in shape a bird’s foot, and they are of no service to the
stem in spirally ascending a thin upright stick, but
they can seize firm hold of a twig or branch. When

* Sachs, however (‘‘Text-Book adapted to clasp supports of
of Botany,’ Eng. Translation,J875, different thicknesses. He further
p. 280), bas shown that which shows that after a tendril has
I overlooked, namely, that the clasped a support it subsequently
tendrils of different species are _ tightens its hold.

(aap. IV. SUMMARY, 177

the stem twines round a somewhat thick stick, a slight
degree of sensitiveness possessed by the petioles is
brought into play, and the whole leaf together with
the tendril winds round it. In B. ungwis the petioles
are more sensitive, and have greater power of move-
ment than those of the last species; they are able,
together with the tendrils, to wind inextricably round
a thin upright stick; but the stem does not twine
so well. B. Tweedyana has similar powers, but in
addition, emits aérial roots which adhere to the wood.
In B. venusta the tendrils are converted into elongated
three-pronged grapnels, which move spontaneously in
a conspicuous manner; the petioles, however, have lost
their sensitiveness. The stem of this species can twine
round an upright stick, and is aided in its ascent by
the tendrils seizing the stick alternately some way
above and then contracting spirally. In B. hittoralis
the tendrils, petioles, and internodes, all revolve spon-
taneously The stem, however, cannot twine, but ascends
an upright stick by seizing it above with both tendrils
together, which then contract into a spire. The tips
of these tendrils become developed into adhesive discs.
B. speciosa possesses similar powers of movement as
the last species, but it cannot twine round a stick,
though it can ascend by clasping the stick horizon-
tally with one or both of its unbranched tendrils.
These tendrils continually insert their pointed ends
into minute crevices or holes, but as they are always
withdrawn by the subsequent spiral contraction, the
habit seems to us in our ignorance useless. Lastly,

[78 . TENDRIL-BEARERS. Cuar. IV.

the stem of B. capreolata twines imperfectly ; the much-
branched tendrils revolve in a capricious manner, and
bend from the light to the dark; their hooked ex-
tremities, even whilst immature, crawl into crevices,
and, when mature, seize any thin projecting point;
in either case they develop adhesive discs, and these
have the power of enveloping the finest fibres.

In the allied Eccremocarpus the internodes, petioles,
and much-branched tendrils all spontaneously revolve
together. The tendrils do not as a whole turn from
the light ; but their bluntly-hooked extremities arrange
themselves neatly on any surface with which they
come into contact, apparently so as to avoid the light.
They act best when each branch seizes a few thin
stems, like the culms of a grass, which they after-
wards draw together into a solid bundle by the spiral
contraction of all the branches. In Cobwa the
finely-branched tendrils alone revolve; the branches
terminate in sharp, hard, double, little hooks, with
both points directed to the same side; and these turn
by well-adapted movements to any object with which
they come into contact. The tips of the branches
also crawl into dark crevices or holes. The tendrils
and internodes of Ampelopsis have little or no power
of revolving; the tendrils are but little sensitive to
contact; their hooked extremities cannot seize thin
objects; they will not even clasp a stick, unless in
extreme need of a support; but they turn from the
light to the dark, and, spreading out their branches in
contact with any nearly flat surface, develop discs

Cur. IV. SUMMARY. 179

These adhere by the secretion of some cement to a
wall, or even to a polished surface; and this is more
than the discs of the Bignonia capreolata can effect.

The rapid development of these adherent discs is
one of the most remarkable peculiarities possessed by
any tendrils. We have seen that such discs are formed
by two species of Bignonia, by Ampelopsis, and,
according to Naudin,* by the Cucurbitaceous genus
Peponopsis adherens. In Anguria the lower surface of
the tendril, after it has wound round a stick, forms
a coarsely cellular layer, which closely fits the wood,
but is not adherent; whilst in Hanburya a similar
layer is adherent. The growth of these cellular out-
growths depends, (except in the case of the Haplolophium
and of one species of Ampelopsis,) on the stimulus from
contact. It is a singular fact that three families, so
widely distinct as the Bignoniacee, Vitacee, and
Cucurbitacee, should possess species with tendrils
having this remarkable power.

Sachs attributes all the movements of tendrils to
rapid growth on the side opposite to that which
becomes concave. These movements consist of re-
volving nutation, the bending to and from the light,
and in opposition to gravity, those caused by a touch,
and spiral contraction. Itis rash to differ from so great
an authority, but I cannot believe that one at least of

* Annales des Sc. Nat. Bot. 4th series, tum. xii. p. 89.

180 TENDRIL-BEARERS. Cuar. IV.

these movements—curvature from a touch—is thus
caused.* In the first place it may be remarked that the
movement of nutation differs from that due toa touch,
in so far that in some cases the two powers are acquired
by the same tendril at different periods of growth;
and the sensitive part of the tendril does not seem
capable of nutation. One of my chief reasons for doubt-
ing whether the curvature from a touch is the result
of growth, is the extraordinary rapidity of the move-
ment. I have seen the extremity of a tendril of
Passiflora gracilis, after being touched, distinctly bent
in 25 seconds, and often in 30 seconds; and so it is
with the thicker tendril of Sicyos. It appears hardly
credible that their outer surfaces could have actually
grown in length, which implies a permanent modifica-
tion of structure, in so short a time. The growth,
moreover, on this view must be considerable, for if the
touch has been at all rough the extremity is coiled
in two or three minutes into a spire of several turns.
When the extreme tip of the tendril of Echinocystis
caught hold of a smooth stick, it coiled itself in a
few hours (as described at p. 182) twice or thrice round

* It occurred to me that the cilis, but I succeeded only in ob-
movement of nutation and that serving that both movements were
from a touch might be differently unaffected by exposure for 14 hrs.
affected by anesthetics, in the toarather large dose of sulphu-
same manner as Paul Bert has ric ether. In this respect they
shown to be the case with the present a wonderful contrast with
sleep-movements of Mimosa and Drosera, owing no doubt to the
those from a touch. I tried the presence of absorbent glands in
common pea and Passiflora gra- the latter plant,

Cuar. IY. SUMMARY, 181

the stick, apparently by an undulatory movement. At
first I attributed this movement to the growth of the
outside; black marks were therefore made, and the
interspaces measured, but I could not thus detect any
increase in length. Hence it seems probable in this
case and in others, that the curvature of the tendril
from a touch depends on the contraction of the cells
along the concave side. Sachs himself admits* that
« if the growth which takes place in the entire tendril
“at the time of contact with a support is small, a
“ considerable acceleration occurs on the convex sur
“face, but in general there is no elongation on the
“ concave surface, or there may even be a contraction ;
“in the case of a tendril of Cucurbita this contraction
“ amounted to nearly one-third of the original length.”
In a subsequent passage Sachs seems to feel some diffi-
culty in accounting for this kind of contraction. It
must not however be supposed from the foregoing
remarks that I entertain any doubt, after reading De
Vries’ observations, about the outer and _ stretched
surfaces of attached tendrils afterwards increasing in
length by growth. Such increase seems to me quite
compatible with the first movement being independent
of growth. Why a delicate touch should cause one
side of a tendril to contract we know as little as why,
on the view held by Sachs, it should lead to extra-
ordinarily rapid growth of the opposite side. The
chief or sole reason for the belief that the curvature of

* *Text-Book of Botany, 1875, p. 779.

182 TENDRIL-BEARERS. Cuap. IV.

a tendril when touched is due to rapid growth, seems to
be that tendrils lose their sensitiveness and power of
movement after they have grown to their full length;
but this fact is intelligible, if we bear in mind that all
the functions of a tendril are adapted to drag up the
terminal growing shoot towards the light. Of what
use would it be, if an old and full-grown tendril,
arising from the lower part of a shoot, were to retain
its power of clasping a support? This would be of
no use; and we have seen with tendrils so many in-
stances of close adaptation and of the economy of
means, that we may feel assured that they would
acquire irritability and the power of clasping a support
at the proper age—namely, youth—and would not
uselessly retain such power beyond the proper age.

HOOK-CLIMBERS, 183

CHAPTER V.

Hook ant Root-Cirmpers.—Conxcicpine Remarks.

Plunts climbing by the aid of hooks, or merely scrambling over other
plants—Root-climbers, adhesive matter secreted by the rootlets—
General conclusions with respect to climbing plants, and the stages
of their development,

Hook-Climbers.—In my introductory remarks, I stated
that, besides the two first great classes of climbing
plants, namely, those which twine round a support,
and those endowed with irritability enabling them to
seize hold of objects by means of their petioles or
tendrils, there are two other classes, hook-climbers and
root-climbers. Many plants, moreover, as Fritz Miller
has remarked,* climb or scramble up thickets in a still
more simple fashion, without any special aid, excepting
that their leading shoots are generally long and flexible.
It may, however, be suspected from what follows, that
these shoots in some cases tend to avoid the light.
The few hook-climbers which I have observed, namely,
Galiwm aparine, Rubus australis, and some climbing

* Journal of Linn. Soc. vol. ix.
p. 348, Professor G. Jaeger has well
remarked (‘In Sachen Darwin’s,
insbesoudere contra Wigand,’
1874, p. 106) that it is highly
characteristic of climbing plants to
produce thin, elongated, ard flexi-
ble stems, He further remarks that

plants growing beneath other and
taller species or trees, are naturally
those which would be develop.d
into climbers; and such plants,
from stretching towards the light,
and {rom not being much agitated
by the wind, tend to produce long,
thin and flexible shoots,

184 HOOK-CLIMBERS. Cuar. V.

Roses, exhibit no spontaneous revolving movement.
If they had possessed this power, and had been capable
of twining, they would have been placed in the class
of Twiners ; for some twiners are furnished with spines
or hooks, which aid them in their ascent. For instance,
the Hop, which is a twiner, has reflexed hooks as large
as those of the Galiwm ; some other twiners have stiff
reflexed hairs; and Dipladenia has a circle of blunt
spines at the bases of its leaves. I have seen only
one tendril-bearing plant, namely, Smilax aspera, which
is furnished with reflexed spines; but this is the case
with several branch-climbers in South Brazil and
Ceylon; and their branches graduate into true tendrils.
Some few plants apparently depend solely on their
hooks for climbing, and yet do so efficiently, as certain
palms in the New and Old Worlds. Even some
climbing Roses will ascend the walls of a tall house,
if covered with a trellis. How this is effected I know
not; for the young shoots of one such Rose, when
placed in a pot in a window, bent irregularly towards
the light during the day and from the light during the
night, like the shoots of any common plant; so that
it is not easy to understand how they could have got
under a trellis close to the wall.*

+ Professor Asa Gray has ex-
plained, as it would appear, this
difficulty in his review (American
Journal of Science, vol. xl. Sept.
1865, p. 282) of the present work,
He has observed that the strong
summer shoots of the Michigan
rose (Hosa setigera) are strongly

disposed to push into dark crevices
and away from the light, so that
they would be almost sure to
place themselves under a trellis,
He adds that the lateral shoots,
made on the following spring,
emerged from the trellis as they
sought the light,

Cur. V. ROOT-CLIMBERS. 185

Root-climbers.—A. good many plants come under this
class, and are excellent climbers. One of the most
remarkable is the Marcgravia umbellata, the stem of
which in the tropical forests of South America, as I
hear from Mr. Spruce, grows in a curiously flattened
manner against the trunks of trees; here and there
it puts forth claspers (roots), which adhere to the
trunk, and, if the latter be slender, completely embrace
it. When this plant has climbed to the light, it pro-
duces free branches with rounded stems, clad with sharp-
pointed leaves, wonderfully different in appearance from
those borne by the stem as long as it remains adherent.
This surprising difference in the leaves, I have also
observed in a plant of Maregravia dubia in my hothouse.
Root-climbers, as far as I have seen, namely, the Ivy
(Hedera helix), Ficus repens, and F. barbatus, have no
power of movement, not even from the light to the dark.
As previously stated, the Hoya carnosa (Asclepiadaceze)
is a spiral twiner, and likewise adheres by rootlets
even to a flat wall. The tendril-bearing Bignonia
Tweedyana emits roots, which curve half round and
adhere to thin sticks. The Tecoma radicans (Big-
noniacex), which is closely allied to many spontane-
ously revolving species, climbs by rootlets; never-
theless, its young shoots apparently move about more
than can be accounted for by the varying action of
the light.

T have not closely observed many root-climbers, but
can give one curious fact. Ficus repens climbs up

a wall just like Ivy;.and when the young rootlets
9

186 ROOT-CLIMBERS. Cua. V.

are made to press lightly on slips of glass, they emit
after about a week’s interval, as I observed several
times, minute drops of clear fluid, not in the least
milky like that exuded from a wound. This fluid
is slightly viscid, but cannot be drawn out into
threads. It has the remarkable property of not soon
drying ; a drop, about the size of half a pin’s head, was
slightly spread out on glass, and I scattered on it some
minute grains of sand. The glass was left exposed
in a drawer during hot and dry weather, and if the
fluid had been water, it would certainly have dried
in a few minutes; but it remained fluid, closely
surrounding each grain of sand, during 128 days: how
much longer it would have remained I cannot say.
Some other rootlets were left in contact with the glass
for about ten days or a fortnight, and the drops of
secreted fluid were now rather larger, and so viscid
that they could be drawn out into threads. Some
other rootlets were left in contact during twenty-three
days, and these were firmly cemented to the glass.
Hence we may conclude that the rootlets first secrete
a slightly viscid fluid, subsequently absorb the watery
parts, (for we have seen that the fluid will not dry
by itself,) and ultimately leave a cement. When the
rootlets were torn from the glass, atoms of yellowish
matter were left. on it, which were partly dissolved
by a drop of bisulphide of carbon ; and this extremely
volatile fluid was rendered very much less volatile by
what it had dissolved.

As the bisulphide of carbon has a strong power

Cuap. V. ROUT-CLIMBERS, 187

of softening indurated caoutchouc, I soaked in it
during a short time several rootlets of a plant which
had grown up a plaistered wall; and I then found
many extremely thin threads of transparent, not viscid,
excessively elastic matter, precisely like caoutchouc,
attached to two sets of rootlets on the same branch.
These threads proceeded from the bark of the rootlet
at one end, and at the other end were firmly attached
to particles of silex or mortar from the wall. There
could be no mistake in this observation, as I played
with the threads for a long time under the microscope,
drawing them out with my dissecting-needles and
letting them spring back again. Yet I looked re-
peatedly at other rootlets similarly treated, and could
never again discover these elastic threads. I there-
fore infer that the branch in question must have been
slightly moved from the wall at some critical period,
whilst the secretion was in the act of drying, through
the absorption of its watery parts. The genus Ficus
abounds with caoutchouc, and we may conclude from
the facts just given that this substance, at first in
solution and ultimately modified into an unelastic
cement,* is used by the Ficus repens to cement its
rootlets to any surface which it ascends. Whether
other plants, which climb by their rootlets, emit
any cement I do not know; but the rootlets of the

* Mr. Spiller has recentlyshown a fine state of division to the air,
(Chemical Society, Feb. 16,1865), gradually becomes converted into
in a paper on the oxidation of _ brittle, resinous matter, very similar
india-rubber or caoutchouc, that to sheli-lac,
this substance, when exposed in

188 ROOT-CLIMBERS. Cuar. V.

Ivy, placed against glass, barely adhered to it, yet
secreted a little yellowish matter. I may add, that the
rootlets of the Marcgravia dubia can adhere firmly to
smooth painted wood.

Vanilla aromatica emits aérial roots a foot in length,
which point straight down to the ground. According
to Mohl (p. 49), these crawl into crevices, and when
they meet with a thin support, wind round it, as do
tendrils. A plant which I kept was young, and did
not form long roots; but on placing thin sticks in
contact with them, they certainly bent a little to that
side, in the course of about a day, and adhered by
their rootlets to the wood; but they did not bend
quite round the sticks, and afterwards they re-pursued
their downward course. It is probable that these slight
movements of the roots are due to the quicker growth
of the side exposed to the light, in comparison with
the other side, and not because the roots are sensitive
to contact in the same manner as true tendrils. Ac-
cording to Mohl, the rootlets of certain species of
Lycopodium act as tendrils.*

* Fritz Miller informs me
that he saw in the forests of
South Brazil uumerous black
strings, from, some lines to nearly
an inch in diameter, winding
spirally round the trunks of gi-
gantic trees, At first sight he
thought that they were the stems
of twining plants which were thus
ascending the trees; but he after-
wards found that they were the

aérial roots of a Philodendron
which grew on the branches above.
These roots therefore seem to be
true twiners, though they use
their powers to descend, instead of
to ascend like twining plant.
The aériul roots of some other
species of Philodendron hang
vertically downwards, sometimes
for a length of more than fifty feet.

Cuar. V. CONCLUDING BEMARKS. 189

Concluding Remarks on Climbing Plants.

Plants become climbers, in order, as it may be
presumed, to reach the light, and to expose a large
surface of their 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. Hence, no doubt, it
arises that there are so many climbing plants in all
quarters of the world, belonging to so many different
orders. These plants have been arranged under four
classes, disregarding those which merely scramble over
bushes without any special aid. Hook-climbers are
the least efficient of all, at least in our temperate
countries, and can climb only in the midst of an
entangled mass of vegetation. Root-climbers are
excellently adapted to ascend naked faces of rock
or trunks of trees; when, however, they climb trunks
they are compelled to keep much in the shade;
they cannot pass from branch to branch and thus cover
the whole summit of a tree, for their rootlets require
long-continued and close contact with a steady surface
in order to adhere. The two great classes of twiners
and of plants with sensitive organs, namely, leaf-
climbers and tendril-bearers taken together, far exceed
in number and in the perfection of their mechanism the
climbers of the two first classes. Those which have
the power of spontaneously revolving and of grasping
objects with which they come in contact, easily pass

190 CONCLUDING REMARKS. Cuap. V.

from branch to branch, and securely ramble over a
wide, sun-lit surface.

The divisions containing twining plants, leaf-climbers,
and tendril-bearers graduate to a certain extent into
one another, and nearly all have the same remarkable
power of spontaneously revolving. Does this grada-
tion, it may be asked, indicate that plants belonging
to one subdivision have actually passed during the
lapse of ages, or can pass, from one state to the other?
Has, for instance, any tendril-bearing plant assumed
its present structure without having previously existed
as a leaf-climber or a twiner? If we consider leaf:
climbers alone, the idea that they were primordially
twiners is forcibly suggested. The. internodes of
all, without exception, revolve in exactly the same
manner as twiners; some few can still twine well, and
many others in an imperfect manner. Several leaf-
climbing genera are closely allied.to other genera
which are simple twiners. It should also be observed,
that the possession of leaves with sensitive petioles,
and with the consequent power of clasping an object,
would be of comparatively little. use to a plant,
unless associated with revolving internodes, by which
the leaves are brought into contact with a support;
although no doubt a scrambling plant would be apt,
as Professor Jaeger has remarked, to rest on other plants
by its leaves. “On the other hand, revolving inter-
nodes, without any other aid, suffice to give the power
of climbing; so that it seems probable that leaf-
elimbers were in most cases at first twiners, and subse-

Cuap. V. CONCLUDING REMARKS, 191

quently became capable of grasping a support ; and this,
as we shall presently see, is a great additional advantage.

From analogous reasons, it is probable that all
tendril-bearers were primordially twiners, that is, are
the descendants of plants having this power and habit.
For the internodes of the majority revolve; and, in a
few species, the flexible stem still retains the capacity
of spirally twining round an upright stick. Tendril-
bearers have undergone much more modification than
leaf-climbers; hence it is not surprising that their
supposed primordial habits of revolving and twining
have been more frequently lost or modified than in
the case of leaf-climbers. The three great tendril-
bearing families in which this loss has occurred in the
most marked manner, are the Cucurbitaces, Passi-
floracese, and Vitaceee. In the first, the internodes
revolve; but I have heard of no twining form, with
the exception (according to Palm, p. 29. 52) of Momor-
dica balsamina, and this is only an imperfect twiner.
In the two other families I can hear of no twiners;
and the internodes rarely have the power of revolving,
this power being confined to the tendrils. The inter-
nodes, however, of Passiflora gracilis have the power
in a perfect manner, and those of the common Vine in
an imperfect degree: so that at least a trace of the
supposed primordial habit has been retained by some
members of all the larger tendril-bearing groups.

On the view here given, it may be asked, Why have
the species which were aboriginally twiners been con-
verted in so many groups into leaf-climbers or tendril-

192 CONCLUDING REMARKS. Cuap. V.

bearers? Of what advantage has this been to them?
Why did they not remain simple twiners? We can
see several reasons. It might be an advantage to a
plant to acquire a thicker stem, with short internodes
bearing many or large leaves; and such stems are ill
fitted for twining. Any one who will look during
windy weather at twining plants will see that they are
easily blown from their support; not so with tendril-
bearers or leaf-climbers, for they quickly and firmly
grasp their support by a much more efficient kind of
movement. In those plants which still twine, but at
the same time possess tendrils or sensitive petioles, as
some species of Bignonia, Clematis, and Tropxolum,
it can readily be observed how incomparably better
they grasp an upright stick than do simple twiners.
Tendrils, from possessing this power of grasping
an object, can be made long and thin; so that
little organic matter is expended in their develop-
ment, and yet they sweep a wide circle in search
of a support. Tendril-bearers can, from their first
growth, ascend along the outer branches of any neigh-
bouring bush, and they are thus always fully exposed
to the light; twiners, on the contrary, are best fitted
to ascend bare stems, and generally have to start in
the shade. Within tall and dense tropical forests,
twining plants would probably succeed better than
most kinds of tendril-bearers; but the majority of
twiners, at least in our temperate regions, from the
nature of their revolving movement, cannot ascend
thick trunks, whereas this can be affected by tendril-

Cuar. V. CONCLUDING REMARES. 193

bearers if the trunks are branched or bear twigs, and
by some species if the bark is rugged.

The advantage gained by climbing is to reach the
light and free air with as little expenditure of organic
matter as possible; now, with twining plants, the stem
is much longer than is absolutely necessary; for
instance, I measured the stem of a kidney-bean, which
had ascended exactly two feet in height, and it was
three feet in length: the stem of a pea, on the other
hand, which had ascended, to the same height by the
aid of its tendrils, was but little longer than the height
reached. That this saving of the stem is really an
advantage to climbing plants, I infer from the species
that still twine but are aided by clasping petioles or
tendrils, generally making more open spires than
those made by simple twiners. Moreover, the plants
thus aided, after taking one or two turns in one direc-
tion, generally ascend for a space straight, and then
reverse the direction of their spire. By this means
they ascend to a considerably greater height, with the
same length of stem, than would otherwise have been
possible ; and they do this with safety, as they secure
themselves at intervals by their clasping petioles or
tendrils.

We have seen that tendrils consist of various organs
in a modified state, namely, leaves, flower-peduncles,
branches, and perhaps stipules. With respect to
leaves, the evidence of their modification is ample.
In young plants of Bignonia the lower leaves often
remain quite unchanged, whilst the upper ones have

194 CONCLUDING REMARKS. Cuar. V.

their. terminal leaflets converted into perfect tendrils ;
in Eccremocarpus I have seen a single lateral branch
of a tendril replaced by a perfect leaflet; in Vicia
sativa, on the other hand, leaflets are sometimes
replaced by tendril-branches; and many other such
cases could be given. But he who believes in the
slow modification of species will not be content simply
to ascertain the homological nature of different. kinds
of tendrils; he will wish to learn, as far as is’ possible,
by what actual steps leaves, flower-peduncles, &c., have
had their functions wholly changed, and have come to
serve merely as prehensile organs.

In the whole group of leaf-climbers abundant
evidence has been given that an organ, still subserv-
ing the functions of a leaf, may become sensitive to a
touch, and thus grasp an adjoiming object. With
several leaf-climbers the true leaves spontaneously
revolve; and their petioles, after clasping a support
grow thicker and stronger. We thus see that leaves
may acquire all. the leading and characteristic qualities
of tendrils, namely, sensitiveness, spontaneous move-
ment, and subsequently increased strength. If their
blades or laminz were to abort, they would form true
tendrils. And of this process of abortion we can follow
every step, until no trace of the original nature of
the tendril is left. In Mutisia clematis, the tendril, in
shape and colour, closely resembles the petiole of one
of the ordinary leaves, together with the midribs of the
leaflets, but vestiges of the amine are still occasionally
retained. In four genera of the Fumariacee we cap

Juap. V. CONCLUDING REMARKS. 195

follow the whole process of transformation. The termi-
nal leaflets of the leaf-climbing Fumaria officinalis are
not smaller than the other leaflets; those of the leaf-
climbing Adlumia cirrhosa are greatly reduced; those
of Corydalis claviculata (a plant which may indifferently
be called a leaf-climber or a tendril-bearer) are either
reduced to microscopical dimensions or have their
blades wholly aborted, so that this plant is actually in
a state of transition; and, finally, in the Dicentra the
tendrils are perfectly characterized. If, therefore, we
could behold at the same time all the progenitors of
Dicentra, we should almost certainly see a series like
that now exhibited by the above-named three genera.
In Lropexolum tricolorum we have another kind of
passage ; for the leaves which are first formed on the
young stems are entirely destitute of lamine, and
must be called tendrils, whilst the later formed leaves
have well-developed lamin. In all cases the acquire-
ment of sensitiveness by the mid-ribs of the leaves
appears to stand in some close relation with the abor-
tion of their laminz or blades.

On the view here given, leaf-climbers were primor-
dially twiners, and tendril-bearers (when formed of
modified leaves) were primordially leaf-climbers. The
latter, therefore, are intermediate in nature between
twiners and tendril-bearers, and ought to be related to
both. This is the case: thus the several leaf-climbing
species of the Antirrhine, of Solanum, Cocculus, and
Gloriosa, have within the same family and even within
the same genus, relatives which are twiners. In the.

196 CONCLUDING REMARKS, Cuap. V.

genus Mikania, there are leaf-climbing and twining
species. The leaf-climbing species of Clematis are
very closely allied to the tendril-bearing Naravelia.
The Fumariacee include closely allied genera which are
leaf-climbers and tendril-bearers. Lastly, a species of
Bignonia is at the same time both a leaf-climber and
a tendril-bearer; and other closely allied species are
twiners.

Tendrils of another kind consist of modified flower-
peduncles. In this case we likewise have many in-
teresting transitional states. The common Vine (not
to mention the Cardiospermum) gives us every possible
gradation between a perfectly developed tendril and a
flower-peduncle covered with flowers, yet furnished with
a branch, forming the flower-tendril. When the latter
itself bears a few flowers, as we know sometimes is
the case, and still retains the power of clasping a
support, we see an early condition of all those tendrils
which have been formed by the modification of flower-
peduncles.

According to Mohl and others, some tendrils consist
of modified branches: I have not observed any such
cases, and know nothing of their transitional states,
but these have been fully described by Fritz Miller.
The genus Lophospermum also shows us how such a
transition is possible; for its branches spontaneously
revolve and are sensitive to contact. Hence, if the
leaves on some ofthe branches of the Lophospermum
were to abort, these branches would be converted
into true tendrils. Nor is there anything improbable

Cuar. V. CONCLUDING REMARKS, 197

in certain branches alone being thus modified, whilst
others remained unaltered; for we have seen with cer-
tain varieties of Phaseolus, that some of the branches
are thin, flexible, and twine, whilst other branches
on the same plant are stiff and have no such power.
If we inquire ‘how a petiole, a branch or flower-
peduncle first became sensitive to a touch, and
acquired the power of bending towards the touched
side, we get no certain answer. Nevertheless an ob-
servation by Hofmeister* well deserves attention,
namely, that the shoots and leaves of all plants, whilst
young, move after being shaken. Kerner also finds, as
we have seen, that the flower-peduncles of a large
number of plants, if shaken or gently rubbed bend to
this side. And it is young petioles and tendrils,
whatever their homological nature may be, which
move on being touched. It thus appears that climbing
plants have utilized and perfected a widely distributed
and incipient capacity, which capacity, as far as we
can see, is of no service to ordinary plants. If we
further inquire how the stems, petioles, tendrils, and
flower-peduncles of climbing plants: first acquired
their power of spontaneously revolving, or, to speak
more accurately, of successively bending to all points
of the compass, we are again silenced, or at most can
only remark that the power of moving, both spon-
taneously and from various stimulants, is far more

i ee Ss Supe ra a a

* Quoted by Cohn, in his hand]. der Schlesischen Gesell.
remarkable memoir, “Contractile 1861, Heft i. s. 35.
Gewebe im Pflanzenreiche,” * Ab-

Cuap, V.

198 CONCLUDING REMARKS.

zommon with plants, than is generally supposed to be
the case by those who have not attended to the subject.
I have given one remarkable instance, namely that of
the Maurandia semperflorens, the young flower-peduncles
of which spontaneously revolve in very small circles,
and bend when gently rubbed to the touched side;
yet this plant certainly does not profit by these two
feebly developed powers. A rigorous examination of
other young plants would probably show slight spon-
taneous movements in their stems, petioles or pe-
duncles, as well as sensitiveness to a touch.* We see
at least that the Maurandia might, by a little aug-
mentation of the powers which it already possesses,
come first to grasp a support by its flower-peduncles,
and then, by the abortion of some of its flowers (as with
Vitis or Cardiospermum), acquire perfect tendrils.
There is one other interesting point. which deserves
notice. We have seen that some tendrils owe their
origin to modified leaves, and others to modified flower-
peduncles; so that some are foliar and others axial
in their nature. It might therefore have been expected
that they would have presented some difference in
function. This is not the case. On the contrary, they

* Such slight spontaneous shown inrelationtoour present sub-

movements, I now find, have been
for some time known to occur,
for instance with the flower-stems
of Brassica napus and with the
leaves of many plants: Sachs’
* Text-Book of Botany’ 1875, pp.
766, 785, Fritz Miller also has

ject (‘Jenaischen Zeitschrift,’ Bd.
V. Heft 2, p. 133) that the stems,
whilst young, of an Alisma and
of a Linum are continually
performing slight movements to
all points of the compass, like
those of climbing plants,

Cnar. V. CONCLUDING REMARKS. 199

present the most complete identity in their several
characteristic powers. Tendrils of both kinds sponta-
neously revolve at about the same rate. Both, when
touched, bend quickly to the touched side, and after-
wards recover themselves and are able to act again.
In both the sensitiveness is either confined to one side
or extends all round the tendril. Both are either
attracted or repelled by the light. The latter property
is seen in the foliar tendrils of Bignonia capreolata
and in the axial tendrils of Ampelopsis. The tips
of the tendrils in these two plants become, after con-
tact, enlarged into discs, which are at first adhesive
by the secretion of some cement. Tendrils of both
kinds, soon after grasping a support, contract spirally ;
they then increase greatly in thickness and strength.
When we add to these several points of identity the
fact that the petiole of Solanum jasminoides, after
it has clasped a support, assumes one of the most
characteristic features of the axis, namely, a closed ring
of woody vessels, we can hardly avoid asking, whether
the difference between foliar and axial organs can be
of so fundamental a nature as is generally supposed ? *
’ We have attempted to trace some of the stages in
the genesis of climbing plants. But, during the
endless fluctuations of the conditions of life to which
all organic beings have been exposed, it might be
expected that some climbing plants would have lost

* Mr. Herbert Spencer has much force that there is no fun
recently argued (‘Principles of damental distinction between the
Biology,’ 1865, p. 87 et seg.) with _ foliar and axial organs of plants.

200 CONCLUDING REMARKS. Cuar. V.

the habit of climbing. In the cases given of certain
South African plants belonging to great twining fami-
lies, which in their native country never twine, but
reassume this habit when cultivated in England, we
have a case in point. In the leaf-climbing Clematis
flammula, and in the tendril-bearing Vine, we see no
loss in the power of climbing, but only a remnant of the
revolying power which is indispensable to all twiners,
and is so common as well as so advantageous to most
climbers. In Tecoma radicans, one of the Bignoniacee,
we see a last. and doubtful trace of the power of
revolving.

With respect to the abortion of tendrils, certain
cultivated varieties of Cucurbita pepo have, according
to Naudin,* either quite lost these organs or bear
semi-monstrous representatives of them. In my
limited experience, I have met with only one ap-
parent instance of their natural suppression, namely,
in the common bean. All the other species of Vicia,
I believe, bear tendrils; but the bean is stiff enough
to support its own stem, and in this species, at the
end of the petiole, where, according to analogy, a ten-
dril ought to have existed, a small pointed filament
projects, about a third of an inch in length, and which
is probably the rudiment of a tendril. This may be
the more safely inferred, as in young and unhealthy
specimens of other tendril-bearing plants similar rudi-
ments may occasionally be observed. In the bean

* Annales des Sc. Nat. 4th series, Bot. tom. vi. 1856, p. 31.

Cuar. V. CONCLUDING REMARKS. 201

these filaments are variable in shape, as is so fre-
quently the case with rudimentary organs; they are
either cylindrical, or foliaceous, or are deeply furrowed
on the upper surface. They have not retained any
vestige of the power of revolving. It is a curious
fact, that many of these filaments, when foliaceous,
have on their lower surfaces, dark-coloured glands like
those on the stipules, which excrete a sweet fluid; so
that these rudiments have been feebly utilized.

One other analogous case, though hypothetical, is
worth giving. Nearly all the species of Lathyrus
possesses tendrils; but L. néssolza is destitute of them.
This plant has leaves, which must have struck every
one with surprise who has noticed them, for they are
quite unlike those of all common papilionaceous
plants, and resemble those of a grass. In another
species, L. aphaca, the tendril, which is not highly
developed (for it is unbranched, and has no spon-
taneous revolving-power), replaces the leaves, the
latter being replaced in function by large stipules.
Now if we suppose the tendrils of L. aphaca to become
flattened and foliaceous, like the little rudimentary
tendrils of the bean, and the large stipules to become
at the same time reduced in size, from not being any
longer wanted, we should have the exact counterpart
of ZL. nissolia, and its curious leaves are at once
rendered intelligible to us.

It may be added, as serving to sum up the foregoing
views on the origin of tendril-bearing plants, that L.
nissolia is probably descended from a plant which was

202 CONCLUDING REMARKS, Cuar. V.

primordially a twiner ; this then became a leaf-climber,
the leaves being afterwards converted by degrees into
tendrils, with the stipules greatly increased in size
through the law of compensation.* After a time the
tendrils lost their branches and became simple; they
then lost their revolving-power (in which state they
would have resembled the tendrils of the existing
L. aphaca), and afterwards losing their prehensile
power and becoming foliaceous would no longer be
thus designated. In this last stage (that of the exist-
ing L. nissolia) the former tendrils would reassume
their original function of leaves, and the stipules which
were recently much developed being no longer wanted,
would decrease in size. If species become modified in
the course of ages, as almost all naturalists now admit,
we may conclude that L. nissolia has passed through a
series of changes, in some degree like those here
indicated.

The most interesting point in the natural history of
climbing plants is the various kinds of movement
which they display in manifest relation to their wants.
The most different organs—stems, branches, flower-
peduncles, petioles, mid-ribs of the leaf and leaflets,
and apparently aérial roots—all possess this power.

The first action of a tendril is to place itself in a
proper position. For instance, the tendril of Cobea

~ Moquin-Tandon (Eléments de _ this nature was suddenly effected ;
Tératologie, 1841, p. 156) gives for the leaves completely dis-
the case of a monstrous bean, in appeared and the stipules grew to
which a case of compensation of an enormous size.

Cuar. V. CONCLUDING REMARKS. 203

first rises vertically up, with its branches divergent
and with the terminal hooks turned outwards; the
young shoot at the extremity of the stem is at the
same time bent to one side, so as to be out of the way.
The young leaves of Clematis, on the other hand,
prepare for action by temporarily curving themselves
downwards, so as to serve as grapnels.

Secondly, if a twining plant or a tendril gets by
any accident into an inclined position, it soon bends
upwards, though secluded from the light. The guid-
ing stimulus no doubt is the attraction of gravity, as
Andrew Knight showed to be the case with germinat-
ing plants. Ifa shoot of any ordinary plant be placed
in an inclined position in a glass of water in the dark,
the extremity will, in a few hours, bend upwards; and
if the position of the shoot be then reversed, the
downward-bent shoot reverses its curvature; but if
the stolon of a strawberry, which has no tendency to
grow upwards, be thus treated, it will curve downwards
in the direction of, instead of in opposition to, the
force of gravity. As with the strawberry, so it is
generally with the twining shoots of the Hibbertia
dentata, which climbs laterally from bush to bush; for
these shoots, if placed in a position inclined downwards,
show little and sometimes no tendency to curve up-
wards,

Thirdly, climbing plants, like other plants, bend
towards the light by a movement closely analogous to
the incurvation which causes them to revolve, so that
their revolving movementis often accelerated or retarded

204 CONCLUDING REMARKS, Cuapr. V.

in travelling to or from the light. On the other
hand, in a few instances tendrils bend towards the
dark.

Fourthly, we have the spontanevus revolving move-
ment which is independent of any outward stimulus,
but is contingent on the youth of the part, and on
vigorous health; and this again of course depends on
a proper temperature and other favourable conditions
of life.

Fifthly, tendrils, whatever their homological nature
may be, and the petioles or tips of the leaves of leaf-
climbers, and apparently certain roots, all have the
power of movement when touched, and bend quickly
towards the touched side. Extremely slight pressure
often suffices. If the pressure be not permanent, the
part in question straightens itself and is again ready
to bend on being touched.

Sixthly, and lastly, tendrils, soon after clasping a
support, but not after a mere temporary curvature,
contract spirally. Ifthey have not come into contact
with any object, they ultimately contract spirally, after
ceasing to revolve; but in this case the movement is
useless, and occurs only after a considerable lapse of
time.

With respect to the means by which these various
movements are effected, there can be little doubt from
the researches of Sachs and H. de Vries, that they are
due to unequal growth; but from the reasons already
assigned, I cannot believe that this explanation applies
to the rapid movements from a delicate touch.

Crup. V. CONCLUDING REMARKS. 205

Finally, climbing plants are sufficiently numerous to
form a conspicuous feature in the vegetable kingdom,
more especially in tropical forests. America, which so
abounds with arboreal animals, as Mr. Bates remarks,
likewise abounds according to Mohl and Palm with
climbing plants; and of the tendril-bearing plants
examined by me, the highest developed kinds are
natives of this grand continent, namely, the several
species of Bignonia, Eccremocarpus, Cobxa, and Ampe-
lopsis. But even in the thickets of our temperate
regions the number of climbing species and individuals
is considerable, as will be found by counting them.
They belong to many and widely different orders. To
gain some rude idea of their distribution in the vegetable
series, I marked, from the lists given by Mohl and Palm
(adding a few myself, and a competent botanist, no
doubt, could have added many more), all those families
in Lindley’s ‘Vegetable Kingdom’ which include
twiners, leaf-climbers, or tendril-bearers. Lindley
divides Phanerogamic plants into fifty-nine Alliances ;
of these, no less than thirty-five include climbing plants
of the above kinds, hook and root-climbers being ex-
eluded. To these a few Cryptogamic plants must be
added. When we reflect on the wide separation of these
plants in the series, and when we know that in some of
the largest, well-defined orders, such as the Composite,
Rubiaceze, Scrophulariacez, Liliacee, &., species in
only two or three genera have the power of climbing,
the conclusion is forced on our minds that the capacity of
revolving, on which most climbers depend, is inherent,

206 CONCLUDING REMARKS. Cuap. V.

though undeveloped, in almost every plant in the
vegetable kingdom.

It has often been vaguely asserted that plants are
distinguished from animals by not having the power
of movement. It should rather be said that plants
acquire and display this power only when it is of some
advantage to them; this being of comparatively rare
occurrence, as they are affixed to the ground, and food
is brought to them by the air and rain. We see
how high in the scale of organization a plant may
rise, when we look at one of the more perfect tendril-
bearers. It first places its tendrils ready for action,
as a polypus places its tentacula. If the tendril be
displaced, it is acted on by the force of gravity and
rights itself. It is acted on by the light, and bends
towards or from it, or disregards it, whichever may be
most advantageous. During several days the tendrils
or internodes, or both, spontaneously revolve with a
steady motion. The tendril strikes some object, and
quickly curls round and firmly grasps it. In the
course of some hours it contracts into a spire, dragging
up the stem, and forming an excellent spring. All
movements now cease. By growth the tissues soon
become wonderfully strong and durable. The tendril
has done its work, and has done it in an admirable
manner.

INDEX.

Abortion of tendrils, 206

Adlumia cirrhosa, 76

Advantages gained by climbing, 189

Alisma, spontaneous movement of, 198

Anguria Warscewiczii, 136 [205

America, number of climbing plants of,

Ampelopsis hederacea, 144

Bates, Mr., on number of arboreal
animals in America, 205 [202

Bean, common, abortion of tendrils, 200,

Bignonia, various species of, bearing
tendrils, 86

Brassica napus, spontaneous movement
of peduncles, 198

Bryonia dioicz, 131, 136

Caoutchouc secreted by roots of Ficus
repens, 186

Cardiospermum halicacabum, 150

Ceropegia Gardnerii, 6

—— —, manner of twining, 20

—, a species which has lost the
power of twining in South Africa, 42

Cissus discolor, 143

Clematis, various
climbers, 46

Cobza scandens, 106

Combretum, 41

Corydalis claviculata, 121

Cucurbitacez, nature of tendrils, 127

Cucurbita pepo, aborted tendrils, 200

Cuscuta, stems of, irritable, 17, 71

Dicentra thalictrifolia, 124

Dipladenia, furnished with hooks, 184

Discs, adhesive, developed by tendrils,
94, 100, 135, 136, 145, 179

Dutrochet, reference to papers on
climbing plants, 1

Eccremocarpus scaber, 103

Echinocystis lobata, 128

Ferns, twining, 38

Ficus repens, a root-climber, 185

Flagellaria Indica, 79

Flower-peduncles of Maurandia sensi-
tive, and revolve spontaneously, 67

Fumaria officinalis, 75

Galium aparine, a hook-climber, 183

Gradations of structure leading to the
develoy ment of perfect tendrils, 195,
196

species of, leaf-

Gray, Asa, reference to paper on
tendrils of Cucurbitacez, 1

on tendrils of Passiflora, 154

Sicyos, 172

— on Rosa setigera, 184

Gloriosa Plantii, 78

Hanburya Mexicana, 134

Harvey, Prof., on the loss of power of
twining, 42

Hedeta helix, 185, 188

Hibbertia dentata, 35 [203

, shoots of, turn downwards,

Hofmeister, on irritability of young
petioles, 197

Hook-climbers, 183

Hop, powers of twining, 2

Hoya carnosa, 6, 43, 185

Humulus lupulus, 2

India-rubber secreted by roots of Ficus
repens, 186

Ipomeea argyrzoides, 42

Ivy, 185, 188 {183, 199

Jaeger, Prof. G., on climbing plants,

Kerner, on the irritability of fower-
peduncles, 197

Lathyrus aphaca, 115

» probable manner of de-

velopment of its tendrils, 201

, grandiflorus, 116

nissolia, grass-like leaves replacing
tendrils, 201

Leaves, position of, on twining plants, 19

Leaf-climbers, 45

— summary on, 81

climb more securely than
twiners, 192

Léon, M., on a variety of Phaseolus, 42

, on spiral contraction of ten-

drils, 166

Light, action on twining plants, 40

, avoidance of, by tendrils, 98, 105,
110, 138, 145, 175

Linum, spontaneous movement of, 198

Loasa aurantiaca, 34

Lophospermum scandens, 71

Lygodium articulatum, 38

M‘Nab, Dr., on Ampelopsis Veitchii, 146

Marcgravia, a root-climber, 185, 188

Masters, Dr. M., on torsion, 10

208

Masters, Dr. M., on the woody vessels of
petioles, 75

Maurandia, a leaf-climber, 66

Mikania scandens, 33

Mohl, Hugo, reference to work of, 1

Moquin-Tandon, on the abc rtion of the
leaves of the bean, 202

Miller, Fritz, on the structure of the
wood of climbing plants, 44

on plants scrambling ever

other plants, 183

on the development of

branches into tendrils, 84

on roots of Philodendron,

188

on the spontaneous move-
ments of certain plants, 198

Mutisia clematis, 116

Naudin on abortion of tendrils, 200

Nepenthes, 86

Nutation, revolving, 11

Ophioglossum Japonicum, 77

Palm, reference to work of, 1

Passiflora acerifolia, 154

gracilis, 153

punctata, 156

quadrangularis, 157

Paullinia, 153

Pea, common, 112

Peduncles of Maurandia sensitive and
revolve spontaneously, 67

Phaseolus, torsion of axes, 9

—-, non-twining variety, 42

Philodendron, roots of, 188

Pisum sativum, 112

Polygonum convolvulus, 41

Rhodochiton volubile, 70

Roots acting like tendrils, 188

Root-climbers, 185

Rosa setigera, shoots bend from the
light, 184

Rubus australis, 183

Sachs, Prof., on torsion, 9

on cause of revolving move-

ment, 22

on tendrils adapted to clasp
supports of different thickness, 176
on cause of movement of ten-
drils when touched, 180
Sensitiveness of tendrils, nature of, 197

INDEX.

Serjania, 152
Smilax aspera, 118, 184
Spencer, Herbert, on the relation of axial
and foliar organs, 199
Spiller, Mr., on the oxidation of india-
rubber, 187 ri
Spruce, Mr., on Marcgravia, 185
Solanum dulcamara, 34, 43
jasminoides, 72
Spiral contraction of tendrils, 158
Summary on twining plants, 39
Summary on leaf-climbers, 81
Summary on the movements of tendrils,
169, 202 [13
Summit of twining plants, often hooked,
Support, thickness of, round which
plants can twine, 22, 36
, thickness of, which can be em-
braced by tendrils, 176
Tacsonia manicata, 158
Tamus elephantipes, 41
Tecoma radicans, 43, 185
Tendrils, history of our knowledge of, 85
——, spiral contraction of, 158 =~
——, summary on, 169, 202 pao
, cause of movement when touched,
Tendril-bearers climb more securely
than twiners, 192
Tendrils, abortion of, 200
Torsion of the axes of twining plants, 7
Tropzolum, various species of, leaf-
climbers, 60
Twining plants, 2
, shoots of, sometimes sponta-
neously become spiral, 17
table of rates of revolution
of various species, 24
anomalous cases of, 41
Twisting of the axes of twining plants, 7
Vanilla aromatica, 188
Vine, common, 137
Virginian creeper, 144
Vries, H. de, on torsion, 9
—- on cause of revolving movement, 22
— on spiral contraction of ten-
drils, 160, 165
cause of im
drils, 180
Vitis vinifera, 137
Zanonia Indica, 136

ements of ten-

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country. All lovers of nature will unite in Eoanking Mr. Darwin for the new and
interesting light he has thrown upon a subject so long overlooked, yet so fall of
interest and instruction, as the structure and the labors of the earth-worm.'’—
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“ Respecting worms as among the most usefal portions of animate nature,
Dr. Darwin relates, in this remarkable book, their structure and habits, the part
they have played in the burial of ancient buildings and the denudation of the
land, in the disintegration of rocks, the preparation of soil for the growth of
plants, and in the natural history of the world.”"— Boston Advertiser.

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THE SUN. By C.A. Young, Ph. D., LL. D., Professor of Astronomy in the College
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ILLUSIONS: A Psychological Study. By James StLty, author of “ Sensa-
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SIGHT: An Exposition of the Principles of Monocular and Binocular Vision.
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THE CRAYFISH. An Introduction to the Study of Zodlogy. By Professor
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THE HUMAN SPECIES. By A. Dz QuatreraceEs, Professor of Anthro-
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EDUCATION AS A SCIENCE. By ALEXANDER Barn, LL.D. 12mo, cloth,
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A HISTORY OF THE GROWTH OF THE STEAM-ENGINE. By
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STUDIES IN SPECTRUM ANALYSIS. By J. Norman Locxrrer, F.R.S.,
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