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Full text of "The movements and habits of climbing plants"

THE 



MOVEMENTS AND HABITS 



OF 



CLIMBING PLANTS. 



BY THE SAME AUTHOR. 



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MOVEMENTS AND HABITS 



OP 



CLIMBING PLANTS. 



By CHAELES DARWIN, M.A., F.B.S., 

ETC. 



SECOND EDITION, REVISED, 



WITH ILLUSTRATIONS. 



NEW YORK : 
D. APPLETON AND COMPANY, 

i, 3, and 5 BOND STREET. 
i883. 



PREFACE. 

This 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 Muller, 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 Wurzburg/ 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 



n 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, 
Cobsea, 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. 



CHAPTER I. 

Twining Plants. 

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 Eate of revolu- 
tion in various plants Thickness of the support round 
which plants can twine Species which revolve in an anoma- 
lous manner Pages 1-44 

CHAPTER II. 

Leaf-Climbers. 

Plants which climb by the aid of spontaneously revolving and 
sensitive petioles Clematis Tropoeolum Maurandia, flower- 
peduncles moving spontaneously and sensitive to a touch 
Kliodochiton Lophospermum, internodes sensitive Sohtnum, 
thickening of the clasped petioles Fumaria Adlumia 
Plants which climb by the aid of their produced midribs 
Gloriosa Flagellaria Nepenthes Summary on leaf- 
chmbers 45-83 

CHAPTER III. 

Tendril-Bearebs. 

Nature of tendrils Bignoniaceje, 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 
Polemoniacejb Cobcea scandens, much branched and 



nil CONTENTS. 

hooked tendrils, their manner of action Leguminos^; 
Composites Smilacejs Smilax aspera, its inefficient 
tendrils Fumariacees Corydalis claviculata, its state 
intermediate between that of a leaf-climber and a tendril- 
bearer Pages 84-126 

CHAPTER IV. 

Tendril-Bearers continued. 

Cucurbitace-ej Homologous nature of the tendrils Echino- 
cystis lohata, 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 Vitacejs 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 Sapindacees Passifloracees Passiflora gracilis 
Eapid 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-Climbers. Concluding 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 



index 207 



THE 

MOVEMENTS AND HABITS 

OP 

CLIMBING PLANTS. 



-*o- 



CHAPTER I. 

Twining Plants. 

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 revolution in various plants 
Thickness of 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, was published only a few weeks 

1858, p. 98. before Mold's. See also The Ve- 

t Ludwig H. Palm, ' Ueber das getable Cell' (translated by Hen- 

Winden der Pflanzen;' Hugo von frey), by H. von Mohl, p. 147 to 

Mohl, ' Ueber den Bau und das end. 

Wiiiden dor Ranken und Schling- % " Des Mouvemcnts revolutifd 



2 TWINING PLANTS. Chap. 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, 



apontanes/'&c./ComptesRendus,' ckerches sur la Volubilite des 
torn. xvii. (1843) p. 989; "Re- Tiges,"<frc.,tom.xix.(1844)p.295. 



Chap. 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, If 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 
tliird circle was performed in the evening in a little over 



4 TWINING PLANTS. Chap. I. 

3 hrs. 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 3 hrs. I should add that the temperature 
of the room varied only a little. The shoot had now 
grown 3 J 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 2 hrs. 30 m. 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. 31 m. ; 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 



Chap. I. TWINING PLANTS. 5 

segment of a circle. After the seventeenth revolution 
the internode had grown from If to 6 inches in length, 
and carried an internode 1J inch long, which was 
just perceptibly moving ; and this carried a very minute 
ultimate internode. After the twenty-first revolution, 
the penultimate internode was 2J inches long, and 
probably revolved in a period of about three hours. 
At the twenty-seventh revolution the lower and still 
moving internode was S, the penultimate 3J, and 
the ultimate 2 \ 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 



b TWINING PLANTS. Chap. L 

were at the same time revolving ; and this was the case 
with most of the plants observed by me. With all, if in 
fall 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 Gardnerii, 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. 45 m. 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 long 
shoot sweeping this grand cricle, night and day, in 
search of some object round which to twine. 



Chap. 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 a time. 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. Chap. I 

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 lohata, Bignonia capreolata, Eecremocarpus scaler, 
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 Leon,* 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 Leon (p. 356), is 
the case with all the internodes of a certain variety of 
Phaseolus multiflorus. 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. Ill) that when a stem twines 
round a smooth cylindrical stick, it does not become 



* 'Bull. Bet Soc. de France,' torn. v. 1858, p. 356. 



Chap. I. 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 it has ceased or begun to cease in 

ably discussed and explained by the inner layers." 

H. de Vries, 'Arbeiten des Bot. f Professor Asa Gray has re- 

Instituts in Wurzburg,' Heft iii. marked to me, in a letter, that in 

pp. 331,336. See also Sachs ('Text- Thuja occidentalis the twisting of 

Book of Botany,' English transla- the bark is very conspicuous. The 

tion, 1875, p. 770), who concludes twist is generally to the right of 

" that torsion is the result of growth the observer; but, in noticing 

continuing in the outer layers after about a hundred trunks, four ox 



10 



TWINING PLANTS. 



Chap. L 



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 allowing 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. 
Tbe 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 
steins of many plants occasionally 
become spirally twisted in a 
monstrous manner ; and after my 
paper was read before tbe 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 th 
stem. 



Chap. 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 a coloured 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. Chap. 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. JSTow, 
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 to the 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 



Chap. 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 Asclepiadacese. The hooked tip, in all the 
cases observed by me, viz. in Ceropegia, Sphserostema, 
Clerodendron, Wistaria, Stephania, Akebia, and Sipho- 
meris, has exactly the same kind of movement as the 



14 TWINING PLANTS. Chap. 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 hrachypoda 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 Vrics (ibid. p. 3.>7) : he 
2nd 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 nutation.' 



Chap. 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. Chap. 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 Mold's interesting 
treatise, this view seemed to me so probable that I 
tested it in every way that I could, but always with 
a negative 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, Sphserostema, 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) by a 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. 



Chap. 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 Alebia, 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 Cerojpegia, revolved in 6 hrs., 



t Dr. H. de Vries states (ibid. p. 322) that the stem of Cuscuta is 
irritable like a tendril. 
2 



18 TWINING PLANTS. Ch^p. L 

but took 9 hrs. 30 m. to make one complete spire round 
a stick ; Aristoloehia gigas revolved in about 5 hrs., but 
took 9 hrs. 15 m. to complete its spire. This, I 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 Geropegia, 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. 



Ciiap. I. 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 Eendus, 1844, torn. xix. p. 295, and Annales des Sc. Nat. 
3rd series, Bot., torn. ii. p. 163. 



20 TWINING PLANTS. Chap. I 

who found different individuals of Solatium 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 2J inches from the extremity of the penulti- 
mate inter node ; 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 



Chap. 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. Chap. 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 Yries, 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. 135), 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 



Ciia.p. I. 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 Hibhertia dentata, showed but little 
tendency to turn upwards. In other cases, as with the 
Cryftostegia 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 



24 



TWINING PLANTS. 



Chap. L 



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

The Bate of Revolution of various Twining Plants. 

(ACOTYLEDONS.) 

Lygodium scandens (Polypodiacese) moves against the sun. 



June 18, 1st circle was made in 

18, 2nd 

19, 3rd 
19, 4th 

20, 5th 



a 



























>} 



a 



>} 



a 



a 



a 



it 



H. M. 

6 

6 15 (late in evening) 

5 32 (very hot day) 

5 (very hot day) 

6 



Lygodium articidatum moves against the sun. 



H If* 



July 19, 1st circle was made in . 16 30 (shoot very young) 
20,2nd . 15 



a 



21, 3rd 

22, 4th 







>f 



)> 







)> 







t 



8 
10 30 



(Monocotyledons.) 

Buscus androgynus (Liliacea3), placed in the hot-house, moves 
against the sun. 











H. M. 


May 24, 1st circle 


was made in 


. 6 14 (shoot very younsj) 


25, 2nd 


a 


a 


a 


. 2 21 


25, 3rd 


a 


it 


it 


. 3 37 


25, 4th 


it 


a 


it 


. 3 22 


26, 5th 


a 


tt 


it 


. 2 50 


27, 6th 


u 


a 


it 


. 3 52 


27, 7th 


a 


tt 


tt 


. 4 11 



* I am much indebted to Dr. 
Hooker for having sent me many 
plants from Kew ; and to Mr. 
Veitch, of the Royal Exotic Nur- 
sery, for having generously given 
me a collection of fine specimens 



of climbing plants. Professor Asa 
Gray, Prof. Oliver, and Dr. Hooker 
have afforded me, as on many 
previous occasions, much infor- 
mation and many references. 



Chap. I. 



TWINING PLANTS. 



25 



(Monocotyledons, continued.) 
Asparagus (unnamed species from Kew) (Liliacea}) moves 
against the sun, placed in hothouse. 



H. M. 

5 
5 40 







a 







>> 







Dec. 26, 1st circle was made in 
27,2nd 

Tamtis communis (Dioscoreaceas). A young shoot from a 
tuber in a pot rjlaced in the greenhouse : follows the sun. 

II. Mi 

July, 7, 1st circle was made in . . . 3 10 

7, 2nd ... 2 38 

8,3rd ... 3 5 

8, 4th ... 2 56 
8,5th 
8,6th 

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

H. M. 

March 9, 1st circle was made in 
10, semicircle 
11, 2nd circle 
12,3rd 
13, 4th 
16, 5th 

the hothouse ; but the next day the shoot remained 
stationary. 

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

(Dicotyledons.) 

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



> 



> 















2 30 
2 30 



26 15 (shoot young) 

8 15 
11 
15 30 
14 15 

8 40 when placed in 









H. M. 


April 9, 2 circles were 


made in . 


. . 4 16 


Aug. 13, 3rd circle 


was 


n 


..20 


14,4th 








. . 2 20 


14, 5th 


>} 


a 


. . 2 16 


14, 6th 





a 


..22 


14,7th 





a 


..20 


14,8th 








..24 



26 TWINING PLANTS. Chap. I. 

(Dicotyledons, continued.) 

With the Hop a semicircle was performed, in travelling 
from the light, in 1 hr. 33 m. ; in travelling to the light, in 
1 hr. 13 m. ; difference of rate, 20 m. 

Akt-bia quinata (Lardizabalaceae), placed in hothouse, moves 
against the sun. 





H. M. 


March 17, 1st circle was made in . 


. 4 (shoot young) 


18, 2nd 


. 1 40 


18, 3rd 


. 1 30 


iy, 4tn . 


. 1 45 



>tauntonia latifolia (Lardizabalaceaa), placed in hothouse, 
moves against the sun. 

H. K 

March 28, 1st circle was made in . . 3 30 
29, 2nd . . 3 45 

Sphcerostema marmoratum (Schizandraceae) follows the sun. 

H. M. 

August 5th, 1st circle was made in about . . 24 
5th, 2nd circle was made in . . . . 18 30 

Stephania rotunda (Menispermaceae) moves against the sun. 

H. M. 

May 27, 1st circle was made in . . .55 

30, 2nd ... 7 6 

June 2, 3rd ... 5 15 

o, 4tn ... 6 28 

Thryallis brachystacnys (Malpighiaceae) moves against the sun : 
one shoot made a circle in 12 hrs., and another in 10 hrs. 30 m. ; 
but the next day, which was much colder, the first shoot took 
10 hrs. to perform only a semicircle. 

Hibbertia dentata (Dilleniacese), placed in the hothouse, fol- 
lowed the sun, and made (May 18th) a circle in 7 hrs. 20 m. ; on 
the 19 th, reversed its course, and moved against the sun, and 
made a 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 



Chap. L 



TWINING PLANTS. 



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 Drummondii (Pittosporacese) moves against the sun; 
kept in greenhouse. 

April 4, 1st circle was made in 
5, 2nd 
6, 3rd 
1 4tn 
Polygonum dumetorum (Polygonacese). 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 (Leguminosse), in greenhouse, moves 
against the sun. 



)> 



)> 



H. M. 

4 25 

8 (very cold day) 

6 25 

7 5 









H. M. 


May 13, 1st circle 


was made in . 


..35 


13,2nd 


n 


11 it ' 


. . 3 20 


16,3rd 


it 


it 11 


..25 


24,4th 


it 


)> it 


. . 3 21 


H 25,5th 


tt 





. . 2 37 


25,6th 


11 


)} it 


. . 2 35 



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

H. M. 

May, 1st circle was made in . . . .20 
it 2nd .... 1 55 
it " r d ii a a .... 1 55 

Dijpladenia urophylla (Apocynaceae) moves against the sun. 

H. jr. 

April 18, 1st circle was made in . 
19, 2nd 
30, 3rd 

ripladenia crassinoda moves against the sun. 

May 16, 1st circle was made in . . 
July 20, 2nd 
21, 3rd 



a 



it 



a 



a 



n 



tt 



a 



tt 



a 







tt 



8 





9 15 


9 40 


H. 


M. 


9 


5 


8 





8 


5 



2S TWINING PLANTS. Chap. I 

(Dicotyledons, continued.) 

Ctropegia Qardnerii (Asclepiadacese) moves against the sun. 

H. M. 

Shoot very young. 2 inches ) - . . , , . _ 

.... > 1st circle was performed in 7 5o 

in length ) r 

Shoot still young . . . 2nd 

Long shoot . 3rd 

Long shoot 4th 

Long shoot 5th 



> 






)J 


)) 


7 


> 





}) 


6 33 











5 15 


5> 








6 45 



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

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

JpomcEa purpurea (Convolvulacess) moves against the sun. 
Plant placed in room with lateral light. 

! Semicircle, from the light in 
1 hr. 14 m., to the light 
1 hr. 28 m. : difference 14 m. 
(Semicircle, from the light in 
1 hr. 17 m., to the light 1 hr. 
30 m. : difference 13 m. 

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



1st circle was made in 5 hrs. 30 m.. 
2nd circle was made in 5 hrs. 



Semicircle, from the light in 
4 hrs. 30 m., to the light 1 hr. 
m. : difference 3 hrs. 30 m. 



i Semicircle, from the light in 
3 hrs. 50 m, to the light lhr. 
30 m. -.difference 2 hrs 20 m. 

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

Convolvulus sepiura (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. 



Chap. I. TWINING PLANTS. 29 

(Dicotyledons, continued.) 

Rivea tiUcefolia (Convolvulaceae) 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 (Plumbaginacese) 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. 45 m. 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 (Jasminaceae), moves against 
the sun. A circle was made in 7 hrs. 15 m., and a second rather 
more quickly. 

Clerodendrum Thomsonii (Verbenaceae) follows the sun. 



H. M. 



April 12, 1st circle was 


made 


in . 5 45 


14,2nd 


}> 


. 3 30 


18, a semicircle 





. 5 


19, 3rd circle 


)> 


. 3 


20,4th 





. 4 20 



5 45 (shoot very young) 

[(directly after the 
plant was shaken 
on being moved) 



Tecoma jasminoides (Bignoniacese) moves against the sun. 

H. H. 

March 17, 1st circle was made in . 6 30 

19,2nd .70 

22, 3rd .8 30 (very cold day) 

24, 4th .6 45 

Tkunbergia alata (Acanthacese) moves against sun. 

April 14, 1st circle was made in . 3 20 
18, 2nd . 2 50 
18, 3rd .2 55 
18, 4th .3 55 (late in afternoon) 



30 



TWINING PLANTS. 



Chap. I. 



(Dicotyledons, continued.) 

Adhadota cydoncefolia (Acanthaceae) 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 (Compositae) moves against the sun. 

H. M. 

March 14, 1st circle was made in 3 10 

3 
3 
3 33 
2 50 

(This circle was made 
after a copious water- 
ing with cold water at 
47 Fahr. 



}) 


15, 2nd 


a 


>> 


)) 


16, 3rd 





>> 


>> 


17, 4th 


t> 





ril 


7,5th 


> 


> 



tt 



7,6th 



3t 



)) 















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



H* M 



Jan. 24, 1st circle was made in 2 55 
24, 2 circles each at an 



Early in morning, when 
the temperature of the 
house had fallen a little. 







>> 



average of 



t an) 



2 20 



25, 4th circle was made in 2 25 



Combretum purpureum revolves not quite so quickly as 0. 
argenteum. 

Loasa aurantiaca (Loasacese). Eevolutions variable in ther 
course : a plant which moved against the sun. 

H. K. 

June 20, 1st circle was made in . . . 2 37 
20,2nd 
20,3rd 
21,4th 
22,5th 
23,6th 








ltliU.C> XXX 


. . 4+ KJ % 

. . 2 13 


)} 





I) * 


..40 


a 





* 


. . 2 35 





U 


it 


. . 3 26 


ti 


n 


tt 


..35 



Chap. I. 



TWINING PLANTS. 



31 



(Dicotyledons, continued.) 
Another plant which followed the sun in its revolutions. 



July 11, 1st circle 


was made in 


11,2nd 








11,3rd 





a >} 


11,4th 





a 


12,5th 


5> 


> 



Scyphanthus elegans (Loasaceae) fo 



H. M. 

1 51 
1 46 
1 41 

1 48 

2 35 



1 



Very hot day. 



lows the sun. 



June 13, 1st circle was made in 
13,2nd 



:> 



14,3rd 
14,4th 



14, 5th 



a 



a 



> 









a 



II. X. 

1 45 
1 17 
1 36 

1 59 

2 3 



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



H. M. 



]\f ay 25, semicircle was made in 



)f 


26, 


2st circle 





30, 


2nd 





un 


B 2, 


3rd 


>y 





6, 


4th 


)> 


> 


8, 


5th 





a 


9, 


6th 


a 















i* 



if 



ii 



a 



a 



1 97 J ( sno0 * extremely 

I young) 
10 15 (shoot still young) 
8 55 
8 11 
6 8 

Taken from the 
hothouse, and 
placed in a room 
in my house. 



7 20 

8 36 



i 



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



July 7, 1st circle was made in 
8, 2nd 
y, ord 



a 



6 18 
6 53 
6 30 



Lonicera brachypoda (Caprifoliaceae) follows the sun, kept in a 
warm room in the house. 

H. M. 

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



32 TWINING PLANTS. Chap. I. 

(Dicotyledons, continued.) 

H. II. 

. .. n , . , , . ln nrt I (a distinct shoot, very 

April, 2nd circle was made in 12 20 { x , * 

[ young, on same plant) 

3rd . 7 30 

In this latter circlo, 

the semicircle from 
the light took 5 hrs. 
23 m., and to the 
light 2 hrs. 37 min. : 
difference 2 hrs 46 m. 

Aristolochia gigas (Aristolochiacese) moves against the sun. 

H. m. 

July 22, 1st circle was made in . 8 (rather young shoot) 
23, 2nd .7 15 

24, 3rd .50 (about) 



4th .80S 



)> J."-"- if ,, 



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, MiJcania, Phaseolus, &c. The 
Seyphanthus made one revolution in 1 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. 57 m. 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. 



Chap. I. 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 Ijiomoea 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 Leguminosre, and we 
have in the table another in the Acanthaceae. I have 
seen no instance of two species of the same genus 
twining in opposite directions, and such cases must be 
rare ; but Fritz Miiller * states that although Mihania 



* Journal of the Linn. Soc. interesting paper, in which he 
^Bot.) vol. ix. p. 314. I shall corrects or confirms various state- 
have occasion often to quote this ments made by me. 



34 TWINING PLANTS. Chap. L 

8candens 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 Solarium 
dulcamara (Dutrochet, torn. xix. p. 299), revolve and 
twine in two directions : this plant, however, is a most 
feeble twiner. Loasa aurantiaca (Leon, 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 d'appui 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 Scyplianthus 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 Loasa Herhertii, and six in ascending a support. 



Chap. I. 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 
jueunda ; 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. I 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 
& 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. Chat-. 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 Solarium 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 perichjmenum), which I have 
observed twining up a young beech-tree nearly 4J 
inches in diameter. Mohl (p. 134) found that the 
Phaseohis multiflorus and Ipomoea purpurea could not, 



* In another genus, namely left ; and I once 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 

Muller says (ibid. p. 349) tliat the same manner as so frequently 

" the stem twines indifferently occurs with Loasa." 
from left to right, or from right to 



Chap. 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 I hear from 
Dr. Hooker that at Kew the Buscus androgynus has 
ascended a column 9 inches in diameter ; and although 
a Wistaria 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 parviftora, one of the Menispermacese, and 
with some Dalbergias and other Leguniinosae.* 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 Miilkr states (ibid. p. ispermacese. He adds in his 
349) that he saw on one occasion in letter to me that most of the 
the forests of South Brazil a 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. Chap. I. 

thev 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 Ceropepia Gardnerii 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 Sjrfiterostemma 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 Lygodium articulaium 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. 
seandens made five revolutions, each at the average 
rate of 5 hrs. 45 m. ; and this represents fairly well the 
usual rate, taking quick and slow movers, amongst 



Chaf. I. 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 them selves, 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. Chai\ 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 (torn. xvii. pp. 994, 996) has given such 
precise observations on this head with respect to the 
common pea that I 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 Ipomoea jucunda 
made a complete circle in 5 hrs. 30 m. ; the semi- 
circle from the light taking 4 hrs. 30 m., and that 
towards the light only 1 hr. Lonicera hrachyjpoda 
revolved, in a reversed direction to the Ipomoea, in 
8 hrs. ; the semicircle from the light taking 5 hrs. 23 m., 
and that to the light only 2 hrs. 37 m. Prom 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. 



Chap. I. 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 
T.amus 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. purjmreum 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 Grseca 
(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 Asclepiadaceae are twiners ; 






42 TWINING PLANTS. Chap. I. 

but Azclepias nigra only " in fertiliori solo incipit 
scanclere 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 
bear 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 ConvolvulaceaB 
are excellent twiners ; but in South Africa Ipomcea 
argijrdeoides 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 sj)ecies 
of Phaseolus are twiners ; but certain varieties of the 
P. multijlorus produce (Leon, p. 681) two kinds of 
shoots, some upright and thick, and others thin and 
twining. I have seen striking instances of this curious 



Chap. I. TWINING PLANTS. 43 

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

Solatium 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 
(torn. 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 Soya camosa revolve 



44 TWINING PLANTS. Chap. 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 



Chap. H. LEAF-CLIMBERS. 45 



CHAPTEK II. 

Leaf-Climbers. 

Plants which climb hy the aid of spontaneously revolving and sensitive 
petioles Clematis Tropxolum Maurandia, flower-peduncles 
moving spontaneously and sensitive to a touch Rhodochiton 
Loplwspermum internodes sensitive Solatium, thickening of 
the clasped petioles Fumaria Adlumia Plants which climb hy 
the aid of their produced midribs Gloriosa Flagellar ia 
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 Tropseolum were 



6 LEAF-CLIMBEES. Chap. II. 

observed, in order to see what amount of difference 
in the manner of climbing existed within the same 
genus ; and the differences are considerable. 

Clematis. 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 vounor leaf 
be rubbed wdth 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 
geemed 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 
caught hold of two thin branches. A forked twig placed 
so as to press lightly on the under side of a young 



Chap. 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-CUMBERS. Chap. 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 
5 hrs. 10 m. 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 



Chap. II. 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. A shoot made three revolutions 
against the sun at an average rate of 3 hrs. 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. 12 m. Thev 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 tw r o 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, thai 
the petioles at first seem ill-adapted for clasping. 



50 LEAF-CLIMBERS. Chap. IL 

Nevertheless, the main service of the revolving move- 
ment is to brins; 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 
2 hrs. 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 24 hrs. 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 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 



Chap. II. 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 mierophylla, var. leptophyUa. 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. Chap. II, 

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 curved 
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. 35 m. 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 objects. 
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. viticdla, 
G. fiammula, and C. vitalba move spontaneously ; and, 
judging from C. Sieboldi, this probably is the case with 



Chap. II. CLEMATIS. 53 

G. montana and G cahjcina. I ascertained that the 
simple leaves of G. 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 
2 hrs. 40 m. 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 4 J 
inches, and that by the apex of the penultimate inter- 
node only 1J 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. Each bears three pairs 
of lateral leaflets and a terminal one, all supported on 



54 



LEAF-CLIMBERS. 



Chap. II. 



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 remain ler ; it will, however, clasp a stick 



Chap. II. CLEMATIS. 55 

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 nig.) 
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 45 m., and in 
1 hr. 10 m. moved through ninety degrees ; whilst 
a lateral sub-petiole did not become sensibly curved 
until 3 hrs. 30 m. 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 G. 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 G. 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. Chap. II. 

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. 
45 m. 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 If, and in another case If 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 1st 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 



Chap. II. CLEMATIS. 07 

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 3 hrs. 15 m. In another 
case a petiole curled completely round a stick in 
12 hrs. These petioles were left curled for 21 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 12 hrs. and 14 hrs. Lastly, a 



58 LEAF-CLIMBERS. Chap. II. 

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 
looj} of fine string, weighing 1*04 gr. (674 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 (8*01 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 



Chap. II. 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 
I 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 
l - 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 anode 
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 man\ 



60 LEAF-CLIMBERS. Chap. II. 

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 G. 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. 

Trop^eolum. I observed T. tricolorum, T. azureum, 
T. pentaphyllum, T. peregrinum, T. elegans, T. tuberosum, 
and a dwarf variety of, as I believe, T. minus. 

Tropseolum tricolorum, var. grandiflorum. The 
flexible shoots, which first rise from the tubers, are 



Cuap. II. TROP^OLUM. 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 
leaves 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. Chap. II. 

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. 

Trojyseolum azureum. An upper internode made four 
revolutions, following the sun, at an average rate of 
1 hr. 47 m. 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 



Chap. II. TROP^OLUM. 63 

to move perceptibly in 5m, and another in 6 ra. 
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 Jth of a grain caused another 
petiole to curve. 

Tropaeolum pentaphyUum. This 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- 
paeolum 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 20 m., and others in from 8 m. 
to 10 m. Their curvature usually increased greatly in 
from 15 m. to 20 m., and they became straight again in 
between 5 hrs. and 6 hrs., but on one occasion in 3 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 anode 
between the stem and petiole is sensitive. 



64 LEAF-CLIMBERS. Chap. II 

Tropseolum i^eregrinum. The first-formed internode3 
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. 48 niin. 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. 47 m., 1 hr. 46 m., 
and 1 hr. 48 m. The present species cannot twine 
spirally, which seems mainly due to the rigidity 
of the stem. In a 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. 

Tropseolum 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 17m.; and 



Chap. II. TROP^EOLUM. 66 

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

Tropteolum 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 bo 
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. 

Tropseolum minus (?). The internodes of a variety 

named " dwarf crimson Nasturtium " did not revolve, 

4 



66 LEAF-CLIMBERS. Chap. II. 

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. tricolorum, 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 T. 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. 

Antirrhine^. In this tribe (Lindley) of the 
ScrophulariaceaB, at least four of the seven included 
genera have leaf-climbing species. 

Maurandia Barclayana. 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 spirally, but climb excellently by the aid cf 



Chap. H. MAUKANDIA. 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 ^th of a grain caused them to 
bend. 

Maurandia semper jl or ens. 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. I 
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. Chap. IL 

which alone has the power of revolving ; so that they 
conld 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 1J 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 anv 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 (1J 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 of a large number 1873, p. 34. 
of plants are irritable, and bend 



Chap. II. MAUEANDIA. 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 } r oung as to be only 
three-tenths of an inch in length, became curved when 
rubbed. On the other hand, peduncles above 1J 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 
Scrophulariaceae had possessed tendrils produced by 
the modification of flower-peduncles, I should have 
thought that this species of Mauranclia 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. Chap. II. 

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 Yitis or 
Cardiospermum. ^ 

BJwdochiton 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. 10 m. 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 nig.), 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 



Chap. H. 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 ccandens, var. purpureum. Some 
long, moderately thin internodes made four revolu- 
tions at an average rate of 3 hrs. 15 m. 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 revolving 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, 
euta, which, according to H. de 



72 LEAF-CLIMBERS. Chap. II. 

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 
cirrlwsa and, to a limited degree, those of L. elatine 
have the power of clasping a support. 

$olanace.e. Solatium 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. 26 m. 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 2J 
grains (163 mg.) ; but in the hothouse one was made 
to curve by a loop weighing T64 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 



Chap. II. 



SOLAN CM. 



73 



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. S. 
Solanuvijatmi'noidet, with one of its petioles clasping a stick. 

slow that the act required several w r eeks ; 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 



74 LEAF-CLIMBERS. Chap. II. 

can hardly be removed from its support. On com- 
paring a thin 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. 
Solarium jasmivoides. 

A. Section of a petiole in its ordinary state. 

B. Section of a petiole some weeks alter 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 become much less prominent, and the twe 
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 



Chap. II. 



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.* 

Fumamace^e. Famaria 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 Masters informs 
me that in almost all petioles 
which are cylindrical, such as 
those bearing peltatu leaves, the 
woody vessels form a closed rlns; ; 
semilunar binds of ves-s Is being 
confined to petioles which are 
channelled along their upper 



surfaces. In accordance with this 
statement, it may be observed 
that the enlarged and clasped 
petiole of the Solamim, with its 
closed ring of woody vessels, lias 
become more cylindrical than it 
was in its original unclasped 
condition. 



76 LEAF-CLIMBEKS. Chap. II. 

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 1 hr. 15 m., 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 elaj)sed, 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 



Chap. U. 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 1 hr. 36 m. a narrow ellipse, open at one end, and 
exactly three inches in length ; a second ellipse was 
broader, more irregular, and shorter, viz., only 2^ 
inches in length, and was completed in 2hrs. 2 m. 
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, Bignonia 
unguis and its close allies, though aided by tendrils, 
have clasping petioles. According to Mohl (p. 40), 
Cocculus Japonicus (one of the Menispermacea3) and a 
fern, the Ophioglossum 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. Chap. II. 

LiLiACEiE. Gloriosa PlantiL The stem of a half- 
growri 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 
4 hrs. 35 m. 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 
3 hrs. 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 



Chap. II. GLOKIOSA. 79 

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 is 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. 

CommelynacezE. 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. Chap. H. 

the stein revolve. Hence this plant acquires its 
climbing powers later in life than does the Gloriosa 
lily. According to Mohl (p. 41), Uvularia (Melan- 
thaceae) 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. Isevis 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 JV. leevis 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 



Chaf. II. LEAF-CLIMBERS. 81 

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-climhers. 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. Chap. II 

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 a 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 JjOflxospermum 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 interncdes, and are thus better adapted to 



Chap. II. LEAF-CLIMBEKS. 83 

seize distant objects. The petioles of the perfect 
leaves of Tropseolum 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 revolving movement of the internodes 
superfluous; and this latter power has consequently 
become much enfeebled. In certain species of Tro- 
pseolum, 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. 

Tendril-Beakers. 

Nature of tendrils Bigxoniace^:, 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 Polemoxiace^e 
Cobxa scandens, much branched and hooked tendrils, their manner 
of action Legitminos^: Composite Smilace^e Smilax asjyera, 
its inefficient tendrils Fumariaceje 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 nsed 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 Midler has described 
(Journal of Linn. Soc. vol. is. p. 
344) many striking cases in 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 : 



(1.) 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 
Uelinus. (4.) Tlants with the r 
branches much modified and 
temporarily converted into ten- 
drils, but which may be again 



Ciiap. m. 



TENDKIL-BEARERS. 



85 



Mfthl, 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 : Bignoniacete, Polemoniacex, Legu- 
minosse, Comjwsitas, Smilaceee, Fumariacess, Cucurhitacese, 
Vitacess, Sapindaeese, Passifloracete* 



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 Mohl 
observed about the same time the 



singular phenomenon 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 nc ces- 
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 tendril* 
of certain Cucurbitaceous plants. 



86 



TENDRIL-BEABEKS, 



Chap. III. 



Bignoniace^}. 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. 

Bignonia. 

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 



Chap. ILL BIGNONIACE,E. 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-BEAREKS. Chap. III. 

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 



Chap. HI. BIGNONIACE^. 89 

which I have observed ; and it probably could ascend 
a polished stem incessantly tossed by heavy storms. 
To show how important 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. 33 m. 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 aerial 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 



90 TENDRIL-BEARERS. Chap. III. 

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. unguis and 
B. Tweedyana. The young internodes sweep large 
circles, one being completed in 2 hrs. 15 m., and 



Chap. HI. BIGNONIACE^. 91 

a second in 2 hrs. oo m. 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. Chap. 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 np 
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 7 m. 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 become irritable. 
The irritability spreads but little from one part when 



Chap. IIL BIGNONIACE^l. 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 TENBKIL-BEARERS. Chap. HI. 

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

Bignonia tequinoctialis, var. Cliamberlaynii. 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 following 
species with undivided tendrils : 

Bignonia speciosa. The young shoots revolve 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 



Chap. in. BIGNONIACE^I. 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, Passifloraceous, 
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-BE AEERS. Chap. III. 

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. 
capreolata 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 pida. This species closely resembles the 



Chap. IIL BIGNONIACE^. 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 2J 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 ^th of a grain produced 
no effect. On two occasions the terminal branches 
became slightly curved in 10 m. after they had touched 
a stick ; and in 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 TENDKIL-BEAKERS. Chap. IIL 

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 



Chap. III. BIGNONIACE^. 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 zinc 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 TENDEIL-BEAEEES. Chap. III. 

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 
a few more days the hooks were converted into whitish, 
irregular balls, rather above the 20-th of an inch (1*27 
mm.) in diameter, formed of coarse cellular tissue. 



Chap. III. BIGNONIACExE. 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 craw] 



102 TENDRIL-BEARERS. Chap. 1IL 

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

I infer from the adherence of the fibres to the discs 
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 Poli/podium 
incanum abounds on the forest-trees in the districts of 



* Fiitz Midler states (ibid. p. object, terminate in smooth shining 

348) that m South Brazil the discs. These, however, after ad- 

trilid tendrils of Haplolophium, hering to any object, sometimes 

(one of the Bignoniacese) without become considerably enlarged, 
having come into contact with any 



Chap. III. BIGNONIACE^. 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 scaler {Bignoniaceee). 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. 13 m. 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 recommenced revolving. Such strongly 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. Chap. Ill 

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 o23posite 
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 E. miniatus 
more plainly than in E. scaler. The tendrils in this 
genus act in some respects like those of Bignonia 



Chap. III. BIGNONIACE^J. 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, 



106 TENDRIL-BEARERS. Chap. III. 

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. 

Polemoniace M. Cdbcea 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. 
15m.; 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 



Chai>. DDL POLEMONIACE.E. 107 

the internocles revolve ; so that here we have the tendril 
alone moving. On the other hand, with most of the 
species of Bignonia and the Eccremocarpus, the inter- 
nodes, tendrils, and petioles all revolved. The long, 
straight, tapering main stem of the tendril of the Cobee.a 
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 minnte 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 



108 TENDRIL-BE AEERS. Chap. III. 

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 climbino:- 
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 sj)ace 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 
ail power of movement, and contracts spirally into an 
entangled mass. Although the tendrils revolve with 
unusual rapidity, the movement lasts for only a short 



Chap. IH. POLEMONIACE.E. 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 TENDEIL-BEAEEKS. Chap. III. 

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 Cobeea 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. It might have been thought 
that a tendril, thus hooked by the extremity of a single 
branch, could not have fairly grasped its support. 



Chap. III. POLEMONIACE^. Ill 

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. 

Leguhinosjl Pisum sativum. The common pea 
was the subject of a valuable memoir by Dutrochet,* 
who discovered that the internodes and tendrils 



* Comptes Kendus, torn. xvii. 1848, p. 989. 



112 TENDRIL-BEAKERS. Chap. Ill 

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 
p.m. 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 scale. Dutrochet 



Chap. III. 



LEGUMINOS^}. 



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 the upper internode of the common Pea, traced on 
a hemispherical glass, and transferred to paper; reduced one-half in size. (Aug. 1st.) 



No. 

1 . 

2 . 

3 . 

4 . 

5 . 

6 . 

7 . 

8 . 



H. M. 

16 



37 
7 

30 


30 



10 
11 
11 
12 
12 
1 
1 





No. 




A.M. 


9 . . . 





10 . 







11 . 







12 . 




P.M. 


13 . 




j 


14 . 




i 


15 . 




n 







M. 

55 
25 


30 
48 
40 

5 





No. 


P.M. 


16 . . . 


N 


17 . . . 


m 


18 . . . 





19 . . . 


n 


20 . . . 


m 


21 . . . 


n 


22 . . . 



H. M. 
5 25 

5 50 

6 25 



P.M. 





45 



8 30 

9 15 



spontaneously revolve, as well as the young inter- 
nodes and tendrils; but he does not say that he 
6 



114 TENDRIL-BEAKERS. Chap. III. 

secured the intern odes ; 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 



Chap. III. LEGUMINOS^. 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, 
except 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 



116 TENDRIL-BEAEERS. Chap. III. 

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. 

Lathy r us grandijiorus. 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. 

Composite. Mutisia clematis. The immense 
family of the Coraposita: is well known to include 
very few climbing plants. We have seen in the Table 
in the first chapter that Milcania scandens is a re- 
gular twiner, and F. Miiller informs me that in & 



Chap. III. COMPOSITE. 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 TENDEIL-BEARERS. Chap. III. 

night and rises during the day, moving, also, during 
the day in 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. 

Smilace^e. 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 1J to If inches in length, are 
thin, and have slightly curved, pointed extremities. 
They diverge a little from each other, and stand at 
fiist nearly upright. When lightly rubbed on either 



* < 



Lemons de Botanique,' &c, 1841, p. 170. 



Chap. in. 



SMILACE^J. 



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 




Pig. 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 TENDRIL-BEARERS. Chap. III. 

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 



Chap. III. FUMARIACE^. 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. 

FuMAMACEiE. 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 tendrils, for they are completely 
destitute of laminae or blades. Consequently, we here 
behold a plant 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 



122 TENDEIL-BEAEEES. Chap. HI. 

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, 
*nd 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 1J inch in 
length (above the leaflet /), 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 (2*116 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, c, d) are highly 
sensitive, for a loop of thread weighing only the one- 
sixteenth of a grain (4*05 mg.) caused them to become 



Chap. III. 



FUMARIACE.E. 



123 



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




Fig. 8. 
Oorydalis 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 TENDKIL-BEAKERS. Chap. III. 

petioles (/ to I) doing 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 Mold'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 thalidrifolia. In this allied plant the 



Chai\ III. FUMAR1ACE.E. 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-BEAKERS. Chap. III. 

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 Bignoniacese and Cobaea. 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 Corydcdis claviculata. But in all cases the 
petiole after a time is angularly and abruptly bent 
downwards like that of Eccremocarpus. 



Chap. IV. CUCURBITACE.E. 127 



CHAPTEK IV. 

Tendril-Bearers (continued). 

CuCurbitace^: Homologous nature jf 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 ViTAC-as 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 Sapindace^e Passifloraceje Passiflora gracilis Rapid 
revolving 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. 

CucurbitacezE. 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 



* I am indebted to Prof. Oliver f ' Gardeners' Chronicle,' 1864, 

for information on this head. In p. 721. From the affinity of the 

the Bulletin de la Societe Bota- Cucurbitacese to the Passifloracese, 

nique de France, 1857, there are it might be argued that the 

numerous discussions on the tendrils of the former are modified 

nature of the tendrils in this flower-peduncles, as is certainly 

family. the case with those of Passion- 



L28 TENDRIL-BEARERS. Chap. 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 
bv 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, a few years ago in my own tendril." 



Chap. IV. CUCUKBITACE^I. 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 on revolving. 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 



J 30 TENDRIL-BEARERS. Chap. IT. 

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 
fts 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 rejDeatedly 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 



Chap. IV. CUCURBIT ACE M. 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, 
seen 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-BEAREKS. Chap. 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 measurements I proved that 



Chap. IV. CUCURBIT ACEM. 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 



134 TENDKIL-BEAEERS. Chap. 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 Echinocyatis. 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 
Echmocystis, 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 HanburyG, 
the inwardly directed, spur-like branch, from being 



Chap. 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 davs, 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 Bignonict and of Ampelopsis ; but 
in the Hanburya the layer is developed along the 
terminal * inner surface, sometimes for a length of 
If 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 ; 
or 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. 



\oQ TENDRIL-BEAKERS. Chap. 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 soon 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 Warscewiczii, 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 Hanbunja ; 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. 

Vitace^e. In this family and in the two following, 
namely, the Sapindacese and Passinoracese, 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 Cucurbitaceae. The homological nature, 
however, of a tendril seems to make no difference 
in its action. 



Chap. IV. 



VITACILE. 



137 



Viiis 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. 

B. 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. Chap. IV. 

taneously from side to side ; and on a very hot day 
one made two elliptical revolutions, at an average rate 
of 2 hrs. 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 unusually 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. 



Chap. 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. 

B. Flower-tendril, with a scale at its base. 



C. Sub-Peduncle, bearing the flower-buds. 

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 TENDEIL-BEARERS. Chap. 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 onl} 



Chap. IV. VITACE^E. 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 8J 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 TENDKIL-BEAREES. Chap. 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 flower- 
stalks closely resemble in structure those borne by 
Cissus. This genus, belonging to the same family of 
the Vitacese, produces well-developed tendrils and 
ordinary bunches of flowers ; but there are no gradations 
between the two states. If the 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 



Chap. IV. VITACE^J. 143 

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 tor 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 J 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 30 or 40 m. Half this weight pro- 
duced no effect. The long foot-stalk is much less 



144 TENDEIL-BEAREKS. Chap. 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 aniarcticus. 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. 

Ampelojpsis 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 



Chap. IV- VITACE^J. 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 hat 
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. 



146 



TENDKIL-BEAREUS. 



Chap. IV 



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 cajpreolata. 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. 
Tot. Soc. Edinburgh, vol xi. p. 
2!)2) that the tendrils of Amp. 
Veil chit bear small globubr discs 
before ihey 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 



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



CHAr. IV. VITACEJS. 147 

tip ; this was also observed (p. 71) by Mohl. 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. 



Chap. IV, 



week or two shrinks into the finest thread, withers and 





Fig. 11. 
Ampdopsis 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 branches 
thicsened 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 thns becomes highly elastic, so 



Chap. IV. VITACE^. 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 ! 

SAriNDACE^:. Cardiospermum halicacalum. In this 



150 TENDBIL-BEARERS. Chap. 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 4J inches in 
length. Near the summit, above two little bracts, it 
divides into three branches. The middle one divides 




Fig. 12. 

Cardiospermum halicacdbum. 

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. 



Chap. IV. SAPINDACE.E. 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 3 hrs. 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 3 hrs. 47 m. The average rate of these six 
revolutions was 1 hr. 46 m. The stem shows no 
tendency to twine spirally round a support ; but the 
allied tendril-bearing genus Paullinia 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. 
I hooked a tendril on to a twig ; and in 1 hr. 45 m. it 
was curved considerably inwards ; in 2 hrs. 30 m. 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-BEAKERS. Chap. 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 clasj>s 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. 

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



* Fritz Miiller 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 has clasped 

bearing only a single tendril ; and the plant's own stem. 



Chap, IV. PAS3IFL0RACEJL 153 

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 Vitis. 

Passiflorace^e. 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 E. Darwin, made sketches for me of their 
earliest state of development in the hybrid P.Jloribunda. 
The two organs appear at first as a single papilla which 
gradually divides ; so that the tendril appears to be a 
modified branch of the flower-peduncle. My son 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 internocles 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. 4 m.; 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. Chap. IV. 

1 hr. 1 hi. 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 
g^nd 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 Fahr.) in the following times r 

revolve even at a quicker rate 40 m., 45 m., 38 m., and 46 m. 

than those of P. gracilis ; four One half-revolution was per- 

revolutions were completed (the formed in 1 5 m. 



Chap. IV. PASSIFLORACE^E. 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. Chap. IV. 

I repeated the experiment made on the Ecliinocystis, 
and placed several plants of this Passiflora so close 
together, that their tendrils were rej)eatedly 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 ^ud 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 -j^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 3 hrs. 5 m., 2 hrs. 40 m., 
and 2 hrs. 50 m. ; perhaps it might have travelled more 



Chap. IV. PASSIFLOKACEiE. 157 

quickly when nearly full-grown. A plant was placed 
in front of a window, and, as with twining sterns, 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 j^th of a grain 
(4*625 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 10 m. 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 TENDKIL-BEARERS. Chap. 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. 22 m. ; 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. 7 m. 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 Vitacese, SapindaceaB and Passi- 
floraceae, 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 
Polygonaceae. In two or three species of Modecca, one 
of the Papayaceas, 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 



Chap. IV. SPIKAL 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 Tropseolum tricolor um. 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 Yine, Passiflora, Bryony, the basal portion never 
forms a spire. 

I have 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. Chap. 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 



Chap. 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 Echinocijstis 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 Echinocijstis 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 davs after 
all revolving movement has ceased. A full-grown 
tendril of Passiflora quadrangular is 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. Chap. 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 Ampelojms 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 extremitv, 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 



Chap. 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 Yitaceae, which are modified flower- 
peduncles. But in the 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 Cobaea 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 TENDEIL-BEAEEES. Chap. 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 skip with two anchors 
down, and with a long range of cable ahead to serve 
as a spring as she surges to the storm. 

When an 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 suj>port 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 ojypositely turned spires being 
separated by a short straight portion. This curious 



Chap. IY. 



SPIRAL CONTRACTION. 



165 



and symmetrical structure lias 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 
torn 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 Bryonia dioica, 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. Loon in Bull. 
Soc. Bot. de France, torn. v. 1858, 
p. 6>-0. Dr. H. de Vries points 
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 
6upport, it begins in some days to 



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



L66 TENDKIL-BEAKEKS. Chap. IV 

in opposite directions, with straight pieces between 
them; and M. Leon 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. 
If 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 



Chap. IV. SPIRAL CONTRACTION. 167 

their own axes, at tlie 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 
Ecliinocystis and Passiflora quadrangular is ; and as 
the tendril contracted itself into successive spires, the 
vane 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-BE AKEKS. Chap. 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 oj)posite to those, whether turned 
to the right or to the left, which are first made. Take 
a j)iece 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 thev take several consecutive turns in 
one direction and then the same number in an opposite 



Chap. 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 
sj)ecies have the power of revolving. The Yine is 
the weakest revolver observed by me, apparently 
exhibiting only a trace of a former power. In the 
Eccremocarpus 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 oiBignonia littoralis 
move much slower than the internodes. Generally, 



170 TENDRIL-BEARERS. Chap. IV. 

the internod.es and tendrils revolve together at the 
same rate ; in Cissus, Cobaea, and most Passiflorse, 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 grandijlorus 
and Ampelopsis. In most Bignonias, Eccremocarpus, 
Mutisia, and the Furnariacese, 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 oi 
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 



Chap. 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 object, and curve towards the touched 
side. With several plants a single touch, so slight as 
only just to move the highly flexible tendril, is enough 
to induce curvature. Passiflora gracilis possesses the 
most sensitive tendrils which I have observed : a bit 
of platina wire ^-th 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 ^nd of a grain (2*02 mg.) With the 
tendrils of several other plants, loops weighing ^th of 



172 TENDRIL-BEARERS. Chap. IV. 

a grain (4'05 mg.) sufficed. The point of a tendril of 
Passifiora 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 Passifiora gracilis and 
of the Ecliinocystis. 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 Coba3a 
(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 



Chap. IV. SDMMAEY. 173 

by a 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 Hanhurya 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 TENDEIL-BEAKERS. Chap. IV. 

with a stick, do they not, like twining plants, spirally 
wind ronnd 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 
sj)ontaneously bends more than any other part; and 
this is of high importance for the ascent of the plant, 
as may be seen on a windy day. It is, however, possible 
that the slow movement of the basal and stifTer 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 
Cobasa 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 



Chap. 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. 
Foi instance, the tendrils of Bignonia capreolata bend 
from the light to the dark as truly as a wind- vane from 
the wind. In the 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 tb^ker, and sometimes more durable to a 
wonderful degree; and this shows how much their 
internal tissues must be changed. Occasionally it is 



176 TENDRIL-BEAKERS. Chap. IV. 

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 scqui- 
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 fall 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 o{ 

of Botany,' Eng. Translation, ]S75, different thicknesses. He further 

p. 280), has 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. 



Chap. 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. unguis the petioles 
are more sensitive, and have greater power of raove- 
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 aerial 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. littoralis 
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, 



178 TENDRIL-BEAKERS. Chaf. 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 Cobrea 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. 



Chap. IV. SUMMAEY. 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 
Pejjonopsis adhserens. 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 HayAolopliium 
and of one species of Ampelopsis,) on the stimulus from 
contact. It is a singular fact that three families, so 
widely distinct as the Bignoniacea?, Yitacese, and 
Cucurbitaceae, 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. It is rash to differ from so great 
an authority, but I cannot believe that one at least of 



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



180 



TENDKIL-BEAKEKS. 



Chap. 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 to a 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. 132) twice or thrice round 



* It occurred to me that the 
movement of nutation and that 
from a touch might be differently 
affected by anaesthetics, in the 
same manner as Paul Bert has 
shown to be the case with the 
Bleep-movements of Mimosa and 
those from a touch. I tried the 
common pea and Fassiflora gra~ 



cilis, but I succeeded only in ob- 
serving that both movements were 
unaffected by exposure for 1 hrs. 
to a rather large dose of sulphu- 
ric ether. ~In this respect they 
present a wonderful contrast with 
Drosera, owing no doubt to the 
presence of absorbent glands in 
the latter plant. 



Chap. IT. 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 TENDKIL-BEAKERS. Chap. 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. 



Chap.V. 



HOOK-CLIMBEES. 



183 



CHAPTER Y. 

Hook ane Root-Climbers. Concluding Remarks. 

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

Hook-Climbers. In niy 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 Muller 
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 liffht. 
The few hook-climbers which I have observed, namely, 
Galium 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. 10G) that it is highly 
characteristic of climbing plants to 
produce thin, elongated, and flexi- 
ble stems. He further remarks that 



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



184: 



HOOK-CLIMBERS. 



Chap. 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 Galium ; some other twiners have stiff 
reflexed hairs ; and Dijpla&enia 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. 
18t>5, p. 282) of the present work. 
He has observed that the strong 
summer shoots of the Michigan 
rose {Rosa seligero) are strongly 



disposed to push into dark crevice s 
and u way 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 
tough t the light. 



CilAP. V. ROOT-CLIMBERS. 185 

Boot-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 Marcgravia dubia in my hothouse. 
Boot-climbers, as far as I have seen, namely, the Ivy 
(Hedera helix), Ficus rejiens, and F. barbatus, have no 
power of movement, not even from the light to the dark. 
As previously stated, the Hoya carnosa (Asclepiadacese) 
is a spiral twiner, and likewise adheres by rootlets 
even to a fiat wall. The tendril-bearing Bignonia 
Tweedyana emits roots, which curve half round and 
adhere to thin sticks. The Tecoma radicans (Big- 
noniacese), 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. 

I 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 EOOT-CLIMBEES. Chap. 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 



Chap. V. ROOT-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 Fie us 
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 rejpens 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. Spill rr has recently shown a fine state of division to the air, 

(Chemical Society, Feb. 16, 1865), giadually becomes converted into 

in a paper on the oxidation of hi ittle, resinous matter, very similar 

india-rubber or caoutchouc, that to ^hell-lac. 
this eubbtance, wlien exposed in 



188 



ROOT-CLIMBERS. 



Chap. 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 aromaiica emits aerial 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 net 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 Muller informs me 
that he saw in the forests of 
Suuth Brazil numerous 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 steins 
of twining plants which were thus 
ascending the trees; but he after- 
wards found that they were the 



aerial 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 plants. 
The aerial roots of some other 
species of Philodendron hang 
vertically downwards, sometimes 
for a length of more than fifty feet 



Chap. 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. Koot-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 EEMAEKS. Chap. 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 w r ell, 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 w r ould 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- 
climbers were in most cases at first twiners, and subse- 



Chap. 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 priniordially 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 Cucurbitaceae, Passi- 
floracese, and Vitaceae. 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 halsamina, 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 Yine 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- 



1 92 CONCLUDING REMARKS. Chap. 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 Tropaaolum, 
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- 



Chap. V. CONCLUDING REMARKS. 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 kidnev-bean, which 
had ascended exactly two feet in height, and it w r as 
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. Chap. 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 snch 
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 adjoining 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 laminae 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 laniinse are still occasionally 
retained. In four genera of the Fumariaceae we can 



Chap. V. CONCLUDING EEMAKKS. 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 
Dicsntra, we should almost certainly see a series like 
that now exhibited by the above-named three genera. 
In Tropseolum tricolorum we have another kind of 
passage ; for the leaves which are first formed on the 
young stems are entirely destitute of lamina?, and 
must be called tendrils, whilst the later formed leaves 
have well-developed lamina?. 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 laminae 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 Antirrhineae, of Solanum, Cocculus, and 
Gloriosa, have within the same family and even within 
the same genus, relatives which are twiners. In the 



196 CONCLUDING KEMAKKS. Chap. 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 Fumariacese 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 Muller. 
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 of the branches of the Lophospermum 
were to abort, these branches would be converted 
into true tendrils. Nor is there anything improbable 



Chap. V. CONCLUDING KEMAEKS. 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 



* Quoted by Cohn, in his handl. der Schlesischen Gesell. 
remarkable memoir, " Contractile 1861, Heft i. s. 35. 
Gewebe im Pflanzenreiche," ' Ab- 



198 



CONCLUDING REMARKS. 



Chap V. 



common 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,ihe 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 Cardiosj)ermum), 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 
movements, I now find, have heen 
for some time known to occur, 
for instance with the flower-stems 
Df Brassica naptcs and with the 
leaves of many plants : Sachs' 
Text-Book of ltotany' 1875, pp. 
7G6, 785. Fritz Muller also has 



shown in relation toonr present sub- 
ject ('Jenaischen Zeitschrift/ Bd. 
V. Heft 2, p. 133) that the stems, 
whilst young, of an Alisma find 
of a Linum are continually 
performing slight movements to 
all points of the compass, like 
those of climbing plants. 



Chap. 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 agaiu. 
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. 37 et seq.) with foliar and axial organs of plants. 



200 CONCLUDING REMARKS. Chap. 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 Yine, we see no 
loss in the power of climbing, but only a remnant of the 
revolving 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 Bignoniacese, 
we see a last and doubtful trace of the power of 
revolving. 

With respect to the abortion of tendrils, certain 
cultivated varieties of Cucurhita pejpo 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 sj)ecies 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. torn. vi. 1856, p. 31. 



Ciiap. 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. nissolia 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. aphaea 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 L. 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 KEMAEKS. Chap. 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. a'pliaca), 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 aerial roots all possess this power. 

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



* Moquin-Tandon (Elements de this nature was suddenly effected ; 

Teratologic, 1841, p. 15G) 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. 



Chap. V. CONCLUDING REMAKES. 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. If a 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 movement is often accelerated or retarded 



204. CONCLUDING REMARKS. Chap. 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 spontaneous 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. If they 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. 



Chap. V. CONCLUDING EEMARKS. 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, Cobwa, 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- 
cluded. 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 cf 
the largest, well-defined orders, such as the Composite, 
ftubiaceae, Scrophulariaceoe, Liliacea?, &c, 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 EEMAKKS. Chap. 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, 200 

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 dioica, 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 twiDing in South Africa, 42 

Cissus discolor, 143 

Clematis, various species of, leaf- 
climbers, 46 

Coba>a scandens, 106 

Combretum, 41 

Corydalis claviculata, 121 

Cucurbitaceae, nature of tendrils, 127 

Cucurbita pepo, aborted tendrils, 200 

Cuscuta, stems of, irritable, 17, 71 

Diceutra 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 

Kchinocystis lobata, 128 

Ferns, twining, 38 

Ficus repens, a root-climber, 185 

Fiagellaria 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 
developmsnt of perfect tendrils, 195, 
196 



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

on tendrils of Passiflora, 154 

Sicyos, 172 



on Rosa setigera, 1 84 



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 

Ipomcea argyraeoides, 42 

Ivy, 185, 188 [183, 199 

Jaeger, Prof. G., on climbing plants, 

Kerner, on the irritability of flower- 
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 

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

, on spiral contraction of teu- 
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 



INDEX. 



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 ab( rtion of the 

leaves of the bean, 202 
Miiller, Fritz, on the structure of the 

wood of climbing plants, 44 
on plants scrambling over 

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, 80 

Nutation, revolving, 11 

Ophioglossum Japonicum, 77 

Palm, reference to work of, 1 

Passiflora acerifolia, 154 

gracilis, 153 

punctata, 156 

quadrangularis, 157 

Paulliuia, 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 



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 
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 knowledgcof, 85 

, spiral contraction of, 158 

, summary on, 169, 202 [180 

, 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 
Tropaeolum, 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 mc 



ements of ten- 



drils, 180 
Vitis vinifera, 137 
Zanonia Indica, 136 



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