1876.] 
Notices of Books . 
105 
this group, which includes the vine, the pea, and a number of 
Bignonias, the climbing organisation reaches its highest de- 
velopment. The twiner, in ascending a tree by its spiral folds, 
must, in order to reach the light above, describe a line very much 
longer than the perpendicular height to which it rises. Con- 
sequently it is compelled to expend a relatively large amount of 
matter. But the tendril-climber can ascend nearly in a straight 
line. The adbion of the tendrils is very curious. They revolve, 
and the shoot of the plant not unfrequently revolves also. If 
they touch any objedl they immediately begin to coil round it 
if thin enough, and become at the same time very much thicker 
and stronger. Tendrils which do not succeed in clasping any- 
thing generally wither and fall off. If the object found is too 
thick to be clasped, the points of the tendrils in some plants 
“ exhibit a singular habit, which in an animal would be called an 
instindb.” They continually search for any little chink or hole 
into which they may insert themselves. In other cases the ends 
of the tendrils are converted into flat discs, which are pressed 
close to the surface up which the plant is climbing. Bignonia 
Tweedy ana, which Mr. Darwin has carefully studied, “ combines 
four different methods of climbing generally characteristic of 
different plants, namely, twining, leaf-climbing, tendril-climbing, 
and root-climbing.” 
Among true root-climbers we flne a curious phenomenon — 
Ficus repens — a plant which creeps up a wall exadtly like ivy, 
secretes from its rootlets an adhesive fluid, by which they are 
cemented to the wall or rock. This fluid w T as found to be slightly 
viscid, and on exposure to the air did not dry up. From experi- 
ments and observation made it would appear that the rootlets 
“ first secrete a slightly viscid fluid, subsequently absorb the 
watery parts, and ultimately leave a cement.” This appears to 
be a modified form of caoutchouc — a substance in which the genus 
Ficus is well known to abound. 
A careful consideration of climbing plants can scarcely, in our 
opinion, fail to furnish evidence in favour of the dodbrine of 
evolution. If we place any plant in the open ground, freely 
exposed to light and air from every side, we find it generally 
assume a compadb, rounded habit ; but if we set it where light 
and air are more or less cut off, as near lofty trees, among 
bushes, or in a thick wood, then two cases are possible. If the 
soil is poor, and if moisture is deficient, the plant will languish 
or even die ; but if the earth be fruitful and moisture abundant, 
it will shoot out long, slender stems, seeking to win its way to 
the light. As gardeners and farmers often say, it will be 
“drawn” by the overtopping objedbs. Thus, then, the very 
circumstances which would render it necessary or desirable for a 
plant to climb, enable it, at any rate, to take the first step, by 
becoming more slender, longer in its joints, and more flexible. 
VOL. VI. (N.S.) P 
