14 
HOW PLANTS CLIMB. 
plants of the same family, with simple leaves, climb freely in this way, neatly 
coiling their leafstalk round any slender support within reach. The vignette 
title-page shows two illustrations of this, in the lower part. 
16. A rather common cultivated species of 
Nightshade, Solarium jasminoides, is a good ex- 
ample of the same kind, and furnishes the 
present illustration, in Fig. 4. It is interesting 
to notice how the leafstalks of this plant which 
have clasped a support grow much stouter and 
firmer than those which have not, becoming 
three or four times as thick as before, — as if 
the need of greater strength and rigidity some- 
how brought it about. 
17. A leaf-climber has this advantage over a 
twiner, that it may reach a given height with 
less amount of substance. Its stem may rise 
straight up, and save much in length over the 
twiner, which has to produce twice or thrice that 
length of stem in reaching the same elevation, on 
account of the coils. 
Fig. 4. Soianum jasminoides, climbing by 18. To understand how leaves or leafstalks lay 
its leafstalks. hold of a support, we must refer back to the Sen- 
sitive Plant (Paragraph 2) ; its leaves and leafstalks, we know, respond to the 
touch of a foreign body by a movement. So do those of leaf-climbers : only the 
movement by which they clasp the support is very slow and incited only by pro- 
longed contact. If one of these leafstalks be rubbed for some time with a piece 
of wood, it will generally respond to the irritation by curving ; but it wdll be two 
or three days about it ; and in two or three days more it may straighten itself, 
unless the stick is left in contact with the leafstalk : then it will clasp it perma- 
nently, making one or perhaps two turns around it, and in time it may thicken 
and harden. That the climbing in such cases is the result of a movement, how- 
ever slow, under sensitiveness to touch, is further shown by the behavior of 
tendrils. 
19. Between leaf-climbing and tendril-climbing there is every gradation. In 
Gloriosa, a tropical plant of the Lily Family, the tip of a simple leaf extends 
