50 LEAF-CLIMBERS, Cuap, IT. 
Nevertheless, the main service of the revolving move- 
ment is to bring them into contact with surrounding 
objects, which are slowly but securely seized. The 
young petioles, which alone are sensitive, have their 
ends bowed a little downwards, so as to be in a slight 
degree hooked ; ultimately the whole leaf, if it catches 
nothing, becomes level. I gently rubbed with a thin 
twig the lower surfaces of two young petioles; and in 
2hrs. 80m. they were slightly curved downwards; in 
5 hrs., after being rubbed, the end of one was bent 
completely back, parallel to the basal portion ; in 4 hrs. 
subsequently it became nearly straight again. To 
show how sensitive the young petioles are, I may 
mention that I just touched the under sides of two 
with a little water-colour, which when dry formed 
an excessively thin and minute crust; but this 
sufficed in 24hrs. to cause both to bend downwards. 
Whilst the plant is young, each leaf consists of three 
divided leaflets, which barely have distinct petioles, 
and these are not sensitive; but when the plant is 
well grown, the petioles of the two lateral and terminal 
leaflets are of considerable length, and become sensi- 
tive so as to be capable of clasping an object 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 
