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, Solanum, 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. 



18. To understand how leaves or leafstalks lay 

 its lea&taiks. {jqJ^ ^f ^ 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 will 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 



Fig. 4 Solanum jasminoides, climbing by 



