108,109.] TRANSFORMATIONS OF THE LEAF. 127 



made of the six upper inflated petioles lying upon 

 the surface of the water like a wheel-shaped raft 

 and sustaining the flower upon its own elevated 

 stalk. 



324. The Tendril is a thread-like, coiling append- 

 age, furnished to certain weak-stemmed plants as their 

 means of support in place. Its first growth is straight, 

 and it remains so until it reaches some object, when 

 it immediately coils itself about it, and thus acquires a 

 firm though elastic hold. This beautiful appendage is 

 finely exemplified in the Cucurbitaceae and Grape, 



396 



if vuufa f r^^r^L&^^m //i ^ 



398 



C96, Leaf of Greenbrier, with tendrils in place of stipules. 397, Leaf ot Everlasting Pea tendrils at end 

 of rachis. 398, Leaf of Gloriosa apex ends in a tendril. 399, Air-bladder of Horn Pondweed. 



above cited ; also in many species of the Pea tribe 

 (Leguminosse), where it is appended to the leaves. It 

 is not a new organ, but some old one transformed and 

 adapted to a new purpose. In Gloriosa superba, the 

 midvein of the leaf is prolonged beyond the blade into 

 a coiling tendril. In the Pea, Vetch, etc., the tendrils 

 represent the attenuated leaf-blades themselves. Again, 

 the entire leaf sometimes becomes a tendril in Lathy- 

 rus, while the stipules act as leaves. 



325. The petiole of the leaf of Clematis, otherwise 

 unchanged, coils like a tendril for the support of the 

 vine. In the Greenbrier, the stipules are changed to 

 tendrils, which thus arise in pairs from the base of 

 the petioles. So probably in the Gourd. 



