108 



STRUCTURAL BOTANY. 



presjsly contrived, as if by art, for holding water. The pitchers 

 of Sarracenia, whose several species are common in bogs North 

 and South, are evidently formed by the blending of the involute 

 margins of the broadly winged petioles, so as to form a complete 

 vase. The broad expansion which appears at the top may be 

 regarded as the lamina. These pitchers contain water, in which 

 insects are drowned, being prevented from escaping by the de 

 flexed hairs at the mouth. Other pitcher-bearing plants are 

 equally curious ; as Darlingtonia of California, Nepenthes and 

 Dischidia of the East Indies. In Dionasa of North Carolina, 

 the leaves are transformed to spiny, snapping fly-traps ! 



323. Many weak-stemmed water-plants are furnished with Air- 

 bladders, or little sacks filled with air to buoy them up near to 

 the surface. Such are the bladders of the common Bladderwort, 

 formed from the leaf-lobes. In the Horned-bladderwort, the 

 floats are 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. 



396 



398 



396, Leaf of Greenbrier, with tendrils in place of stipules. 397, Leaf of Everlastinsr Pea tendrils at end 

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



324. The Tendril is a thread-like, coiling appendage, fur- 

 nished 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 Cucurbitacese and Grape, 

 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 



