184 



A TEXTBOOK OF BOTANY [Ch. IV, 10 



While the upright self-supporting condition is typical in 

 foliage-supporting stems, modifications thereof occur in 

 connection with special habits. Most prominent are climb- 

 ers, which make Use of trees, rocks, walls, and other supports 

 to lift their foliage to the light. Being thus supported, they 

 need no great thickness and remain slender, devoting their 



Fig. 126. — A typical epiphytic Orchid, showing aerial roots, and the 

 pseudo bulbs, or storage stems, from which spring true leaves. (Reduced 

 from Kerner.) 



material to increase in length. Some simply clamber over 

 other plants, as in case of the Rattan Palm already men- 

 tioned (page 113) or the many great lianas of the tropics, or 

 the Clematis of our woods. Such plants possess hooks (Rat- 

 tan), twining petioles (Clematis, Fig. 51), or other arrange- 

 ments preventive of slipping from the supporting vegetation. 

 Others, forming our principal vines, cling to a support, either 

 by tendrils, as in Grape and Passion Vine (Fig. 136), or by 



