176 



STEMS 



(Fig. 151.) Many of the most notable climbers are in the trop- 

 ical regions. . , ,• , e ^ 



Chmbing stems have no more space for. the display ot leaves 

 than prostrate stems have, because one-half of the space for leaf 

 display is cut off by the support; but the cHmbmg position is 

 much better than the prostrate position for escaping the shade 



of other plants. 



One interesting feature 

 of climbing plants is their 

 different ways of climb- 

 ing a support. The Bean, 

 Morning Glory, and Hop 

 climb by twining around 

 the support. They are 

 called twiners. These 

 plants can not chmb a 

 wall, for they must have 

 a support which they can 

 wrap about. {Fig. 162.) 

 The Sweet Pea and Grape 

 Vine illustrate chmbing 

 by means of tendrils 

 which hook about the sup- 

 port. Tendrils are usually 

 modified leaves or stems, 

 although sometimes of 

 doubtful origin. {Fig. 

 153.) In some tendril 

 cUmbers, as in the Japan 

 Ivy, the tendrils have 

 swollen ends which flatten 

 against a wall or other 

 supports, where they se- 

 crete a mucilaginous substance by which they are able to hold 

 on tenaciously. In case of the English Ivy, the plant is held 

 to the wall by roots which are as efficient as tendrils. The 

 Virginia Creeper climbs by means of both roots and tendrils. In 

 being able to climb vertical walls of stone or brick, the Ivies 

 are well adapted for wall vines for which they are much used. 

 {Fig. 154.) 



Fia. 151. — A Grape Vine climbing over 

 a dead Elm tree. 



