ELEMENTS OK STRUCTURAL BOTANY. 



C7 



themselves by clinging to any suppoH that may happen 

 to be within their ve&zh. In some instances the stem 

 itself winds round the support, assuming a spiral form, 

 as in the Morniug-Glory, the ilop, and the Bean, and 

 is therefore distinguished as tmnvuj. In other cases 

 the stem puts forth thread-like leafless branches called 

 tendrils (Fig. 97), which grasp the 

 support, as in the Virginia Creeper, 

 the Grape, and tlie Pea (Fig. 98), or 

 sometimes the leaf-stalks serve the 

 same purpose, as in the Clematis or 

 Virgin's Bower. In these cases the 

 stems are said to climb. 



The stems of wheat and grasses 

 generally are known as culms. They 

 are jointed, and usually hollow except 

 at the joints. 



91. Besides the stems which grow above ground, there 



i 



Fig. 08. 



5is. 99. 



are vaiieties to be found below tlie surface. Pull up a 



