ORGANS OF NUTEITION. 



101 



case the woody stem has received the name of sarmentum. In 

 tropical climates these woody climbing or twining stems often 



Fiff. 196. 



Fiff. 195. 



Fig. 195. Climbing stem of the 

 Ivy. a, a. Aerial roots. 



Fig. 197. 

 Stem of Convolvulua. 



Fig. 196. Stem of Honeysuckle. 



occur ; they are called lia7ias, and they frequently ascend to the 

 tops of the loftiest trees, and then either descend to the ground 

 again, or run to the branches of neighbouring trees. 



The stem has received many names according to its natuie. 

 „<^hus it is called a caulis in plants which are herbaceous, or die 

 down annually ; a trunk as in trees, where it is woody and per- 

 ennial; a culm as in most Grasses and Sedges, where it presents 

 a jointed appearance; and a, caudex or stijje as in Tree-Ferns 

 and Palms. 



From the nature, duration, and mode of ramification of 

 stems, plants have been divided from the earliest periods into 

 three classes, called, respectively, Herbs, Shrubs, and Trees. 

 Thus, those plants which have stems that die down annually to 

 the surface of the ground are called herbs ; while those which 

 have perennial aerial woody stems are denominated trees or 

 shrubs, according to circumstances. Thus the term tree is 



