ROOTS. 



97 



Ail such roots, not developed from the end of the radicle 

 and in a straight line with it, are called secondary or 

 adventitious roots. Under this head should, of course, be 

 placed the fibrous roots of all Monocotyledonous plants, 

 the true primary roots of which are but very feebly 



developed. So, 

 also,all branches 

 of primary roots 

 should be re- 

 garded as adven- 

 titious. When 

 such roots are 

 developed from 

 parts of the stem 

 which are not in 

 contact with the 

 ground, they are 

 aerial, as, for example, the roots developed from the 

 lower joints of the stem of Indian Corn. 



135. There are a few curious plants whose roots never 

 reach the ground at all, and which depend altogether 

 upon the air for food. These are called epiphytes. There 

 are others whose roots penetrate the stems and roots of 

 other living plants, and thus receive their nourishment 

 as it were at second-hand. These are parasitic plants. 

 The Dodder and Beech-drops, of Canadian woods, are 

 well-known examples. Others, again, subsist upon 

 decomposing animal or vegetable matter, and are hence 

 known as saprophytes. Indian Pipe and Coral-root are 

 good examples of saprophytic plants. Both parasites 

 and saprophytes are usually destitute of green leaves, 

 Fig. 126. Adventitious roots of Verbena, 



Fig. 126. 



