Fig. 171. — Macrocystis. The 

 giant kelp of the Pacific coast. 

 This plant often attains a length 

 of several hundred feet. It is 

 one of the brown algae. 



72. Fungi. — These plants 

 have no chlorophyll and 

 therefore are dependent upon 

 other organisms for their supply 

 of food. They are thought to 

 be the descendants of algae, but 

 not the ancestors of any other 

 group. Therefore, in studying 

 the history of plants, they are of 

 less interest to us than algae. 

 But in studying the relations of 



plants to man, they are of far more interest to us than are 



the algse, as you shall see. 



A. Parasites and Saprophytes. — Dependent plants 

 either obtain food di- 

 rectly from other living 

 organisms or use sub- 

 stances for food which 

 were once a part of the 

 bodies of living organ- 

 isms. Those which use 

 the former method of 

 obtaining food are called 

 parasites; those which 

 use the latter are called 

 saprophytes. Note that 

 though all fungi are 

 either parasites or sap- 



Fig. 172. — One of the red seaweeds showing 

 its finely and gracefully divided body. — 

 After Hunter. 



