SOME OTHER TYPES OF INDIVIDUAL ORGANIZATION 



201 



athlete's foot in man, the smuts and rusts that attack higher plants (some 

 of which alternate between two different hosts, Fig. 33.2), and certain 

 mushrooms and bracket fungi which are parasitic upon living trees. 



A few kinds of fungi have become adapted to symbiotic existence with 

 green plants. The best known examples are furnished by the lichens 



Fig. 13.16. The Indian pipe, a colorless saprophytic flowering plant. (Courtesy Ward's 

 Natural Science Establishment, Inc.) 



(Fig. 33.3), which are made up of intermingled cells of a fungus and a 

 green alga. The alga can live alone, while the fungus cannot; but the 

 association is not one of parasitism. The fungus absorbs soil moisture and 

 mineral substances; the alga shares these, and by photosynthesis pro- 

 duces food of which a part is used by the fungus. Another symbiotic 

 relation which has great importance for soil fertility is that which exists 

 between certain of the nitrogen-fixing bacteria and plants of the bean 



