CHAPTER XIII 



THE FUNGI 



Mode of Life. The fungi differ from all the plants thus far 

 studied in that they lack the green pigment chlorophyll, which 

 enables the algae and the higher spore and seed plants to manu- 

 facture their own organic foods from carbon dioxide, water, and 

 salts derived from the soil. The fungi are therefore dependent 

 plants, living either as saprophytes, upon lifeless organic matter, 

 or as parasites, upon living animals and plants. 



Saprophytes. The greater number of fungi, including the 

 familiar mushrooms, molds, and yeasts, are saprophytes, which 

 feed upon and consume lifeless organic bodies or their products. 

 Such fungi serve a useful purpose as scavengers, since they tend 

 to dispose of the dead remains of plants and animals, which 

 might otherwise hinder the growth or imperil the life of other 

 living organisms. This is especially evident in a forest, where 

 saprophytic mushrooms, leaf molds, and bacteria convert the 

 annual fall of leaves, tree trunks, and branches into the ingredi- 

 ents of leaf mold, which is a characteristic component of the 

 forest soil. The accumulation of this annual leaf fall would 

 be disastrous to the living trees and plants of the forest if it 

 did not constantly disappear by decay through the agency of 

 saprophytic fungi. 



Parasites. The parasitic fungi are less numerous than the 

 saprophytes. They include such forms as the bacteria of disease, 

 the parasitic rusts and smuts of cereal grains, and the tree- 

 killing fungi. Such parasites cause immense damage annually 

 through the death of animals and the destruction of valuable 

 crops and timber upon which they prey. 



Classification. The fungi have undoubtedly sprung from the 

 algae by the loss of chlorophyll and chloroplasts, since they so 



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