CHAPTER XIV 

 THE ALGJE-FUNGI (PHYCOMYCETES) 



197. General characteristics of the fungi. The algae-fungi, 

 as the name suggests, are fungi which resemble the algae. It 

 was noted in the discussion of the bacteria that the fungi are 

 thallophytes which do not possess chlorophyll. Some of the 

 fungi are so much like the algae in general structure that if 

 chlorophyll were added to them they might easily be classi- 

 fied together. There are other fungi which are very unlike 

 the alg83. 



Absence of chlorophyll suggests the absence of ability to 

 manufacture foods from water and carbon dioxide (Sect. 17). 

 In order to live, fungi must secure their carbohydrate food 

 already prepared for them, and the first great question that 

 arises relates to the ways in which non-chlorophyll-bearing 

 plants secure their food. 



198. The dependent habit of living. The dependent habit is 

 characteristic of the fungi, though there are many dependent 

 plants that do not belong to the fungi. Dependency may 

 appear in any one of several forms. Such fungi as toadstools, 

 mushrooms, and puffballs live upon decaying plant and ani- 

 mal material, old leaves, logs, stumps, manure heaps, etc., 

 and when so living are called saprophytes. Sometimes depend- 

 ent plants live upon living plants or animals, as in the case of 

 tree-destroying fungi, wheat rust, and some of the bacteria of 

 the human body. These, as we have seen, are called parasites, 

 and the organism which furnishes the food material is the host. 

 Two living organisms, plant or animal, may live together in 

 such a way that each benefits from the presence of the other, 

 and sometimes these are called mutualists, meaning " mutually 

 helpful," and sometimes they are called helotists, meaning that 



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