CHAPTER XXII 



THE FUNGI AND THEIR RELATION TO FERMENTATION 

 AND DISEASE 



250. The fungi.* The fungi are thallophytes whose plant 

 bodies have no chlorophyll or other coloring matter capable 

 of doing the work of photosynthesis. Consequently fungi are 

 unable to manufacture the primary foods of plants, such as 

 starch, and are absolutely dependent upon organic substances 

 obtained from animals and plants. Fungi must therefore live 

 either as parasites upon living plants or animals, called their 

 hosts, or as saprophytes (meaning decay plants) upon dead organic 

 matter or the products of decay. Fungi are frequently spoken of 

 as colorless plants, because they have no chlorophyll, but many 

 forms are brilliantly colored by special pigments. 



The fungi have undoubtedly been derived from the algae, 

 not from a single group of the algae, however, but from several 

 widely separated groups. Consequently the classes of the fungi 

 have not developed one from another, but in most cases are 

 believed to be either of entirely independent origin or of very 

 remote relationship through ancient forms of algae no longer 

 living. The chief peculiarities of the structures and life histo- 

 ries of fungi are largely the results of their adaptations to lives 

 of parasitism or saprophytism. One of the results of these adap- 

 tations has been the development of a much greater number of 

 species than is found in the algae. 



* To THE INSTRUCTOR : As in the account of the algae, this chapter describes 

 more forms than should be given in a general course. Many of them must 

 be omitted or merely discussed in the class. They have been included in order 

 to provide a range of material for selection adaptable to various sections of 

 the country and the different conditions under which the subject must be 

 presented. 



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