CHAPTER XVIII 



THALLOPHYTES : FUNGI 



177. General characters. — In general, Fungi include Thal- 

 loj)hytes wliicli do not contain chlorophyll. From tliis fact 

 it follows tliat they can not manufacture food entirely out 

 of inorganic material, but are dependent for it upon otlier 

 plants or animals. This food is obtained in two general 

 ways, either (1) directly from the living liodies of plants or 

 animals, or (2) from dead bodies or the products of living 

 bodies. In the first case, in which living bodies are at- 

 tacked, the attacking fungus is called a parasite, and the 

 plant or animal attacked is called the host. In the second 

 case, in which living bodies are not attacked, the fungus is 

 called a mproplryte. Some Fungi can live only as i)arasites, 

 or as saprophytes, but some can live in either way. 



P'lingi form a very large assendjlage of plants, much 

 more numei'ous than tlie Alga\ As numy of the jiarasites 

 attack and injure useful plants and animals, producing 

 many of the so-called " diseases," they are forms of great 

 interest, (fovernments and Experiment Stations have ex- 

 jiended a great deal of money in studying the injurious 

 ])arasitic Fungi, and in trying to discover some nietliod of 

 destroying them or of preventing their attacks. JIany of 

 the parasitic forms, however, ai'c barndess ; wliile many of 

 tlie saprophytic forms are decidedly beneficial. 



It is generally supposed that the Fungi are derived from 



the Alga^, having lost their chlorophyll and ]io\vcr of inde- 



])endent living. Some of them reseml)k' certain Alg;e so 



closely that the connection seems very jjlain ; but others 



201 



