274 LIFE HISTORIES AND EVOLUTION OF THE FUNGI 



process. The cluster-cup stage is omitted entirely in some of 

 the rusts and in all of the smuts, and there are likewise no 

 traces of it in the higher basidia fungi (Eiibasidiomycetes). 

 Sexual degeneration in these forms, then, has apparently been 

 carried so far that the sexual organs have disappeared entirely 

 from the life histories. 



281. The origin and evolution of the fungi. The study of the 

 evolution of the fungi must be taken up for each of the larger 

 classes separately, for there is every probability that each has had 

 an independent origin from widely separated groups of the algre. 

 The bacteria have probably been derived from the blue-green algse. 

 The higher alga-like fungi (molds, water molds, and blights) 

 apparently show relationships to the siphon algae. Some authors 

 believe that the sac fungi have come from the red algse. The 

 origin of the basidia fungi is very much in doubt and that of 

 the yeasts also, although it is generally held that the latter are 

 degenerate forms from some of the higher fungi. The evolu- 

 tion of the fungal forms in each group becomes very complicated, 

 because the fungi have such wonderfully varied habits resulting 

 from their parasitic and saprophy tic ways of living. In fact, these 

 life habits have produced the greatest variety of structures and 

 adaptations known in any group of spore plants. Still more 

 remarkable, perhaps, is the widespread tendency towards sexual 

 degeneration, which is also believed to be associated with the 

 parasitic and saprophytic life habits. 



