CHAPTER XI 



PHYCOMYCETOUS AFFINITIES OF THE 

 HEMIASCOMYCETES 



In the foregoing treatment of the Phycomycetes it has been 

 emphasized (p. 21) that there are two well known opposing 

 theories as to the origin of the fungi. One of these treats the 

 group as an aggregation of relatively unrelated parts, which 

 have degenerated along different lines from widely separated 

 subdivisions of the algae. The other maintains that the fungi 

 are monophyletic, and have arisen from non-chlorophyll bearing 

 organisms lying below the level of the lowest of the present day 

 Phycomycetes. 



Advocates of the former theory regard the Phycomycetes and 

 Ascomycetes as only remotely related, and believe the simplest 

 of the Ascomycetes to be degenerate forms which have been 

 derived in relatively recent times from more complex Asco- 

 mycetes. Adherents of the other theory maintain that the 

 higher fungi have had a phycomycetous ancestry, and regard 

 the simplest of the Ascomycetes as primitive and clearly related 

 to certain of the higher Phycomycetes. In order that this 

 latter point of view might be adequately presented for the con- 

 sideration of the student interested in phylogeny it has been 

 necessary to incorporate in the book the material composing this 

 final chapter. This inclusion has been desirable from the 

 standpoint of taxonomy also, since some of the forms treated by 

 various authors as simple Ascomycetes are at best doubtful 

 members of that group, and may be regarded by other writers as 

 belonging to the Phycomycetes. 



The essential features of the Ascomycetes have been enumer- 

 ated above (p. 16) in the introductory chapter, and require 

 little elaboration here. It should be recalled that the group 

 is distinguished by the ascus, a sac-Hke cell forming endogenous 

 spores called ascospores, usually in small and definite number 

 (typically eight, less frequently some other multiple of two). 

 It should be remembered too that the ascus and sporangium 



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