62 THE PHYCOMYCETES 



In the present account the Phycomycetes are divided into 11 

 orders: Chytridiales, Lagenidiales, Blastocladiales, Monoblephari- 

 dales, Leptomitales, Saprolegniales, Pythiales, Albuginales, Per- 

 onosporalesj Mucorales, and Entomophthorales. Some workers 

 do not recognize all these as of ordinal rank, although no one 

 questions that all are Phycomycetes. Some students would include 

 in addition the Endogonales and Eccrinales, but the classification 

 of both of these orders in the Phycomycetes remains of doubtful 

 justification. 



Origin of the Phycomycetes. There are three points of 

 view among botanists regarding the origin of the Phycomycetes. 

 The first of these, which is the oldest, is that they are degenerate 

 algae and that consequently in classifications they should be in- 

 cluded among the Algae. Some of the workers who hold to this 

 concept treat the Phycomycetes and Algae as taxonomically dis- 

 tinct, largely as a matter of convenience. This viewpoint was 

 elaborated by Professor Charles E. Bessey. 



The second point of view is that the Algae and Fungi have 

 evolved as two parallel series, a phylogenetic approach advocated 

 by Professor G. F. Atkinson. For the student who is interested 

 in phylogeny the evidence and arguments for and against both 

 of these opposed viewpoints are succinctly presented in a paper 

 by Atkinson (1909). 



The third viewpoint is that the Phycomycetes are derived from 

 the Protozoa and should be placed in a phylum distinct from the 

 Algae. Arguments for the validity of any of these points of 

 view rest seemingly upon somewhat the same sort of founda- 

 tion as do those for political or religious beHefs. 



LITERATURE CITED 



Atkinson, G. F., "Some problems in the evolution of the lower fungi," 

 A?i?j. My col, 1:^^\-An, 1909. 



Couch, J. N., "The structure and action of the cilia in some aquatic Phy- 

 comycetes," Am. J. Botany, 25:704-713, 1941. 



Sparrow, F. K., Aquatic Phycomycetes, exclusive of the Saprolegniaceae 

 and Pythium. xx + 785 pp. The University of Michigan Press. 1943. 



Wolf, F. A., and Ruth M. McLean. "Sporangial proliferation in Perono- 

 spora tabacina,'' Phytopathology, 30: 264-268, 1940. 



