PHYCOMYCETES 39 



recently published book by Gaumann and Dodge (1928) is a 

 translation of this work of Gaumann. No attempt will be 

 made at this point to criticize or explain the various pronounced 

 changes advocated by Gaumann. In some cases this is done on 

 the pages which follow in connection with the groups concerned. 



In presenting the ordinal and family separations which appear 

 in the present work the writer has tried to maintain a conserva- 

 tive point of view. Changes from the older established arrange- 

 ments have been made only when they were clearly unavoidable. 

 In such cases adequate explanations have been given. The 

 inclusion of the Plasmodiophoraceae in the Chytridialcs and 

 the recognition of the order Blastocladiales constitute instances 

 of this sort. On the whole the classification does not depart 

 far from the older established points of view. The terminations 

 -ales and -aceae for ordinal and family names respectively are 

 those recommended by the International Rules of Botanical 

 Nomenclature (Briquet 1912). They are now generally used 

 in the taxonomic literature. 



Though the eight orders into which the Phycomycetes are 

 separated in the following key constitute rather definitely 

 delimited groups, they tend to merge somewhat at their border 

 lines. This is to be expected in any natural system. If the 

 sum total of the characters of each group be taken into consid- 

 eration the lines of separation will appear more sharp. 



Key to Orders of Phycomycetes 



I. Mycelium wholly absent in several families, in others present but poorly 

 developed or evanescent; thallus at maturity functioning in large part 

 or in its entirety in reproduction; sexual reproduction often unknown, 

 when present of various kinds but not typically oomycetous or 

 zygomycetous. 



A. Thallus in most forms functioning essentially in its entirety in one 



capacity, at maturity usually acting as a single sporangium or 

 gametangium or by cleavage becoming a sorus of like sporangia ; 

 resting spore not lying free in the gametangium. 



1. Chytridiales, p. 43 



B. Thallus at maturity divided by transverse septa into a chain of 



cells capable of functioning in various capacities, i.e., as sporan- 

 gia, male or female gametangia, or specialized vegetative cells; 

 resting spore lying free in the female gametangium and resem- 

 bling the oospore of higher orders; an oospliero apparently lacking. 



2. Ancylistales, p. 117 



II. Mycelium well developed, not evanescent; thallus at maturity function- 

 ing in relatively small part in reproduction; specialized cells cut off by 



