CHYTRIDIALES 43 



resembling superficially Braun's species of Chytridium, but differing, 

 as did C. saprolegniae (Cornu, 1872a), in the number of flagella on the 

 zoospore, were gradually added to the group. As a result, the "chytrids" 

 soon became a dumping ground for all aquatic Phycomycetes of simple 

 body plan. 



In 1864 de Bary and Woronin recognized the chytrids as constituting 

 a family made up of the genera Chytridium, Rhizidium, and Synchytrium. 

 Cohn (1879: 279) made the group coequal with the Saprolegniales and 

 Peronosporales and it has usually been so regarded by most students 

 of the Phycomycetes. In the well-known monograph by Fischer (1892), 

 however, the Chytridiales are combined with the Ancylistales (now 

 the Lagenidiales) to form the Archimycetes, coequal with the Zygo- 

 mycetes and Oomycetes. This merging of the two groups has been fol- 

 lowed by few subsequent workers, but the term "Archimycetes" has 

 been retained by some and applied to various combinations of lower 

 fungi. Sparrow (1935b) restricted the order to forms with posteriorly 

 uniflagellate zoospores and later (1942; 1943) removed from the old 

 group similar fungi with anteriorly uniflagellate zoospores to the Hy- 

 phochytriaceae, regarded as a family of uncertain affinities. Karling 

 (1943) assembled such anteriorly uniflagellate types in a new order 

 Anisochytridiales, which in the present publication is designated the 

 Hyphochytriales (p. 743). 



The minute and often bizarre fungi belonging to the Chytridiales 

 occur predominantly in fresh waters, although, as earlier indicated, 

 a few live in the ocean and many more in soils in terrestrial or semi- 

 terrestrial habitats. In fresh water they most often appear on algae, 

 other aquatic Phycomycetes, spores and decaying parts of higher plants, 

 on microscopic animals and their eggs, in the empty exuviae of certain 

 aquatic insects, and on keratinous, chitinous, and cellulosic materials 

 from which they have been taken by baiting. Of the relatively few 

 marine species now known nearly all have been discovered on sea- 

 weeds; one as yet little-understood marine form has been recorded 

 from the ductless kidney of ascidians. Some are obligate parasites of 

 phanerogams. Chytridiaceous fungi have been found wherever they 

 have been searched for by trained observers and are probably world- 

 wide in their distribution. At present the best-known areas are western 



