Phylum Opisthokonta [117 



1. Sporangia opening through opercula. 



2. Pluricentric Family 7. Nowakowskiellacea. 



2. Monocentric Family 8. Chytridiacea. 



Family 1. Cladochytriacea [Cladochytriaceae] Schroter in Engler and Prantl Nat. 

 Pflanzenfam. I Teil, Abt. 1: 80 (1892). Family Hyphochytriaceae [Cladochytria- 

 ceae) A. Fischer in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 4: 131 (1892), in 

 part. Family Physodermataceae Sparrow Aq. Phyc. 304 (1943). Pluricentric chytrids, 

 the sporangia not operculate. The members of this family are of the same body type 

 (designated by Karling, 1931, the rhizo mycelium) as the anisochytrid Hyphochy- 

 trium and the Nowakowskiellacea of the present order. In most Cladochytriacea the 

 rhizomycelium includes pairs of swollen cells ("turbinate organs") which give a false 

 appearance of conjugation. There are some forty known species, mostly of two 

 genera, Cladochytrium, saprophytic in vegetable remains, and Physoderma (including 

 Urophlyctis), parasitic in higher plants. Sparrow (1946, 1947) discovered in certain 

 species of Physoderma an alternation of morphologically distinguishable generations, 

 both on the same hosts; the generations are presumably haploid and diploid, but this 

 has not been established by observation of syngamy and meiosis. Polychytrium grows 

 well only on chitin (Ajello, 1948). 



Family 2. Phlyctidiacea [Phlyctidiaceae] Sparrow in Mycologia 34: 114 (1942). 

 Family Sporochytriaceae [Rhizidiaceae, Polyphagaceae) subfamily Metasporeae A. 

 Fischer in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 4: 85 (1892). Monocentric 

 eucarpic chytrids, the centers developed at the ends of filaments which grow from the 

 zoospores, sporangia without opercula. 



These are the most familiar chytrids. There are more than one hundred species. 

 Many are parasitic, on blue-green and green algae, diatoms, pollen grains, nematodes, 

 and other minute fresh-water life; others are saprophytic, on cellulose, chitin, or 

 keratin. Rhizophidium, the most numerous genus; Phlyctidium, Phlyctorhiza, Ento- 

 phlyctis, Diplophlyctis, Loborhiza, etc. 



Family 3. Rhizidiacea [Rhizidiaceae] Schroter in Engler and Prantl Nat. Pflanzen- 

 fam. I Teil, Abt. 1: 75 (1892). Family Sporochytriaceae [Rhizidiaceae, Polyphaga- 

 ceae) A. Fischer in Rabenhorst Kryptog.-Fl. Deutschland 1, Abt. 4: 85 (1892) 

 and subfamily Orthosporeae op. cit. 124. Monocentric eucarpic chytrids, the zoospores 

 enlarging and becoming centers, which in turn become sporangia or presporangia; the 

 sporangia without opercula. A moderate number of species, parasitic on blue-green 

 or green algae, flagellates, or diatoms; or chitinophilous, saprophytic in the shed 

 exoskeletons of insects. Rhizidium, Siphonaria, Asterophlyctis, Polyphagus, etc. 

 Polyphargus Euglenae Nowakowski (1876) is a classic example. The centers lie free 

 in the water, parasitizing cysts of Euglena through freely branching and widely 

 spreading rhizoids. Most centers act as presporangia. Syngamy occurs when a rhizoid 

 from one center makes contact with another center. The protoplasm of the latter 

 migrates into the tip of the rhizoid, which swells and becomes a resting spore. 



Family 4. Synchytriacea [Synchytriaceae] Schroter op. cit. 71. Family Merol- 

 pidiaceae [Synchytriaceae) A. Fischer op. cit. 45. Holocarpic chytrids, the intra- 

 matrical cell unwalled in the vegetative condition, becoming a presporangium or a 

 resting spore, either of which gives rise to a cluster of sporangia. Synchytrium, 

 parasitic on higher plants; Micromycopsis on Conjugatae. 



Family 5. Achlyogetonacea [Achlyogetonaceae] Sparrow in Mycologia 34: 114 

 (1942). Chytrids without rhizoids, the intramatrical center proliferating and pro- 

 ducing a linear series of centers, each of which becomes a sporangium without an 



