760 AQUATIC PHYCOMYCETES 



HYPHOCHYTRIUM Zopf 



Nova Acta Acad. Leop.-Carol., 47: 187. 1884 



(Fig. 55 H-I, p. 752; Fig. 56, p. 761) 



Hyphophagus (Zopf) Minden, Kryptogamenfl. Mark Brandenburg, 5: 420. 

 1911 (1915). 



Mycelium isodiametric, relatively broad, branched, extensive, with 

 occasional cross walls, ramifying within the substratum ; sporangia aris- 

 ing as terminal or intercalary swellings of the mycelium, from which 

 they are cut off by cross walls; zoospores anteriorly uniflagellate, plasma 

 without a prominent globule, either escaping fully or partly formed 

 through a pore produced upon the deliquescence of a portion of the 

 sporangium wall or cleaved out at the orifice of a discharge tube; resting 

 spore thick-walled. 



On fresh-water algae, ascocarps of Discomycetes, and moribund 

 stems of maize. 



Zopf's fungus was considered by Vuillemin (1907) to be a filamentous 

 fungus parasitized by a chytrid. On this basis Minden placed it in a new 

 genus, Hyphophagus of the Cladochytriaceae, retaining, however, the 

 name Hyphochytriaceae Schroeter for a family including Macrochyt- 

 rium, Zygochytrium, and Tetrachytrium. No valid reason exists for the 

 substitution of Minden's generic name for Zopf's, particularly since 

 Valkanov (1929b) and Karling (1939b) have reaffirmed in related species 

 Zopf's observations on the flagellation of the zoospore and ascertained 

 that the sporangial and vegetative stages belong to the same organism. 



KEY TO THE SPECIES OF HYPHOCHYTRIUM 



Vegetative system richly branched; in ascocarps of Helotium, in mori- 

 bund tissues of maize, or in internodes of Char a and Nitella 

 Sporangium with an apiculus, discharging fully formed zoospores 



through a lateral pore; in Helotium H. infestans, p. 761 



Sporangium without an apiculus, zoospores formed outside the spo- 

 rangium, the protoplasmic mass discharged through a tube; in 

 moribund tissue of maize and internodes of Char a and Nitella 



H. catenoides, p. 762 

 Vegetative system sparingly branched ; in Hydrodictyon H. hydrodictii, p. 763 



