CHYTRIDIALES 107 



6. Urophlyctis Schroter (Jahresber. Schles. Gesell. f. Vaterl. 

 Ciiltur, 60: 198, 1882). 

 The present status of the genus Urophlyctis is indicated in the 

 above discussion of Physoderma. Some of the species of the 

 genus are limited to the underground portions of their host, 

 while others occur only in the parts above ground. Some exert 

 a dissolving action on the cells of the host and develop a wide- 

 spreading mycelium; others are limited to the cells originally 

 infected by the swarmspores. Eight species are included in the 

 genus by von Minden. The following are known to occur in 

 North America. 



U. pulposa (Wallroth) Schroter (Fig. 38, c) — in Atriplex and Chenopodium. 

 U. alfalfae (Lagerheim) Magnus (Fig. 36, 37, s) — in Medicago (Wilson 

 1920). 



U. pluriannulatus (B. & C.) Farlow (Fig. 37, t) — in Sanicida. 

 U. major Schroter — in Rumex. 



Doubtful Chytridiales 



1. Hyphochytrium Zopf (1884: 187). 



syn. Hyphophagus v. Minden (1911: 420). 

 Those chytrids in which the mycelium is described as of con- 

 siderable diameter were brought together in the family Hypho- 

 chytriaceae by Schroter (1892: 83). He included the genera 

 Catenaria, Hyphochytrium, Polyrhina, and Tetrachytrium. Later 

 von Minden (1911: 383) used the family name but excluded 

 Hyphochytrium, the family as formed by him embracing Macro- 

 chytrium, Zygochytriwm, and Tetrachytrium. There seems to be 

 no sound basis for the recognition of the family and it is here 

 discarded. The genus Hyphochytrium contains a single species, 

 H. infestans Zopf (Fig. 39), parasitic in the apothecia of Helotium. 

 The mycelium is rather broad, richly branched, of uniform 

 diameter, and occasionally septate. Sporangia are formed 

 from terminal or intercalary swellings. The swarmspores are 

 uniciliate. Resting spores are unknown. 



2. Tetrachytrium Sorokin {Botaii. Zeitung, 32 : 307, 1874). 



This genus, based on the single species, T. 'triceps Sorokin 

 (Fig. 40), is known only from the original description and figures. 

 It is included in the Hyphochytriaceae by Schroter (1892: 83) 

 and von Minden (1911: 387). 



