GENERAL SYSTEMATIC BACTERIOLOGY 503 



Buchanan (1918, p. 467) gave the following generic diagnosis (in- 

 cluding it as the fourth genus of the tribe Thiocapseae). 



Cell families resembling in grouping and multiplication the cells of the algal 

 genus Aphanocapsa . Cell division occurs in all directions of space, the cells are 

 spherical, with thick confluent membranes, which unite to form a structureless, 

 gelatinous layer. The cells are of a bright rose red color and contain numerous 

 sulphur granules. The cells do not swarm. 



The type species is Thiocapsa roseo-persicina Winogradsky. 



Bcrgey et al. (1923, p. 396) follov/ed Buchanan. 



Thiocapsaceae. A subfamily described by Migula (1900, p. 1042). 

 It includes those sulphur bacteria in which the cells are united into 

 families, and division of the cells takes place in three directions of 

 space. The following genera are included, Thiocystis, Thiocapsa and 

 Thiosarcina. The subfamilj^ is recognized by Migula (1904, p. 146). 

 (1905, p. 163) by Frost (1911, p. 61) and by Molisch (1910). 



Thiocapseae. A tribal designation proposed by Buchanan (1918, 

 p. 467) for the first tribe of the subfamily Chromatioideae with the 

 following description: "Bacteria containing both sulphur granules and 

 bacteriopurpurin. Cells divide in three directions of space, united into 

 families." 



The genera included were Thiocystis, Thiosphaera, Thisophaerion, 

 Thiocapsa and Thiosarcina. 



Bergey et al. (1923, p. 395) used the same description. 



Thiococcus. The third genus of spherical sulphur bacteria of the 

 family Thiohacteriaceae used by Orla-Jensen (1909, p. 330). He 

 mentions as a type a colorless sulphur coccus described by Warming 

 (1876). 



Thiocystis. A genus of sulphur bacteria described by Winogradsky 

 (1888, p. 60) . The spherical cells are massed in small compact families, 

 enveloped singly or several together in a gelatinous cyst, and capable 

 of swarming. Usually 4 to 20 or 30 cells are united into a single family. 

 The cells are light colored, single cells almost colorless. In masses 

 the cells show a beautiful violet or red-violet color. The cells are fre- 

 quently filled with sulphur granules. Thiocystis violacea and Th. 

 rufa were described. 



The genus was included by Trevisan (1889, p. 27) as the sixth of 

 the tribe Ascococcee. 



De Toni and Trevisan (1889, p. 1040) give the following description: 



Cocci globosi vel divisionis tempore globosovoidei, modice numerosi, in muco 

 matricali nidulantes, in familia forma indefinitas, irregulares, parvulas, intus 



