468 R. E. BUCHANAN 



Cells ellipsoidal, dividing at first in three planes to form sphericcd 

 cell masses, later in two planes, forming hollow sacks in which the 

 cells lie embedded in a layer in the walls, finally the membrane 

 ruptures, and the whole mass becomes net like, much as in the algml 

 genus Clathrocystis. Usually colored intensely violet. Small sulphur 

 granules present. Capable of swarming. 



The type species is Lamprocystis roseo-persicina (Cohra} 

 Schroeter. 



Tribe III. Thiopedieae Trib. nov. 



Synonyms : 



Thiopediaceae Migula, 1900, p. 1044 



Sulphur bacteria in which the cells are united into families, and 

 cell division is in two directions of space, resulting in the develo'p- 

 ment of plates of cells. 



The two genera may be differentiated by the following key- 



Key to the genera of Thiopedieae 



A. Cells occurring regularly in fours Genus I. Lam-prirpediia 



B. Cells occurring in a film or membrane, not regularly disposed in tetrads. 



Genus II. Thiodertma 



p 



Genus I. Lampropedia Schroeter, 1886, p. 151 



Synonyms : 



Erythroconis? Oersted, 1842, p. 6 

 Thiopedia Winogradsky, 1888, p. 85 



Cells united into tetrads, forming flat tubular masses. Contain 

 sidphur granules and bacteriopurpurin. 



The type species is Lampropedia hyalina (Kuetzing) SchroeteT. 



Genus II. Thioderma Miyoshi, 1897, p. 170 



Cells spheroidal, light rose in color, containing small, incom- 

 spicuous, sulphur granules. United into thin purplish membrane., 

 The type species is Thioderma roseum Miyoshi. 



