FAMILY I. THIORHODACEAE 43 



and carotenoid pigments, coloring the cell masses purplish to red. Capable of photosyn- 

 thesis, in the presence of hydrogen sulfide, whereby elemental sulfur is formed as an inter- 

 mediate oxidation product which is deposited as droplets inside the cells. 

 The type species is Thiocystis violacea Winogradsky. 



Key to the species of genus Thiocystis. 



I. Individual cells more than 2 microns in width. 



1. Thiocystis violacea. 

 II. Individual cells about 1 micron or less in width. 



2. Thiocystis rufa. 



1. Thiocystis violacea Winogradsky, taining hydrogen sulfide and exposed to 



1888. (Schwefelbacterien, Leipzig, 1888, 65.) light; sulfur springs. 



vi.o.la'ce.a. L. adj. violaceus violet- Illustrations: Zopf, Zur Morphologie der 



colored. Spaltpflanzen, Leipzig, 1882, PI. V, fig. 12; 



Cells about 2.5 to 5.5 microns in diam- Winogradsky, op. cit., 1888, 65, PI. II. Fig. 



eter, spherical to ovoid. Swarmers actively 1-7. 



motile by means of polar flagella. 



^ , . f, 1, . . , , 2. Ihiocystis rufa vVmogradsky, 1888. 



Colonies: Small, inside a common capsule, f lu + • t • • looo /=\ 



containing not over 30 cells. Several such 



colonies form loosely arranged aggregates, 



most characteristically composed of about _, , , n i , ^i. • ., , 



,- ^ _„ , . . • 1 IT., Color red, usually darker than in the type 



10 to 20 colonies in a single capsule. The re- . ' ,/ n «• j • l 



(Schwefelbacterien, Leipzig, 1888, 65.) 

 ru'fa. L. adj. rujus red, reddish. 

 Cells less than 1 micron in diameter. 



suit is a nearly spherical zoogloea. In small 



colonies, the cells appear as rather distinct ""oT bl*'"k 



species. When the cells are stuffed with 

 sulfur globules, the aggregates appear al- 



tetrads; in larger colonies, the cells become 



The common gelatinous capsule usually 



somewhat compressed and the tetrad-like .obtains a far greater number of closely 



arrangement may be lost. p^^j^^^ individual colonies than is the case 



In pure cultures, the species often fails to Jq Thiocystis violacea. 



produce the characteristic capsules; the or- Habitat: Mud and stagnant water con- 



ganisms then occur as actively motile single taining hydrogen sulfide and exposed to 



cells or diplococci, with little or no slime light; sulfur springs, 



formation. No pseudocapsules are formed. Illustration: Winogradsky, loc. cit., PI. 



Habitat: Mud and stagnant water con- II, fig. 8. 



Genus VII. Lamprocystis Schroeter, 1886. 



(In part, Clathrocystis Cohn, Beitr. Biol. Pfl., /, Heft 3, 1875, 156; in part, Cohnia Winter, 

 in Rabenhorst, Kryptogamen-Flora, 2 Aufl., 1884, 48; not Cohnia Kunth, Enumeratio plan- 

 tarum, 5, 1850, 35; Schroeter, Die Pilze Schlesiens, in Cohn, Kryptogamen-Flora von 

 Schle-sien, 3, 1, 1886, 151.) 



Lam.pro.cys'tis. Gr. adj. lamprus bright, brilliant; Or. noun cystis the bladder, a bag; 

 M.L. fem.n. Lamprocystis a brilliant bag. 



Sulfur purple bacteria which form more or less large aggregates of cells enclosed in a 

 common gelatinous capsule. Individual cells spherical to ovoid. Small aggregates closely 

 resemble those of Thiocystis, even to the extent of the tetrad-like arrangement of cells in 

 the small colonies. Behavior of the large aggregates during development appears to be 

 different; the small individual cell groups or colonies do not emerge from the slime capsule 

 until the initially relatively compact cell mass becomes broken up into smaller clusters, 

 these eventually forming a somewhat net-like structure. This behavior has been ascribed 

 to a change in the mode of cell division which at first appears to take place in three per- 

 pendicular planes and later presumably changes to a division in only two directions. Cells 



