SECTION J 



1. Cells occur singly; motile bj' meuns of polar flagella; may be encapsulated and ma}' form 



zoogloeaebut if so, do not oxidize hydrogen .sulfide and do not dojxjsit sulfur internally 



2 

 Cells occur singly, in pairs or in short chains; non-motile; individual cells encapsulated 

 and usually contain two pseudovacuoles per cell which makes them buoyant and which 

 may give them a polygonal appearance; sulfur is deposited internally 



Khodothece p. 50 

 Cells occur in well-defined aggregates. When growing in the presence of hydrogen sul- 

 fide, sulfur is deposited internally 4 



2. Hydrogen sulfide is not oxidized. Sulfur is not deposited internally 



Rhodopseudonionas p. 53 

 Hydrogen sulfide is oxidized, and globular sulfur is deposited internally 3 



3. Cells of uneven width and length; often swollen, spindle-shaped and hlamentous 



Khabdoinonas p. 48 

 Cells of uniform width; spherical to cylindrical, the latter sometimes slightly curved 



Chroniatiuni p. 50 

 Note: Single cells of Thioihece, Thiocyslis and Lumprocystis resemble Chro- 

 matium very closely. Also cells of Thiospirillum violaceum are indistinguish- 

 able from curved cylindrical forms of Chromatium. 



4. Cells occur in cubical packets Thiosarcina p. 39 



Cells in young colonies appear as flat sheets in which cells are arranged in parallel rows 



embedded in a capsular material. In an unfavorable position or environment, irregular 



clumping of cells may occur Thiopedia p. 40 



Other than above 5 



5. Individual cells or cell masses embedded in conspicuous capsules or zoogloea 6 



Individual cells or cell masses apparentlj^ devoid of capsular material although cells 



within the mass may be clearly separated in space 7 



6. Cells spherical, occurring in large numbers well separated in a conspicuous common 



slime capsule. In dry conditions the capsular material forms a double contoured 

 membrane around the cells. On moistening, the mass slowly swells and bursts. As the 

 liberated cells divide they form a fiat, spreading colonj' in which the cells are no more 

 than three layers deep but are separated from each other by capsular material 



. Thiocapsa p. 4-1 

 Cells spherical and encapsulated. In the early stages of growth of the colony, cells form 

 in tetrads* resembling those of Thiocyslis. Further division of the cells gives rise to a 

 compact opaque mass of cocci embedded in a large slime capsule. This is followed by 

 formation of arched fragments similar in appearance to sections of a hollow sphere, 

 the fragments being arranged as if on the surface of a sphere within the capsule. Con- 

 tinued growth of the arched fragments results in their edges touching but not coa- 

 lescing. Infolding of the arched pieces takes place, finally almost filling the internal 

 cavity and producing a network resembling a sponge. The enveloping capsule even- 

 tually ruptures, liberating fragments of the zoogloeal network which reorganize into 

 small groups interlinked by single cocci. Under unfavorable conditions the cocci are 

 vacuolated, and sulfur is confined to the peripheral cytoplasm. Free cells are motile 

 (cf. Chromatium) . The total transformation occurs in 40 days 



Lamprocystis p. 43 



* Winogradsky considered that cells which form tetrads divide in three directions, the 

 result being a four-pointed group rather than a fiat group of four. 



1031 



