Fig. 55. Sulfur bacteria. — 1. Beggiatoa alba, (o) A filament rich in sulfur 

 granules; (6' and c) Filaments showing the gradual disappearance of the 

 sulfur; X 900. 2. Filaments dying for lack of sulfur; X 900. 3. Thiothrix 

 tenuis; X 100. 4. Motile filament of Thiothrix tenuis; X 900. 5. Thio- 

 dictyon elegans; X 900. 6. Thiothece gelaiinosa; X 900. 7. (a) Chromatium 

 Weissii; (b) Chromatium Okfmii; (c) Rhabdochromatium roseum; (d) Rhab' 

 dochromatium fusiforme; X 900. (All after Winogradski.) 



