FAMILY I. CHLAMYDOBACTERIACEAE 265 



1. Trichomes 1 to 3 microns thick. 



1. Lcplothrix ochrncea. 



2. Trichomes 0.4 to 0.5 micron thick. 



2. Leptothrix thermnlis. 

 B. Trichomes attached. 



1. Attachment is by means of a hoklfast. 



a. Trichomes arise singly, each from its own holdfast. 



b. Sheath very thin, encrusted only at the base of the trichome. 



3. Leptothrix sideropons. 

 bb. Sheaths thick. 



c. Trichomes showing no or only a few false branches. Cells up to 1 

 micron thick. 



4. Leptothrix discophora . 



cc. Trichomes always with numerous false branches. Cells 1.4 microns 

 thick. 



5. Leptothrix major. 



aa. Numerous trichomes arising from a common holdfast. 



b. Sheaths not tapering to the tip. Trichomes form sessile, hemispherical 

 clusters. 



6. Leptothrix lopholea. 



bb. Sheaths tapering to the tip. Trichomes usually form free-living colonies 

 in which the trichomes radiate like the spokes of a wheel. 



7. Leptothrix echinata. 



2. Attached by gelatinous masses. 



8. Leptothrix epiphytica. 



II. Trichomes spirally twisted (except in a variety of Leptothrix pseudovacuolata). 



A. Epiphytic, growing twisted around thread-like algae. 



9. Leptothrix voluhilis. 



B. Free-living in water or on the surface of mud. 



1. Trichomes very thin; sheaths tapering slowly to the tip, ending in a sharp point. 



a. Cells 0.3 micron in diameter. 



10. Leptothrix skujae. 

 aa. Cells 0.9 micron in diameter. 



11. Leptothrix winogradskii. 



2. Trichomes thick, sometimes not twisted; sheaths rounded at the tip. 



12. Leptothrix pseudovamwlata. 



1. Leptothrix ochracea (Roth, 1797) rounded by a delicate sheath which later 



Kiitzing, 1843. {Conferva ochracea Roth, becomes yellow to brown in color. Sheath 



Catal. bot. I, 1797, Table V, Fig. 2; also see alveolar, completely dissolving in dilute 



Dillwyn, Syn. Conf., 1802, Table 62; Kiit- hydrochloric acid. When the sheath becomes 



zing, Phycologia generalis, 1843, 198.) very thick, the trichomes slip out of the 



o.chra'ce.a. Gr. noun ochra j-ellow ochre; sheath and secrete a new one so that many 



M.L. adj. ochraceus like ochre. empty sheaths are found. Presumably polar 



Description taken from Kiitzing (loc. cit.) flagellate swarm cells have been observed, 



and Cataldi (Estudio Fisiologico y Siste- Not acid-fast. Gram-negative, 



mdtico de Algunas Chlamydobacteriales. Gelatin: No liquefaction. 



Thesis, University of Buenos Aires, 1939, Iron citrate and ammonium agar colonies: 



58 and 66). Filamentous and spreading, with wavy 



Cells rod-like, colorless, 0.8 to 1.0 micron. edges. 



Motile. Trichomes long, free-floating, never Manganese acetate agar colonies: Fila- 



attached to a substrate, never branching, 1 mentous, not very large, 



micron in thickness. Young trichomes sur- Iron citrate and ammonium agar slant : 



