- 1. Trichomes 1 to 3 microns thick.
1. Leptothrix ochracea.
- 2. Trichomes 0.4 to 0.5 micron thick.
2. Leptothrix thermnlis.
- B. Trichomes attached.
- 1. Attachment is by means of a holdfast.
- 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 pseudovacuolata.
1. Leptothrix ochracea (Roth, 1797) Kützing, 1843. (Conferva ochracea Roth, Catal. bot. I, 1797, Table V, Fig. 2; also see Dillwyn, Syn. Conf., 1802, Table 62; Küt- zing, Phycologia generalis, 1843, 198.)
o.chra'ce.a. Gr. noun ochra yellow ochre; M.L. adj. ochraceus like ochre.
Description taken from Kützing (loc. cit.) and Cataldi (Estudio Fisiologico y Siste- mático de Algunas Chlamydobacteriales. Thesis, University of Buenos Aires, 1939, 58 and 66).
Cells rod-like, colorless, 0.8 to 1.0 micron. Motile. Trichomes long, free-floating, never attached to a substrate, never branching, 1 micron in thickness. Young trichomes surrounded by a delicate sheath which later becomes yellow to brown in color. Sheath alveolar, completely dissolving in dilute hydrochloric acid. When the sheath becomes very thick, the trichomes slip out of the sheath and secrete a new one so that many empty sheaths are found. Presumably polar flagellate swarm cells have been observed, Not acid-fast. Gram-negative,
Gelatin: No liquefaction.
Iron citrate and ammonium agar colonies: Filamentous and spreading, with wavy edges.
Manganese acetate agar colonies: Filamentous, not very large,
Iron citrate and ammonium agar slant:
