(See note on Leptoihrix and Thiothrix {vide supra 7 and 10).) Trichomes 12 12. Trichomes attached; free cells formed bj' abstriction from the terminal portion are motile by a gliding action on a solid surface Leucothrix p. 850 Note: Although Harold and Stanier claim that Leucothrix does not form a sheath, they consider it to be identical with Pontothrix, which was originally recorded as a sheathed organism. Not as above; if motile, whole trichomes move; cells within the trichomes each contain one or more pseudovacuoles which give a reddish gleam in transmitted light 13 13. Trichomes occur singly Pelonema p. 271 Trichomes occur in bundles Peloploca p. 270 Note: Peloploca is described as "sheath not demonstrated." It is included here on the possibility that it is sheathed and because of the morphological similarity to Pelonema. 14. Trichomes 6 to 20 microns long; motile by means of peritrichous fiagella; rigid, multi- cellular, bacillary forms in which the stained cells are differentiated into a series of light and dark bands; end cells rounded; commonly form chains up to 200 microns long. Individual cells in a trichome may separate as discoid elements and may grow out into filaments; common in peat and cow dung Caryophanon p. 831 General morphology similar to that found in Caryophanon, but individual trichomes are shorter and usually composed of 4 cells or 4 cell -pairs; trichomes are chain-form- ing but non-motile; recorded from the oral cavity of man and domestic animals Simonsiella p. 833 Not as above 15 15. Long trichomes attached by a globular holdfast to the intestinal walls of some insects and millipeds; a single endospore may be produced in any or all cells of the trichome, and if so, it usually lies in an oblique position Arthromitus p. 835 Trichomes 1.5 to 22.0 microns long; found in the cytoplasm of the rhizopod Pelomyxa palustris, generally aggregated close to the nucleus Cladothrix p. 930 Not as above 16 16. Entire trichomes unattached and actively motile by a gliding action on a solid surface; no flagella 17 Trichomes attached or free; non -motile; abstricted cells may be motile with a gliding action on solid surfaces 19 Note: References have been made in the literature to the multicellular nature of many small cells previously regarded as unicellular. They are mostly cells not more than 6 microns long and will be found by other characteristics to belong to genera located in Section F et seq. 17. Organisms oxidize hydrogen sulfide, depositing sulfur inside the cell Beggiatoa p. 838 Not as above 18 18. Trichomes composed of cells which are not clearly articulated at the junctions; com- plete trichomes very flexible Vitreoscilla p. 845 Trichomes composed of rod-like elements with little individual flexibility; bending occurs freely at the junctions Bactoscilla p. 848 19. Colorless trichomes; attached; cells are abstricted from the terminal position and are motile by a gliding action on a solid surface. Sulfur is not deposited internally Leucothrix p. 850 Colorless trichomes; arranged in bundles; non -motile; each cell in the trichome con- tains one or more gas vacuoles which gleam reddish in transmitted light Peloploca p. 270 Cells deposit sulfur internally Thiothrix p. 842 Note: Thiothrix is inserted here although classical descriptions of the genus indicate a sheath.
