24. Curved and irregular cells; may branch in young cultures; capable of using phenolic compounds as the sole source of carbon; gas, presumably nitrogen, produced in 0.1 per cent nitrate broth but no nitrites are produced; no acid from carbohydrates Mycoplana p. 304 Not as above 25 25. Curved rods, very small, about 1.0 micron in length, which, during growth, produce closed rings, 2.0 to 3.0 microns in diameter, which later change to two horseshoe- shaped halves fastened together without any evidence of divisional lines. These divide into separate rods which reproduce the cycle; encapsulated; grow well in 0.5 per cent peptone water Microcyclus p. 25S Not as above 26 26. Curved or S-shaped rods, 0.1 to 0.2 bj' 6 to 8 microns or longer; very poor growth on peptone agar; or short straight rods 0.5 by 1 to 2 microns; good growth on peptone agar; on inorganic thiosulfate agar, small watery colonies produced which turn white from the deposi- tion of sulfur; grow autotrophically, oxidizing thiosulfate to sulfur and sulfate Thiobacillus p. 83 Not as above 27 27. Curved cells, 1 by 5 to 10 microns, which form chains which may twist around each other to form coiled, non-septate, non-motile colorless bundles; enclosed in a spheri- cal, solid gelatinous mass from 10 to 17 microns in diameter; found floating on water containing decomposing plant material Myconostoc p. 260 Not as above 28 28. Curved organisms which grow on precipitated-cellulose mineral-salts agar producing a clearing of the medium around the colonies; also grow in 0.5 per cent peptone water in which a strip of filter paper is half immersed, weakening the filter paper sufficiently for the fibers to separate on slight agitation or reducing it to a pulpy mass; organisms are arranged in palisade fashion similar to the corj^nebacteria Cellulomonas p. 601 (See also Vibrio agarliquefaciens and V. fuscus.) Not as above 29 29. Curved organisms which grow on a filter-paper mineral-salts medium oxidizing the cellulose to oxycellulose 30 Not as above 31 30. Sickle-shaped; cells no longer than 2.0 microns; stain more intensely at the center than at the ends; no growth on a mineral salts agar containing starch; green, cream or brownish on filter paper Cellfalcicula p. 252 Curved cells 1.5 to 5.0 microns in length, with rounded ends; grow moderately well on mineral salts agar containing starch; cream, brown or no pigment on filter paper Cellvibrio p. 250 31. Curved rods which transform completely into coccoid forms during growth of the colony. Rods elongate and divide. At the point of division the rods grow out at an angle to the original axis and divide again at the angle when the cell has doubled its length. This process continues until a colony is formed. Ultimately the rods trans- form completely into cocci Arthrobacter p. 605 Note: The emphasis lies on the final transformation into cocci. Some authori- ties may consider that limited true branching may occur. If this is admitted, the dividing line between Arthrobacter and Nocardia becomes very slim. The author's observations of Arthrobacter globiforme fit the above statement, and it is suggested that these criteria be adopted, true branching forms which later disintegrate being assigned to Nocardia. Not as above 32
