cernible, the spores being imbedded in the slime holding the mass together. Usually single, though two or three fruiting bodies may become joined to form an irregular mass; each is attached to the substrate, however, and never bud one from another. Microcysts : Spherical, with thick outer wall or membrane. Highly refractile. 2.0 mi- crons in diameter, seldom larger. Vegetative colony: Characteristics vary with the substrate. On plain 1.5 per cent agar (no nutrients added): Very thin and transparent, often hardly visible except by transmitted light. Little or no pigmentation. Surface covered with fine, more or less regularly spaced ridges causing a dull macroscopic appear- ance without gloss or sheen. Margin very thin and quite regular. On rabbit dung decoction agar: Colony thicker, the surface being broken by veins or ridges radiating from the center. Thick central area often smooth and glossy while margin much the same as that on plain agar. Veins or ridges extend outward from center in loose spiral, always in clock-wise direc- tion. Pigmentation, yellow to pale orange, confined to thicker central portion, extends part way along veins to margin. On nutrient agar: Growth poor. Colony thick, at first heavily veined, the veins later merging to form an irregular glossy surface. Colony remains small, pigmentation usu- ally fairly heavy; margin thick, irregular to lobate. Physiology: Grows well on mineral salt- agar to which has been added dulcitol, inu- lin, cellulose, reprecipitated cellulose or starch; hydrolyzes starch; does not destroy cellulose to any appreciable extent. Best growth on suspension of killed bacterial cells in agar; suspended cells in growth area lysed. Development completely inhibited by arabinose, largely by maltose and man- nose. Source: Isolated from dried cow dung, Ames, Iowa. Habitat: Decomposed bacterial cells in dung. Illustrations: Beebe (ibid., Figs. 1-28). sti.pi.ta'tus. L. noun stipes, stipitis trunk, stalk; M.L. adj. stipitatus stalked. Vegetative cells: Rods 0.5 to 0.7 by 2.0 to 7.0 microns or longer. Grows well on nu- trient agar but does not fruit readily. Fruiting body: Nearly spherical, 175 mi- crons in diameter, deliquescent, sessile on a well developed, compact stalk, white to yellowish and flesh-colored. Microcysts 0.8 to 1.2 by 1.0 to 1.15 microns. Stalk 100 to 200 microns long, 30 to 50 microns wide. Source: Isolated from dung in laboratory cultures at Cambridge, Mass., Maine and Tennessee. Habitat: Found on decaying organic mat- ter in soil and in the dung of various ani- mals. Common in Polish soils, according to Krzemieniewski (Acta Soc. Bot. Poloniae, 5, 1927). Illustrations: Thaxter {op. cit., PI. 31, Figs. 30-33) and Krzemieniewski (op. cit., 4, 1926, PI. II, Figs. 13-14). 6. Myxococcus ovalisporus Krzemie- niewska and Krzemieniewski, 1926. (Acta Soc. Bot. Poloniae, 4, 1926, 15.) o.va.li'spo.rus. L. noun ovum egg; M.L. adj. ovalis oval; Gr. noun spora seed; M.L. noun spora a spore; M.L. adj. ovalisporus oval-spored. Vegetative cells: Not described. Fruiting bodies; Nearly spherical, charac- teristically shortened, ellipsoidal spore masses of light milky yellow color; these are often raised on a poorly developed stalk. This stalk always shows some bacterial cells remaining and, with respect to this and to color, is differentiated from M. stipitatus. From the base of the stalk or directly from the substrate, one or more small fruiting bodies develop. Microcysts are ellipsoidal, sometimes irregularly spherical, 1.0 to 1.4 by 1.3 to 1.9 microns. In culture it retains its differences from M. stipitatus. The latter sporulates best at room temperature, but M. ovalisporus sporulates best in an incu- bator (presumably at 37° C). Source: From soil from Poland. Habitat: Found on decaying organic mat- ter in soil. 5. Myxococcus stipitatus Thaxter, 1897. (Bot. Gaz., 23, 1897, 395.) Addendum: Species incertae sedis. As it stands now, the taxonomy of the genus
