FAMILY V. MYXOCOCCACEAE 



885 



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 



