microcysts. Definite fruiting bodies are produced in three of the genera. In Sporocytophaga the microcysts are produced from the vegetative cells without development of fruiting bodies. Key to the genera of family Myxococcaceae. I. Definite fruiting bodies formed. A. Microcysts not enclosed in larger cysts. 1. Fruiting bodies deliquescent. Genus I. Myxococcus, p. 883. 2. Fruiting bodies firm, not deliquescent. Genus II. Chondrococcus, p. 886. B. Microcysts enclosed in larger cysts. Genus III. Angiococcus, p. 889. II. No definite fruiting bodies formed. Genus IV. Sporocytophaga, p. 890. Genus I. Myxococcus Thaxter, 1892. (Bot. Gaz., 17, 1892, 403.) My.x.o.coc'cus. Gr. noun myxa mucus, slime; Gr. noun coccus berry; M.L. mas.n. Myxo- coccus slime coccus. Spherical spores in spherical or occasionally ellipsoidal upright fruiting bodies united by slime. The type species is Myxococcus fulvus (Cohn emend. Schroeter) Jahn. Key to the species of genus Myxococcus. I. Stalk lacking or indicated only by a constriction. A. Spores average less than 1.4 microns in diameter. 1. Fruiting body red or brownish flesh color. 1. Myxococcus fulvus. 2. Fruiting body light blood-red. 2. Myxococcus cruentus. B. Spores average 2.0 microns in diameter. 1. Fruiting body yellow to greenish yellow. 3. Myxococcus virescens. 2. Fruiting body yellow-orange to orange. 4. Myxococcus xanthus. II. Well developed stalk supporting spherical spore mass above. A. Spores spherical. 5. Myxococcus stipitatus. B. Spores ellipsoidal. 6. Myxococcus ovalisporus. 1. Myxococcus fulvus (Cohn, 1875, ful'vus. L. ad], fulvus reddish yellow. emend. Schroeter, 1886) Jahn, 1924. {Micro- Vegetative cells: Slender rods irregularly coccus fulvus Cohn?, Beitrage z. Biologie d. curved, 0.4 by 3.0 to 7.0 microns. Masses Pflanzen, 1, Heft 3, 1875, 181; Micrococcus are light flesh-colored. fulvus Schroeter char, emend., in Cohn, Fruiting bodies: Spherical or elongate, Kryptogamenflora v. Schlesien, S, 1, 1886, pear-shaped, constricted below, often with 144; Jahn, Beitrage zur bot. Protistologie. definite slimy stalk, flesh-red to brownish I, Die Polyangiden, Geb. Borntraeger, Leip- red; when dry, rust-red to brown, about 300 zig, 1924, 84.) microns in diameter. Spores 1.0 to 1.2 mi-
