So.ran'gi.um. Gr. noun sorus a heap; M.L. noun sorus a fungus spore pustule; Gr. noun angium a vessel; M.L. noun Sorangium heaped vessel. Description as for the family. The cysts are united into rounded fruiting bodies. Eight species have been allocated to this genus. The type species is Sorangium schroeieri Jahn. Key to the species of genus Sorangium. I. Fruiting bodies not black when ripe. A. Primary cysts absent; fruiting body shows only angular, spherical or ellipsoidal small cysts. 1. Cysts angular. a. Fruiting body very small (50 to 80 microns), often irregularly cerebriform; the angular cysts often completely separated from each other and about 13 microns in diameter. 1. Sorangium schroeteri. aa. Fruiting body composed of many small cysts. b. Cysts orange-red in color; over 5.0 microns in diameter. 2. Sorangium sorediatum. bb. Rusty brown color; cysts less than 3.5 microns in diameter. 3. Sorangium cellulosum. 2. Cysts spherical or ellipsoidal. 4. Sorangium spumosum. B. Both primary and secondary cysts present. 1. Primary cysts small and numerous, about 20 microns, with definite membrane and few angular secondary cysts. 5. Sorangium septatum. 2. Primary cysts large, with delicate, often indefinite, membrane. 6. Sorangium compositum. II. Fruiting bodies black or brownish-black when ripe. A. Primary cysts generally not formed. 7. Sorangium nigrum. B. Primary cysts generally formed. 8. Sorangium nigrescens. 1. Sorangium schroeteri Jahn, 1924. regularly into well delimited portions, many (Beitrage zur bot. Protistologie. I, Die angled, usually about 12 microns in diame- Polyangiden. Geb. Borntraeger, Leipzig, ter, and in other places into areas less well 1924, 73; regarded as a synonym of Soran- delimited and about 14 microns in diameter. gium compositum by Krzemieniewski, Acta Resembles gelatin which has dried in a sheet Soc. Bot. Poloniae, 5, 1927, 96.) and cracked into regular areas. Rods in schroe'te.ri. M.L. gen. noun schroeteri of cj^sts 5 microns long. Cysts sometimes occur Schroeter; named for Julius Schroeter. together in large numbers, covering an area Vegetative cells: Not described. to 0.5 mm. Fruiting bodies: Very small, circular, Source: Found by Jahn (op. a<., 1924, 73) swollen, often kidney-shaped with brain- five times on rabbit dung in the environs of like convolutions, usually 60 microns (oc- Berlin. casionally 120 microns) in diameter, bright Illustrations: Jahn (ibid., PI. 2, Fig. 22). orange-red. Surrounded by a delicate .slime membrane about 0.7 micron thick, apparent 2. Sorangium sorediatum (Thaxter, only with high magnifications. Divided 1904) Jahn, 1924. {Fohjangium sorediatum secondarily into angular cysts by sutures Thaxter, Bot. Gaz., 37, 1904, 414; Jahn, extending inward which divide the mass Beitrage zur bot. Protistologie. I, Die
