1. Cysts rounded to spherical. a. Ripe cysts yellow, reddish j^ellow, orange or light red; not brown, b. Cj-sts several or numerous and small. c. Not closely appressed. d. Slime envelope transparent white or colorless. e. Usuallj^ 10 to 15 cysts. Rods in cysts, 3 microns long. Cysts 75 to 200 microns. 1. Polyangiuni vitellinum. ee. Cj'-sts numerous. Rods 1.3 to 2.0 microns long. Cysts 20 to 80 microns. 2. Polyangiuni minus. dd. Slime envelope bright yellow. 3. Polyangiuni lideuni. cc. Closely appressed; often polygonal due to pressure. d. Bright yellow. 4. Polyangiuni morula. dd. Orange. 5. Polyangiuni cellulosum. bb. Cysts single, large. c. Large, 250 to 400 microns; reddish yellow. 6. Polyangium. simplex. cc. Smaller, 30 to 60 by 50 to 130 microns; orange to light red. 7. Polyangium ochraceum. aa. Ripe cysts reddish brown to dark brown. b. Cysts lying free, covered by a more or less definite slime envelope, c. About 60 microns in diameter; slime envelope delicate and colorless. 8. Polyangium jusmm. cc. About 35 microns in diameter; slime envelope yellow. 9. Polyangiuni aureuni. bb. Cysts rounded, in stellate arrangements on a slimy substrate. 10. Polyangium stellatum. 2. Cysts elongate, coiled. a. Cysts brownish red. 11 . Polyangium. ferrugineum. aa. Cysts bright orange-j^ellow. 12. Polyangium indivisum. B. Sorus white or gray in color. 1. Hyaline slime envelope white, foamy in appearance; cysts average 28 by 34 microns. 13. Polyangium spumosuni. 2. Sorus flat, crust-like, smoke-gray in color due to slime envelope; cysts average 36 by 44 microns. 14. Polyangiuni fumosum. II. Aquatic, parasitic on Cladovhora. 15. Polyangium parasiticum. 1. Polyangium vitellinum Link, 1809. cysts, milky white. Rods large, cylindrical, (Link, Mag. d. Ges. Naturforschender rounded at either end, 0.7 to 0.9 by 4.0 to Feunde zu Berlin, 3, 1809, 42; Myxobacter 7.0 microns. aureus Thaxter, Bot. Gaz., 17, 1892, 403.) Fruiting body: Cysts golden yellow, usu- vi.tel.li'num. L. noun vitellus an egg ally relatively spherical, 75 to 150 microns, yolk; M.L. adj. vitellinus like egg yolk. occasionally 200 microns in diameter, al- Vegetative cells: When rising to form most always surrounded by a white, slimy
