oooo Sporangia obovate, compound, clustered, the stipe fuscous, fluted, short. 41. _P. nicaraguense_ OOOO Sporangia yellow, rarely iridescent or brown. o Capillitial nodes white. x. Stipe also white 42. _P. sulphureum_ xx. Stipe flesh-colored, spores smaller 43. _P. carneum_ xxx. Stipe red or reddish brown 44. _P. citrinellum_ xxxx. Stipe yellowish, flaccid, sporangia leocarpine 45. _P. albescens_ xxxxx. Stipe very short or none, sporangia cylindric, brown 46. _P. variabile_ oo Capillitium nodes yellow or orange-yellow. x. Badhamioid, larger,--to .8 mm. 47. _P. auriscalpium_ xx. Physaroid, base persistent 48. _P. oblatum_ ooo Capillitium nodes pure yellow. x. Capillitial threads yellow 49. _P. galbeum_ xx. Capillitial threads hyaline 50. _P. tenerum_ xxx. Peridium iridescent. + Capillitium persistent 51. _P. flavicomum_ ++ Capillitium less persistent, larger 52. _P. bethelii_ SECTION II. TILMADOCHE I. Aethalioid, gyrose or irregular 53. _P. gyrosum_ II. Fructification stipitate. 1. Sporangia irregular, often convolute, involved 54. _P. polycephalum_ 2. Sporangia simple, nutant, discoidal. _a._ Thin-walled, grey or white. 55. _P. nutans_ _b._ Vari-colored, yellow, greenish, orange, etc. 56. _P. viride_ 1. PHYSARUM SERPULA _Morgan._ PLATE IX., Figs. 6, 6_a_, and 6_b_. 1831. _Physarum reticulatum_ Alb. & Schw., Schweinitz, _N. A. F._, No. 2295. 1885. _Physarum gyrosum_ (Rost.) Wingate, Ellis, _N. A. F._, No. 1396. 1892. _Physarum gyrosum_ Rost., Massee, _Mon._, p. 307. 1892. _Cienkowskia reticulata_ Rost, Macbr., _Bull. Nat. Hist. Iowa_, II., 2, p. 150. 1894. _Badhamia decipiens_ Berk., Lister, _Mycetozoa_, p. 33, in part. 1896. _Physarum serpula_ Morg., _Cin. Soc. Nat. Hist._, p. 101. 1899. _Physarum serpula_ Morg., Macbr., _N. A. S._, p. 29. 1911. _Physarum serpula_ Morg., Lister, _Mycetozoa, 2nd ed._, p. 81.