This species is instantly distinguishable from all cognate forms by its peculiar sooty color. Not less is the species structurally marked by its capillitium. The latter below is exactly as in the species of _Tilmadoche_. Indeed, the present species unites characters supposed to distinguish _Physarum_ from _Tilmadoche_, and would so far justify those authors who bring all the species of both genera together under one generic name. In any case the species is by its capillitium entirely distinct from _P. galbeum_, as well as by the structure of the stipe and the peridial surface. The plasmodium, at first watery, emerges from decayed elm logs and soon takes on a peculiar greenish tint preserved somewhat in the mature fruit. Rostafinski, _Monograph_, pp. 105, 106, rejects Berkeley's specific name, _flavicomum_, because it refers to the somewhat indefinite, characteristic color. As this is no valid reason for change, we have restored Berkeley's specific name, which by general consent has priority. _N. A. F._, 3299. Not common. New Jersey, Ohio, South Carolina, Iowa. 52. PHYSARUM BETHELII (_Macbr._) _Lister_. 1899. _Tilmadoche bethelii_, Macbr., _Exempl. ad Herbaria._ 1911. _Physarum gyrosum_ Rost., List., _Mycetozoa, 2nd ed._, p. 75. Sporangia scattered, globose, umbilicate below, .5-1 mm. in diameter, iridescent blue, or sometimes tinged by the presence of delicate pale yellow calcareous scales, stipitate; stipe rather short, black or dark brown, equal; capillitium dense, radiating from the black, slightly intrusive summit of the stipe, and from the base of the peridium ascending; the nodules not numerous, elongate, branching betimes, pale yellow; spores minutely roughened, 10-12 mu. This beautiful delicately tinted little species is clearly tilmadochoid in the Friesian sense. The capillitium persists after the fall of the upper filmy peridium, adherent below to the persisting peridial base. Collected thus far twice only; by Professor Bethel and by Professor Sturgis, Colorado. SECTION 2 _=Tilmadoche= Fries_ 53. PHYSARUM GYROSUM (_Rost._) _Jahn._ 1875. _Physarum gyrosum_ Rost., _Mon._, p. 111. 1902. _Physarum gyrosum_ Rost., Jahn, _Ber. Deutsch. Bot. Ges._, XX., p. 272, t. XIII. 1911. _Physarum gyrosum_ Rost., List., _Mycetozoa, 2nd ed._, p. 75. Sporangia gyrose, variable in form, or plasmodiocarpous and irregular, venulose, sessile upon a common, strongly developed hypothallus, sometimes isolated and irregularly globose, dehiscing irregularly or by longitudinal fissure, yellowish or greyish white; columella none; capillitium delicate, the nodules elongate, variable in size; spores pale violaceous, minutely spinulose, 7-10 mu.