Sporangia gregarious, sub-globose, sessile or plasmodiocarpous, smooth white or pallid, terete or somewhat compressed; peridium double, the outer wall calcareous, free and deciduous above, recurved and persistent below; the inner, smooth, pale purplish, more persistent; dehiscence more or less irregular beginning at the top; capillitium of large white nodules connected by short hyaline threads; spores generally spinulose, violaceous brown, 9-10 mu. As suggested by the author of this species it is properly a variety of _P. sinuosum_; certainly is, as it presents itself in this part of the world. Of the species last named we have compressed forms opening by narrow fissure along their knife-edged summit, with scarce place for capillitium at all between the approaching walls; again we have colonies of sporangia quite terete, calcareous without, opening in fragmental fashion at the top, displaying sometimes the thin membranous inner wall but at length fissured and gaping as in the more usual phase figured by authors, where the plasmodiocarp is simply compressed but not extravagantly thin. Both types occur in the western mountains, forms with and without calcium, fissured by wider or narrower cleft, _from the same plasmodium_; forms bilabiate and forms opening at first to display an inner peridium; forms globose with narrow base, but apex cleft, and forms ellipsoidal, yet compressed, opening like the gaping of some tiniest bivalve; did not Persoon say _P. bivalve_! all are bivalvular at the last! Nay; but what are these? Here are some of the shorter forms become suddenly obovate, and are actually mounted on _stipes_! Surely variation in the same plasmodium can no farther go![22] Not rare. Colorado to the Pacific Coast. Evidently a western-American variation of Bulliard's European type. The latter occurs abundantly in Iowa on the shores of Lake Okoboji; otherwise not common. 6. PHYSARUM BOGORIENSE _Racib._ 1898. _Physarum bogoriense_ Raciborski, Hedw., XXXVII., p. 52. Sporangia sessile, elongate, creeping but not reticulate, semicircular in transverse section, sometimes globose or depressed globose; peridium double, the outer thick coriaceous, yellow or brown, dehiscing stellately into persistent more or less triangular reflected lobes, remote from the thin, colorless inner wall; columella none; capillitium feebly developed, the nodes white, large, isodiametric; spores bright violet, smooth, 7-8 mu. This species is not uncommon in the mountains of Colorado where it has been taken at various stations by Bethel. It is reported from Pennsylvania and South Carolina. Raciborski describes it from Java. In habit it is very much like some forms of _P. sinuosum_ but differs in the depressed, rather than compressed sporangia, and in the brown color of the outer peridium. 7. PHYSARUM ALPINUM _G. List._ 1910. _Physarum alpinum_ G. Lister, _Jour. Bot._, XLVII, p. 73.