This species is well marked by several characteristics; the brilliant wall of the peridium, white-flecked and laciniate, the delicate _Didymium_-like capillitium running from centre to peridium, and especially the peculiar aggregation of lime at the center of the sporangium, like nothing else except a similar structure found in _Physarum nucleatum_ Rex. The variations affect the stipe and the distribution of the capillitial lime. Some eastern specimens show stipes melanopodous, black below; specimens from Ohio and Nicaragua show stipes milk-white throughout. As to the capillitium, in some of the Nicaragua collections the lime is more uniformly distributed through the capillitium, and accordingly the nucleus is not conspicuous, its place being taken by two or three nodes plainly larger than the others. The peculiar brown metallic lustre of the peridial wall, and the strongly developed calcareous patches with which the peridium is covered are constant features. That this is the _Didymium columbinum_ Berk., or _T. columbina_ (Berk.) Rost., is very doubtful; the specific name given by Wingate becomes inapplicable when the series is transferred to _Physarum_, since in that genus the combination is already a synonym. See _P. compactum_ Ehrenberg, _Syl. Myc. Berl._, p. 21 (1818), cited repeatedly in the synonymy; Fries, _op. cit._, Vol. III., p. 101. So also _P. columbinum, l. c._, pp. 133, 135, etc., to say nothing of the fate of Persoon's first record, _Obs. Mycol. pars prim._, p. 5, 1796. This is Wingate's species, let it bear his name. 30. PHYSARUM NEWTONI _Macbr._ PLATE XIV., Figs. 5, 5 _a_, 5 _b_. 1893. _Physarum newtoni_ Macbr., _Bull. Lab. Nat. Hist. Iowa_, II., p. 390. 1899. _Physarum newtoni_ Macbr., _N. A. S._, p. 37. 1911. _Physarum newtoni_ Macbr., Lister, _Mycetozoa, 2nd ed._, p. 54. Sporangia simple, gregarious, short-stipitate or sessile, globulose or flattened, when not globose, depressed and deeply umbilicate above, purple, smooth, thin-walled, stipe when present very short and concolorous; columella none; hypothallus none; capillitium abundant, delicate, with more or less well-developed nodules, which are also concolorous; spores by transmitted light, dark brown, thick-walled, rough, nucleated, about 10 mu. A very handsome little species collected by Professor G. W. Newton in Colorado, at an altitude of several thousand feet. Easily recognized by its almost sessile, rose purple, generally umbilicate sporangium. 31. PHYSARUM PSITTACINUM _Ditm._ 1817. _Physarum psittacinum_ Ditm., Sturm, _Deutsch. Fl. Pilze_, p. 125. 1829. _Physarum psittacinum_ Ditm., Fries, _Syst. Myc._, III., p. 134. 1873. _Physarum psittacinum_ Ditm., Rost., _Mon._, p. 104. 1911. _Physarum psittacinum_ Ditm., Lister, _Mycetozoa, 2nd ed._, p. 55.