The specific name selected for this peculiar form has once before done service, but apparently for something quite dissimilar. Schumacher, _Enum. Pl. Saell._ II., p. 199, has _P. luteo-album_. Fries thinks he had a perichaena on hand; at any rate, not a physarum, and makes Schumacher's combination a synonym for _Perichaena quercina_ Fr., which Rostafinski in turn makes synonymous with _P. corticalis_ (Batsch) R. If "once a synonym always a synonym" be esteemed good taxonomic law, this species must one day have another name. The present author, unwilling to change his colleague's preference in this case, nevertheless begs to suggest that such a binomial as _P. listeri_ would probably at once make future history of the species less eventful, and honor the memory of England's latest and most distinguished student of the group he loved. 28. PHYSARUM NUCLEATUM _Rex._ 1891. _Physarum nucleatum_ Rex., _Proc. Phil. Acad._, p. 389. Sporangia gregarious, spherical, 1/2 mm., white, stipitate; peridial wall membranaceous, rupturing irregularly, thickly studded with rounded white lime-granules; stipe about 1 mm., subulate, yellowish-white, rugose; columella none, capillitium dense, snow-white, with minute, white, round or rounded nodes, in the centre a conspicuous mass of lime forming a shining ball, not part of the stipe although sometimes produced toward it; spore-mass black; spores brown-violet, delicately spinulose, 6-7 mu. This species most nearly resembles in appearance and habit of growth _P. globuliferum_ Pers., but may be distinguished from it by the absence of a columella, by the central ball of lime, and the very small rounded lime-granules in the meshes of the capillitium. Exceptionally the lime granules of the sporangium wall are sparse or absent entirely, in which case the wall has a silvery or coppery metallic lustre. Pennsylvania, Nicaragua. 29. PHYSARUM WINGATENSE _nom. nov._ PLATE XVI., Figs. 3, and 9. 1876. _Tilmadoche columbina_ (Berk. & C.) Rost., _Mon., App._, p. 13 (?). 1889. _Tilmadoche compacta_ Wing., _Proc. Acad. Nat. Sci._, p. 48. 1894. _Physarum compactum_ List., _Mycetozoa_, p. 45. 1896. _Physarum compactum_ (Wing.) Morg., _Jour. Cin. Soc._, p. 91. 1899. _Tilmadoche compacta_ Wing., Macbr., _N. A. S._, p. 61. 1916. _Physarum columbinum_ (Rost.) Sturg., _Mycologia_, Vol. VIII., p. 4. Sporangia gregarious, or somewhat crowded, erect or cernuous, stipitate, gray or brownish gray, globose; peridium thin, metallic brown or bronze in color, splitting at maturity in floriform manner into six to twelve segments; stipe white or yellowish white, often shading to black or fuscous below, rather long, tapering upward; hypothallus none; columella none; capillitium extremely delicate, white or colorless, radiating from a central lime-mass or nucleus, and with ordinary nodules small and few, fusiform; spore-mass brown; spores by transmitted light, violet-brown, delicately warted, 7-8 mu.