18. Physarum confertum Macbr. nom. nov.
[Plate XV.], Figs. 1, 1 a, 1 b.
- 1899. Physarum atrum Schw., Macbr., N. A. S., p. 36.
- 1911. Physarum atrum Schw., Lister, Mycetozoa, 2nd ed., p. 74.
Sporangia small about .2–.3 mm. in diameter, gregarious, confluent, clustered or heaped, dull violaceous brown; peridium thin, more or less transparent, generally limeless but sometimes lightly sprinkled with minute white flecks: capillitium scanty, the calcareous nodes small, rounded, elongate, white! columella none; spores violet-brown, distinctly warted, 10–12 µ.
Having been assured on information believed trustworthy that the Schweinitzian herbarium confirmed the identity of the species before us, in the first edition of this work the form was listed as P. atrum Schw. Meantime in the herbarium referred to, at Philadelphia the original type of P. atrum still exists. My valued correspondent, Mr. Hugo Bilgram, has recently given it careful study. It is a limeless P. didermoides (Pers.) R.! Small wonder we have had trouble! Exit Physarum atrum Schw.
The species is not uncommon, especially eastward; has been generally ignored for reasons cited.
Distinguished from everything else by the color and small size of the heaped sporangia. It resembles some phase of P. virescens where the sporangia are small and somewhat heaped or rather aggregated, and scantily supplied with lime; but in such case the lime is yellow and the spores are small.
This species has also been constantly referred to our confused P. cinereum, P. plumbeum, etc., but Schweinitz, who certainly had seen P. cinereum in Europe, since he cites it, under several forms, in the Conspectus, found the species in America and proceeded in Pennsylvania in December to find something else, very different as he thought, and in fact. He called this new discovery P. atrum, "beautifully reticulate", he says "like P. cinereum but larger."
Most American students in an effort to keep faith with their pioneer mycologist, have taken cue from the specific name, looking for something black, heedless that in Pennsylvania almost any delicate thing has 'dark looks' in the middle of the winter! Berlese in Saccardo Syll. VII., p. 350, regarding P. atrum as a synonym, writes for the black American specimens, P. reticulatum, emphasizing another Schweinitzian descriptive adjective. But P. atrum Schw. has had place in literature to this hour.
19. Physarum melleum (Berk. & Br.) Mass.