The shadowy little species has had an eventful history, dipping in and out of our story in most uncertain fashion. Beginning with Fries, as noted, it received confirmation at the hands of DeBary, and by Rostafinski was given priority over a long list of synonyms, and figured. The earlier English authors follow Rostafinski, but for Lister in the _Mycetozoa_, p. 51, the species becomes a synonym of _T. alba_ as _P. nutans_, the description appropriately enlarged to receive it. Meantime American students generally confused it with the tilmadoches on the one hand and _P. nefroideum_ R. (supposed) on the other. In 1897, Robt. Fries in _Sver. Myxom. Flora_, brings the species again to view as co-partner with _P. nutans_ and in the _Mycetozoa, 2nd ed._, p. 67, it appears as sub-species to the same.
The resemblance to _P. album_ or _P. nutans_, is chiefly as intimated, a matter of definition; real differences are found in the irregular capillitium, fitting a globose sporange, in the character of the stipe and the consequent pose. See under _P. nutans_ and _P. notabile_.
1881. _Physarum nodulosum_ Cke. & Balf., _Rav. N. A. F._, Exsic., 479. 1889. _Badhamia nodulosa_ Massee, _Jour. Myc._, Vol. V., p. 186. 1891. _Physarum calidris_ Lister, _Jour. Bot._, Vol. XXIX., p. 258. 1896. _Craterium nodulosum_ (Cke. & Balf.) Morg., _Jour. Cin. Soc._, p. 87. 1899. _Physarum nodulosum_ Cke. & Balf., Macbr., _N. A. S._, p. 51. 1911. _Physarum pusillum_ List., _Mycetozoa, 2nd ed._, p. 64.
Sporangia gregarious; minute, globose, bluish-white, the sporangial wall thin and more or less encrusted with lime, breaking up irregularly, stipitate; stipe slender, longer than the sporangium, attenuate upward or even, bright brown, rugose, expanded above into a shallow cup-like base for the sporangium; columella none; capillitium with lime-knots more or less abundant, white, often uniting, badhamioid; spore-mass black; spores by transmitted light, pale lilac-brown, almost smooth, 10-12 µ.
One of the smallest species of the genus, by its proportionally long stipe and small round sporangium reminding one somewhat of _P. globuliferum_; much smaller, however, and in every way different. The generic characters are mixed, and the species has been accordingly variously referred. The lower part of the peridium is sometimes persistent after the dehiscence, and so far reminds of _Craterium_. But this character is not constant, and even at best the persisting part is very small, not greater than in _P. melleum_, for example. On the other hand, the capillitium in some sporangia is strongly calcareous, reminds of _Badhamia_, but in most sporangia the _Physarum_ characters are sufficiently clear.