Sporangia gyrose, variable in form, or plasmodiocarpous and irregular, venulose, sessile upon a common, strongly developed hypothallus, sometimes isolated and irregularly globose, dehiscing irregularly or by longitudinal fissure, yellowish or greyish white; columella none; capillitium delicate, the nodules elongate, variable in size; spores pale violaceous, minutely spinulose, 7–10 µ.

This is a European species recently resuscitated by Dr. Jahn. It perhaps might more correctly be recorded as P. gyrosum Jahn, since Rostafinski certainly attempted in his description to cover two apparently distinct things. He seems to have had before him Fuligo muscorum Schw. and "P. gyrosum," but he thought them the same, and his description touches now one, now the other. Since F. muscorum Schw. has all along held its own and received due recognition, it is interesting to note the recovery of this gyrose form.

Judging by description and figures, it resembles a very large, sessile phase of P. polycephalum. See further under that species.

Europe, Japan, Eastern United States (?).

54. Physarum polycephalum Schw.

[Plate VIII.], Figs. 2, 2 a, 2 b.

Sporangia spherical or irregular, impressed, gyrose-confluent, helvelloid, umbilicate below; peridium thin, ashy, covered with evanescent yellow squamules, fragile; stipe from an expanded membranaceous base, long-subulate, yellow; spores smooth, violet, 9–11 µ.

A most singular species and well defined is this, occurring in masses of decaying leaves or on rotten logs. The plasmodium at first colorless; as it emerges for fructification, white, then yellow, spreading far over all adjacent objects, not sparing the leaves and flowers of living plants; at evening slime, spreading, streaming, changing; by morning fruit, a thousand stalked sporangia with their strangely convoluted sculpture. The evening winds again bear off the sooty spores, and naught remains but twisted yellow stems crowned with a pencil of tufted silken hairs. August.