Æthalium pulvinate, 2–8 cm. broad, at first silvery white, later less lustrous, the cortex irregularly and slowly deciduous; hypothallus at first conspicuous as a white margin extending round the entire aethalium, evanescent without, but persisting as a firm membrane beneath the spore-mass, pseudo-capillitium abundant, tending to form erect central masses which persist long after the greater part of the fruit has been scattered by the winds; spore-mass umber, spores by transmitted light pale, reticulate over about two-thirds of the surface, the remainder slightly warted, 8–9 µ.

Not common. Often confused with the following, the spores of the two forms being very much alike; the internal structure, entirely different, and once compared, the two are thereafter easily distinguished at sight by external characters. The sporangial make-up is indifferent, confused. It represents a phase in development whence might issue columellæ with capillitium-branches or distinct tubular sporangia with persisting walls; or are such structures here but reminiscent only? Compare Amaurochaete atra, where similar conditions prevail. There differentiation goes on to the formation of a structure of which Stemonitis is type; here the sporangium-wall becomes dominant; suffers modification for spore-disposal, an idea reaching fair expression in Cribraria and Dictydium.

The plasmodium is white, noted Bulliard. Fries cites with approval the words of Schweinitz,—"color corticis ab initio argenteus sericeo nitore insignis; sed deinde sordescit e griseo in subfuscum vergens." Sometimes the surface does indeed shine as silver!

The fructification appears to be isolated in each case; the entire plasmodium consumed in a single plasmodiocarp.

Widely distributed. Maine to California, and south.

2. Enteridium Ehrenberg

Fructification æthalioid; the confluent sporangia inextricably interwoven, the walls perforate by large openings, the resultant network of broad plates and bands widening at the points of intersection.

The genus Enteridium is distinguished from Reticularia chiefly by the more perfectly developed sporangial walls. These are everywhere membranous and do not show the abundant filiform dissipation so characteristic of Reticularia. The resultant structure in Reticularia is a mass of more or less lengthened and anastomosing threads; in Enteridium, an exceedingly delicate but sufficiently persistent sponge. The "net-like, three-winged skeleton" referred to by Rostafinski results from the union at one point of three adjoining sporangia. Compare the section of the adjoining cells of a honeycomb.