Æthalia solitary or sometimes two or three together, large 2–4 cm. in diameter, spherical or spheroidal, purplish-gray or brown, smooth, shining; the peridium thick, simple but in microscopic section showing two or three successive layers; capillitium of abundantly branching, irregular, transparent tubules, marked by numberless warts and transverse rings or wrinkles, spores in mass yellowish gray, by transmitted light, colorless, smooth or only faintly reticulate or roughened, 5–6 µ.

This, one of the largest and most striking of the slime-moulds, is by students generally mistaken for a puff-ball. It occurs on stumps and rotten logs of various sorts in the Mississippi valley, more often affecting stumps of Acer saccharinum L. The fructification, when solitary, about the size of a walnut, though sometimes larger; when clustered, the individuals are smaller. The form depends largely upon the place in which the fruit is formed. The plasmodic mass is so large that its form is determined by gravity. Thus on the lower surface of a log raised a little distance from the earth the æthalium is often pyriform. This fact did not escape Micheli. See Nov. Plant. Gen., Tab. 95. The plasmodium is pale pink, soon becomes buff when exposed in fruiting, finally pallid or somewhat livid, and is outwardly changed into the stout, tough peridium. This consists of an intricate network of irregular gelatinous tubules enclosing within the meshes protoplasmic masses of pretty uniform size, 60–100 µ. Outwardly the protoplasmic vesicles predominate; inwardly the gelatinous tubules, which are, in some instances at least, continued toward the centre of fructification to form the capillitium. The protoplasmic masses referred to respond to ordinary stains, are often broken into numberless small cells corresponding in size and appearance to ordinary spores.

Not common. New England, Ohio, Iowa. Perhaps more abundant in the Mississippi valley; Canada.

3. Lycogala exiguum Morg.

Æthalia small, 2–5 mm. in diameter, gregarious, globose, dark brown or black, sessile, minutely scaly, irregularly dehiscent; the peridium thin, the vesicles comparatively few, in irregular patches which are more or less confluent; capillitium as in preceding species, the tubules slender and branching; spore-mass pale, ochraceous, spores by transmitted light colorless, almost smooth, 5–6 µ.

Found in the same situations as No. 1, and at the same season. Recognizable by its gregarious habit, not crowded nor superimposed, small size, and dusky color. The little spheres occur a dozen or more in a place, dark lead-colored, shading to black, opening rather regularly at the top. It looks like a depauperate L. epidendrum, but seems to be constantly collected.

Our specimens are from Ohio, Iowa, Missouri, Canada.