1791. _Trichia cinerea_ Bull., _Champ. de France_, p. 120, Tab. 477, Fig. iii. 1801. _Arcyria cinerea_ (Bull.) Pers., _Syn. Fung._, p. 184. Sporangia scattered or gregarious, ovoid or cylindrical, generally tapering upward, about 2-3 mm. high, ashen gray, sometimes with a yellowish tinge, stipitate; calyculus very small, thin; stipe about half the total height, rising from a small hypothallus, thin, gray or blackish, densely crowded with spore-like cells; capillitium dense, freely branching, ashen, or yellowish, little wider below, minutely spinulose; spore-mass concolorous, spores by transmitted light colorless, smooth, 6-7 mu. A very common little species, easily recognized by its color and habit. The capillitium is more dense than in any other species and expands less. The stipe is about equal to the expanded capillitium, unusually long. The plasmodium occurs in rotten wood, especially species of _Tilia_, is gray and, judging from the number of sporangia found in one place, scanty. Bulliard, _l. c._, gives the first account of the species by which it can with any certainty be identified. By some authors _Clathrus recutitus_ Linn. is cited as a synonym. We fail to distinguish _A. cookei_ Mass. from the old type. Widely distributed; Maine to Alaska, and south to Mexico and Nicaragua. 10. ARCYRIA DIGITATA (_Schw._) _Rost._ 1831. _Stemonitis digitata_ Schw., _N. A. F._, p. 260, No. 2350. 1868. _Arcyria bicolor_ Berk. & C., _Jour. Linn. Soc._, X., p. 349. 1875. _Arcyria digitata_ (Schw.) Rost., _Mon._, p. 274. Sporangia compound, that is gathered in tufts, number 3-12 or more on a single stipe, the clusters themselves scattered; individual sporangia elongate cylindric, about 3-4 mm. long, ashen gray or nearly white, stipitate; stipe as long or longer than the sporangium, stout, sometimes showing traces of consolidation of several, sometimes none, dark brown or black; capillitium looser and more expanded than in the last, the threads more strongly spinulose; spore-mass concolorous, spores under the lens colorless, smooth, globose, 7.5-8 mu Closely related to the preceding, but different in habit and on the whole larger and more robust throughout. The stipes in some cases are completely merged in one; in others traces of coalescence remain. The number of united sporangia varies. There are some clusters before us containing 16 and 18 in a single fascicle! Not very common. On rotten wood of deciduous trees, especially south. New England, Pennsylvania, Ohio; Black Hills, South Dakota, and south to Nicaragua. _Arcyria bicolor_ Berk. & C. seems to refer to the fact that the sporangia have sometimes an ochraceous tint. Berkeley's specimens are from Cuba. Our latest specimens are from Nicaragua; the form seems not to be reported from the old world. 11. ARCYRIA POMIFORMIS (_Leers_) _Rost._ 1775. _Mucor pomiformis_ Leers, _Flor. Herb._, p. 218. 1875. _Arcyria pomiformis_ Rost., _Mon._, p. 271.