6. ARCYRIA COOKEI, Mass. Sporangium ovoid-cylindric, the calyculus very small. Stipe long, erect, gray to mouse-color, darker below, arising from a thin hypothallus. Capillitium not much expanded after dehiscence, ovoid-cylindric, erect, gray to mouse-color; the superficial threads densely and uniformly covered with minute warts, 3-5 mic. in thickness; the threads of the interior thinner, about 2 mic. and smooth, or with very minute scattered warts. Spores globose, even, 6-8 mic. in diameter. See Plate I, Fig. 16. Growing on old wood, mosses, etc. Capillitium 1-2 mm. long, the stipe about the same length. It seems as common as _Arcyria cinerea_, and has heretofore been included in it. See Massee's Monograph, p. 154. 7. ARCYRIA DIGITATA, Schw. Sporangium cylindric, the calyculus very small. Stipe long, ascending, brownish in color, usually several fasciculate or to some extent connate, the sporangia divergent at the apex. Capillitium not much expanded after dehiscence, cylindric, pale cinereous, or pale yellowish; the threads variable in thickness. 2-4 mic., those at the surface densely and minutely warted, those of the interior nearly smooth. Spores globose, even, 6-8 mic. in diameter. Growing on old wood. Capillitium 2-4 mm. long, the stipe about the same length. _Arcyria bicolor_, B. & C. III. HETEROTRICHIA, Massee. Sporangia regular, oblong-ovoid, stipitate; the wall a thin delicate membrane, the upper part disappearing at maturity, leaving the basal portion as a small calyculus. Stipe filled with large thick-walled vesicles, which are sub-angular from mutual pressure; these become smaller upward, and pass gradually into normal spores. Capillitium issuing from the interior of the stipe, the central and superficial threads dissimilar, forming a complicated network, with numerous free extremities, the surface minutely warted, or with annular ridges. Spores globose, brownish. Distinguished from Arcyria by the numerous free extremities of the peripheral portion of the network. 1. HETEROTRICHIA GABRIELLÆ, Massee. Sporangium oblong-ovoid, stipitate; the calyculus small, thin, smooth. Stipe very short, erect, yellowish-brown in color. Capillitium much elongated after dehiscence, cylindric-ovoid, sub-erect; the threads of the central portion about 1.5 mic. thick, with slightly elevated ridges partly encircling the tube, nearly colorless; threads of the peripheral portion bright yellow, 5-6 mic. thick, with numerous short acute free branches, the surface densely and minutely warted. Spores in mass, yellowish-brown, globose, even, 7-8 mic. in diameter. See Plate I, Fig. 18. Growing on wood; S. Carolina, _H. W. Ravenel_. The sporangia densely crowded, becoming scattered toward the margin of the cluster. Massee's Monograph of the Myxogasters. ORDER V. TRICHIACEÆ.