Growing on old wood, leaves, mosses, etc. Sporangium .4-.5 mm. in diameter, the stipe two or three times as long. The species is more particularly distinguished by its small spores. 5. DIDYMIUM MINUS, Lister. Sporangium depressed-globose, the base umbilicate, stipitate, rarely sessile and plasmodiocarp; the wall a dark-colored membrane with a thin layer of stellate crystals of lime, breaking up gradually and falling away. Stipe erect or sometimes bent at the apex, variable in length, rarely wanting, from pale brown to blackish in color, rising from a small hypothallus; the columella reaching the center, brown or blackish, rough, convex, subglobose or pulvinate, substipitate. Capillitium of slender colorless threads, radiating from the columella and more or less branched outwardly. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter. Plate XII, Fig. 39. Growing in vast abundance in Spring on old leaves, bark, wood, etc. Sporangium .4-.6 mm. in diameter, the stipe scarcely longer but usually shorter than the diameter of the sporangium rarely absent. It is considered by Lister to be a variety of _D. farinaceum_; it differs from this species in its smaller and less-depressed sporangium and in its smaller nearly smooth spores. _B. Sporangia sessile._ 6. DIDYMIUM EFFUSUM, Link. Sporangia gregarious or scattered, sessile on a flattened base, convex above, various in shape, subrotund or by confluence effused and venosely creeping; the wall very thin and pellucid, invested with a thin flocculose layer of minute crystals of lime. The columella hemispheric, rugulose, usually snow-white. Capillitium of very slender colorless threads, furnished with numerous minute protuberances, much branched and combined into a dense net. Spores globose, very minutely warted, dark violaceous, 10-11 mic. in diameter. Growing on old leaves, wood, etc. Sporangium about .5 mm. in diameter or thickness, sometimes confluent and more or less elongated as a plasmodiocarp. This species is reported from the United States, but I have seen no specimens. 7. DIDYMIUM PHYSAROIDES, Pers. Sporangia roundish or hemispheric, more or less irregular and deformed, sessile or with a very short stipe, and closely crowded together upon a strongly-developed common hypothallus; the wall a dark colored membrane, with a thin layer of stellate crystals of lime. The columella large and thick, divided into cells which are filled with irregular lumps of lime, common to all the sporangia. Capillitium of stout threads, usually simple, only rarely branched, furnished with numerous fusiform swellings. Spores globose, minutely warted, dark violaceous, 12-14 mic. in diameter. Growing on old wood, bark, moss, etc. Reported from Carolina by Curtis. It is said superficially to resemble somewhat _Physarum didermoides_.