Growing on old stalks and leaves of _Zea mays_. Sporangium variable, .6-1.0 mm. in breadth, the stipe 1 mm. or less in length; the lime nodules about the thickness of the spores. According to Saccardo this species is the same as _Physarum nephroedium_ Rost. 9. PHYSARUM POLYCEPHALUM, Schw. Sporangia confluent into a subspheric gyrose-complicate head, composed of several to many laterally compressed, irregular, simple sporangia; the wall a thin, pellucid membrane, covered by a thin layer of minute scales of lime, white to yellow or greenish-yellow Stripes thin, flat, weak, and often prostrate, pale yellow, more or less connate, arising from a thin hypothallus. Capillitium of slender tubules forming a loose, irregular network, more or less expanded at the angles: the lime-nodules white or yellow, small, fusiform or by confluence elongated and sometimes branched. Spores globose, very minutely warted, violaceous, 8-10 mic. in diameter. Growing on old bark, wood, leaves, etc. The sporangia rarely simple, usually confluent into a head of from four or five to fifteen or twenty, and sometimes more, simple sporangia; the stipes variable in length, long or short, rarely wanting. The gray form is _Didymium polymorphum_ Mont., the yellow-green form _D. gyrocephalum_ Mont. Sprengel considered this species the same as _Physarum compactum_ Ehr., and it appears under this name in Schweinitz's _North American Fungi_; but Fries, who had seen specimens of both, disposed of them differently. 10. PHYSARUM DIDERMOIDES, Pers. Sporangia obovoid-oblong, stipitate, growing close together on a white membranaceous common hypothallus; the wall with a thick, white, outer layer of lime, easily crumbling and falling away, leaving the sporangium dark gray; the inner membrane rather thick and firm, violaceous, with a closely adherent layer of granules of lime. Stipes very short, white, thin, and weak, each formed by a bit of membrane arising from the hypothallus. Capillitium a loose net-work of slender threads, bearing numerous roundish or irregular white nodules of lime. Spores irregularly or angularly globose, minutely warted, dark violaceous, 12-15 mic. in diameter. Growing on wood, leaves, grass, etc. Sporangia .6-1.2 mm. in length by .4-.6 mm. in thickness, the stipe shorter than the sporangia. _Spumaria licheniformis_ Schw., belongs here. This is a truly abnormal species of _Physarum_, so much so that Fries, in the _Summa Veg. Scand._ placed it by itself in a separate genus, _Claustria_. _B. Sporangia sessile._