2. CYTIDIUM CITRINUM, Schum. Sporangium globose, the base slightly flattened or umbilicate, stipitate; the wall a thin membrane, covered with small scales of lime, yellow or greenish-yellow, breaking up and falling away at maturity. Stipe stout, erect, yellow, longitudinally rugulose, expanded at the base, tapering upward and entering the sporangium as a short obtusely conical columella. Capillitium of slender tubules, forming a dense net-work, with slight expansions at the angles; the lime-nodules numerous, roundish or ellipsoidal, variable in size, yellow. Spores globose, nearly smooth, violaceous, 7-8 mic. in diameter. Growing on bark, leaves, mosses, etc. Sporangium .5-.6 mm. in diameter, the stipe from once to twice this length. This, the typical species, I have not seen in this country, but forms with the sporangium lemon-yellow and grayish-yellow, with the stipe golden-yellow, connect it with _C. rufipes_. It is _Physarum citrinum_ Schum. _Diderma citrinum_ of Fries., S. M. 3. CYTIDIUM RUFIPES, A. & S. Sporangium globose, sometimes a little depressed and the base umbilicate, stipitate; the wall a thin membrane, covered with small scales of lime, golden-yellow to orange in color, breaking up at maturity and falling away. Stipe variable in length, slender, from orange or orange-red to dark red in color, sometimes blackish below, rising from a thin hypothallus, tapering upward and entering the sporangium as a short obtuse columella. Capillitium of slender tubules, forming a dense net-work of very small meshes, slightly expanded at the angles; the nodules of lime small, numerous, ellipsoidal or obtusely angular, orange to red in color. Spores globose, nearly smooth, violaceous, 8-10 mic. in diameter. Growing on old wood, mosses, etc. A very abundant species. Sporangium .5-.7 mm. in diameter, the stipe from once to twice as long. As here defined, the species includes _Physarum aurantium_ var. _rufipes_ A. & S., and _Physarum aureum_ var. _chrysopus_ Lev, which I am unable to keep separate; the variation in size of the spores is not in correspondence with the variations in color of the sporangia. _Physarum pulchripes_ Peck, and _Physarum petersii_ B. & C., mostly belong here. The bright orange colors become dull or tawny with age and exposure to the weather. 4. CYTIDIUM RAVENELII, B. & C. Sporangium globose, stipitate; the wall a thin pellucid membrane, covered with small scales of lime, from gray or drab to pale umber in color, breaking up at maturity and falling away. Stipe variable in length, concolorous with the sporangium or darker below, tapering upward and entering the sporangium as a short obtusely conical columella. Capillitium of tubules, forming a dense net-work of very small meshes, with slight expansions at the angles; the lime-nodules small, numerous, ellipsoidal or obtusely angular, gray or drab to pale umber in color. Spores globose, nearly even, pale violaceous, 7-9 mic. in diameter.