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.
Growing on old wood, mosses, etc. Sporangium about .5 mm. in diameter, the stipe once to twice this length. The species as here described includes Didymium ravenelii B. & C., Physarum simile Rost., and Physarum murinum Lister.
5. Cytidium globuliferum Bull. Sporangium globose, the base sometimes flattened or slightly umbilicate, stipitate; the wall a thin, pellucid membrane, covered with small scales of lime, white, cream-colored, or sometimes pinkish, breaking up and falling away at maturity. Stipe variable in length, white or smoky-white, usually darker below, rising from a thin hypothallus, tapering upward and entering the sporangium as a short obtuse or conical columella. Capillitium of slender tubules, forming a dense, persistent net-work of very small meshes, more or less expanded at the angles; the nodules of lime variable in size, numerous, white, roundish, ellipsoidal or obtusely angular. Spores globose, nearly even, pale violaceous, 7–9 mic. in diameter.
Growing on old wood, bark, mosses, etc. A very common and abundant species. Sporangium .5-.6 mm. in diameter, the stipe from once to two or three times this length. The lime nodules in the capillitium are sometimes round and quite minute, then again they are large and obtusely angular; the columella varies from very short and conical to longer and more cylindric. Diderma globuliferum of Fries S. M., Physarum albicans Peck. The specimens with the columella well nigh obsolete, may be Tilmadoche columbina Rost. [See Plate XIII. Fig. 55.]
6. Cytidium melleum B. & Br. Sporangium globose, stipitate or subsessile; the wall a thin yellowish membrane, rugulose, covered by large irregular scales of lime, honey-color to golden-yellow, breaking up irregularly. Stipe short, sometimes very short or nearly obsolete, snow-white, expanding at the base into a small white hypothallus, tapering upward and entering the sporangium as a short obtusely conical columella. Capillitium a loose net-work of delicate tubules with broad vesicular expansions containing much lime; the nodules numerous, white or sometimes yellow, large, irregular, lobed, and branched. Spores globose, nearly even, pale violaceous, 7–9 mic. in diameter.
Growing on old leaves, sticks, herbaceous stems, etc.; not uncommon in this region. Sporangium .4-.5 mm. in diameter, the stipe about the same length or much shorter. Didymium melleum B. & Br. Didymium chrysopeplum B. & C. also belongs here and not with C. citrinum.
§2. Rexiella. Sporangium ellipsoidal or pyriform, the columella prolonged nearly to the apex of the sporangium.