iderma
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 pin