ark. Sporangium .6-1.0 mm. in diameter, the
stipe usually shorter than the diameter, sometimes very short; the
lime-nodules about the thickness of the spores. This is a larger and
rougher species than _P. leucophaeum_, the sporangium is more often
irregular and the spores darker colored. _P. confluens_ and _P.
connexum_ of Link.

8. PHYSARUM COMPRESSUM, A. & S. Sporangium laterally compressed and much
flattened, subreniform, stipitate or subsessile; the wall a thin
violaceous or brownish membrane, rugulose, thickly covered with small
white roundish nodules of lime, similar to those in the capillitium.
Stipe short, brown or blackish at least below, sometimes pallid or
grayish above, longitudinally rugulose. Capillitium of slender tubules,
forming a loose net-work; the nodules of lime small, white, very
numerous, roundish or ellipsoidal, often confluent end to end. Spores
irregularly globose or angular, minutely warted, dark violaceous, 11-14
mic. in diameter.

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