, forming an elastic net;
spores purple-brown, minutely spinulose, 10-12 mu.

Resembling plasmodiocarpous forms of _D. squamulosum_, a montane var.;
small and delicate, our specimen about 16 x 6 mm. Evidently not common;
collected but once by Professor Bethel at an altitude of 11,000 feet,
Rocky Mountains of Colorado.

Reported in Switzerland and Sweden.

In certain Swiss gatherings made in 1913 Miss Lister finds capillitial
threads with _spiral_ taeniae as in _Trichia_! (_Jour. of Bot._, Apr.
1914.) The threads in our specimen are roughened, somewhat as in _D.
squamulosum_, though less strongly; the spores are nearly smooth,
fuliginous at first, paler and violaceous when saturate.

4. DIDYMIUM FULVUM _Sturgis._

1917. _Didymium fulvum_ Sturgis, _Mycologia_, IX., p. 37.

Sporangia gregarious, sessile, elongate or forming curved
plasmodiocarps, sometimes confluent, rarely sub-globose, concave
beneath, pale-raw-umber in color, 0.5-0.8 mm. in diameter, occasionally
seated on a concolorous, membranous, lime-encrusted hypothallus which
may form pseudo-stalks; sporangium wall membranous, stained with yellow
blotches, thickly sprinkled with clusters of large acicular crystals of
pale-yellowish lime; columella very much flattened or obsolete;
capillitium an abundant network of delicate, almost straight or
flexuose, pale-purple or nearly hyaline threads, frequently with dark,
calyciform thickenings as in _Mucilago_, and occasionally showing
fusiform, crystalline blisters; spores dark-purplish-brown, coarsely
tuberculate, the tubercles usually arranged in curved lines, paler and
smoother on one side, 12.5 to 14.5 mu. Colorado.

5. DIDYMIUM CRUSTACEUM _Fr._

1829. _Didymium crustaceum_ Fr., _Syst. Myc._, III., p. 124.

Sporangia closely aggregated, globose, or by compression deformed,
sessile, snow-white, by virtue of the remarkably developed covering of
calcareous crystals by which each sporangium is surrounded as if to form
a crust, the peridium membranous, colorless, usually shrunken above and
depressed; columella pale, small, or obsolete; hypothallus scant or
vanishing; capillitium of rather stout violaceous threads seldom
branched except at the tips, where they are pale and often bifid, or
more than once dichotomously divided; spores strongly warted, globose,
violet-brown, 10-13 mu.

This species has in some ways all the outward seeming of a diderma, but
cannot be referred to that genus because of the c