e as an _exsiccata_. The
evanescent peridium is colorless; when free, white or silvery.

8. COMATRICHA NIGRA (_Pers._) _Schroeter._

PLATE XI., Figs. 1, 2, 3.

1791. _Stemonitis nigra_ Pers., Gmel., _Syst. Nat._, p. 1467.
1801. _Stemonitis ovata_, var. _nigra_ Pers., _Syn._, p. 189.
1863. _Stemonitis friesiana_ DeBy., _Rab. Eur. Fung._, No. 568.
1875. _Comatricha friesiana_ (DeBy.) Rost., _Mon._, p. 200.
1889. _Comatricha nigra_ (Pers.) Schroeter, _Pilz. Krypt. Fl.
v. Schles._, I., p. 118.
1894. _Comatricha obtusata_ Fr., Lister, _Mycetozoa_, p. 117.
1899. _Comatricha nigra_ (Pers.) Schroeter, Macbr., _N. A. S._,
p. 128.

Sporangia scattered, ferruginous or dark brown, globose or ovoid,
stipitate; stipe long, hair-like, tapering upward, black; hypothallus
none; columella rapidly diminished toward the top, at length dissipated;
capillitium of slender flexuous threads, radiating horizontally,
repeatedly branching and anastomosing to form an intricate dense
network, from the surface of which project a few short hook-like
peridial processes; spore-mass black, spores by transmitted light dark
violaceous, smooth or nearly so, 7-10 mu.

This species, when typical, is easily recognized by its almost globose
sporangia mounted on long slender stocks. These are 2 or 3 mm. high and
generally persist, as Persoon noticed, a long time after the sporangium
has fallen. The sporangia are at first black; after spore disposal pale
ferruginous. In shape they vary from ovate to spherical. Sometimes they
are umbilicate below, so that a vertical section would be obcordate.
Care must be taken to distinguish the present species from blown-out
forms of _Lamproderma_.

This most common species seems to be also the center of widest
differentiation. In a valuable paper on the Myxomycetes of Dr. C. H.
Peck's Herbarium Dr. Sturgis points out the varying relationships of a
group of surrounding forms. According to account _C. nigra_ verges on
one side to _C. laxa_, on the other to _aequalis_ which the Listers
enter as varietal here. However, in the former the more rigid, direct
and simple branching from the columella is usually determinative; in the
latter the color, form, and generally more delicate structure, and a
tendency to grow in tufts will serve to distinguish.

In this discussion we have assumed as typical the globose sporangium,
with the variations in the direction of ovate, obovate, ellipsoidal,