Batsch "ligni demortui putridi in
interiore corticis pagina." Bulliard has also described and figured the
species, _Sphaerocarpus sessilis_ t. 417, Fig. V.

The capillitium is nearly smooth; the spores are only slightly roughened
by minute warts.

Apparently not common. Iowa, Missouri; Black Hills, South Dakota;
Canada;--_Miss Currie._

4. PERICHAENA MARGINATA _Schweinitz._

1831. _Perichaena marginata_ Schw., _N. A. F._, No. 2319, p. 258.

Sporangia depressed, globose, polygonal as they become approximate or
crowded, hoary canescent, sessile; peridium rather thick, persistent,
circumscissile in dehiscence, covered without by minute whitish
calcareous (?) scales, within punctate by the imprint of the spores;
hypothallus distinct, white; capillitium scant or none! Spores in mass
dull yellow, by transmitted light pale, nearly smooth, 14-15 mu.

Lister, following Rostafinski, includes this form with the preceding.
The differences between the two forms are, it seems to us, sufficient to
make convenient their separation as by Schweinitz. Apart from the
peculiar incrustation in the present species, the larger spores, and
especially the peculiar white hypothallus, are distinctive. The method
of dehiscence is also different. In _P. corticalis_ the line of cleavage
before spore dispersal is indicated by a definite band surrounding the
sporangium. Nothing similar appears in the gray specimens of the present
form, although the dehiscence is quite as certainly circumscissile. The
habitat in American specimens is the _outer_ surface of the bark, which
causes the species generally, by protective coloration, to be
overlooked.

Not common. Pennsylvania, Ohio, Missouri.

_C._ ARCYRIACEAE

=Key to the Genera of the Arcyriaceae=

_A._ Peridium becoming fragmentary, but persisting;
capillitium non-elastic 1. LACHNOBOLUS

_B._ Peridium evanescent above, persistent below;
capillitium elastic 2. ARCYRIA

_C._ Capillitium elastic, bearing hamate branches 3. HETEROTRICHIA

=1. Lachnobolus= _Fries_.

1829. _Lachnobolus_ Fries, _Syst. Myc._, III., p. 177.

Sporangia distinct, sessile or nearly so, globose or cylindric, often
distorted, scattered or densely crowded, the peridium extremely thin,
ruptured irregularly, and persistent in fragments; capillitium attached
at numerous points to the sporangial wall, forming a dense net, the
t