ed at sight by the
peculiar annular, looped, and U-shaped plasmodiocarps, with their dark
umbrine or blackened surface. From the preceding it is especially
distinguished by the spinulose capillitium and larger spores.

Not rare. New England, New York, Pennsylvania, Ohio.

=2. Perichaena= _Fries_

1817. _Perichaena_ Fries, _Symb. Gast._, p. 11.

Sporangia flattened, sometimes small and roundish, more often larger,
polygonal by mutual interference, or irregular, the peridium thickened
outwardly by a dense reddish or brownish layer of scales; dehiscing by
circumscission or by a lid; capillitium often scant, of slender, warted,
yellowish threads, attached betimes to the upper wall; spores yellow,
oval or spherical.

=Key to the Species of Perichaena=

_A._ Sporangia plainly flattened.

_a._ Very flat, sporangia 1mm. or more in width 1. _P. depressa_

_b._ Depressed; sporangia smaller 2. _P. quadrata_

_B._ Sporangia more or less spherical

_a._ Chestnut brown 3. _P. corticalis_

_b._ Gray or canescent 4. _P. marginata_

1. PERICHAENA DEPRESSA _Libert._

PLATE XVII., Fig. 10.

1837. _Perichaena depressa_ Lib., _Fl. Crypt. Ard._, IV., No., 378.

Sporangia sessile, applanate, crowded, polygonal by mutual contact,
fuscous or chestnut brown, shining, opening by a definite lid;
spore-mass and capillitium yellow, the capillitium well developed, of
slender yellow threads of various widths, almost smooth; spores minutely
warted, 10-12 mu.

Easily recognized by the peculiar, polygonal, depressed-flattened
sporangia and consequent shallow spore-cases in which lie the yellow
spores and scanty capillitium. Rostafinski refers here _P. vaporaria_
Schw., No. 2311, but the meagre description seems rather to apply to the
next species. The original material is no longer accessible.

In the crevices and on the inside of bark of fallen logs of various
sorts, walnut, maple, etc.

Not commonly collected. Specimens are before us from New England,
Illinois, Iowa, Missouri, Florida, Mexico, Nicaragua. Probably over the
whole wooded region of the continent.

2. PERICHAENA QUADRATA _Macbr._

1893. _Perichaena irregularis_ Berk. & C., Morgan, _Jour. Cin. Soc._,
p. 20.

Sporangia very small, less than 1/2 mm., crowded, polygonal or
quadrangular, depressed, but not flattened, smooth, bright rufous or
bro