Plasmodiocarp bent or short-flexuous, often arcuate or completely annular, dark chestnut brown or black, opening irregularly; peridium thin, brittle, translucent, covered without by a rather dense layer of brownish or black brown scales; capillitium of long, sparingly branched threads furnished with projecting spinules remarkable for their length, about twice the diameter of the thread; spores yellow, minutely but distinctly warted, about 12 .

This is the common species everywhere on the inner side of the bark of fallen trees, _Ulmus_, etc. It is readily distinguished 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 circ.u.mscission 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-ma.s.s and capillitium yellow, the capillitium well developed, of slender yellow threads of various widths, almost smooth; spores minutely warted, 10-12 .

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 mm., crowded, polygonal or quadrangular, depressed, but not flattened, smooth, bright rufous or brown; the peridium rather thick, yellow within, the dehiscence circ.u.mscissile; capillitium scanty, of slender, sparingly branched filaments, the surface minutely roughened, warted or spinulose; spore-ma.s.s yellow; by transmitted light pale yellow, 9-11 .

Differs from the preceding by the much smaller size of the sporangia, different color and habit. The sporangia, while depressed, still maintain considerable rotundity; they are occasionally quite spherical, and then of very uneven size, hardly in contact. In some cases the plasmodium before maturing seems to a.s.sume the form of a plasmodiocarp, which, by transverse fission at intervals, forms the curious four-sided conceptacles. At other times the plasmodium a.s.sumes the shape of a flat cushion or plate, which then subdivides into minute polygonal segments.

This form has been known some years to collectors, and, if named at all, has been called _P. irregularis_. Lister, _l. c._, a.s.sures us that Berkeley's type "is typical _P. depressa_."

Not common. Pennsylvania, Ohio, Illinois, Missouri.

3. PERICHAENA CORTICALIS (_Batsch_) _Rost._

PLATE II., Figs. 1, 1 _a_, 1 _b_.

1783. _Lycoperdon corticale_ Batsch, _Elench. Fung._, p. 155.

1875. _Perichaena corticalis_ (Batsch) Rost., _Mon._, p. 293.

1817. _Perichaena populina_ Fries, _Symb. Gast._, p. 12.

Sporangia sessile, gregarious, flattened, hemispherical; peridia simple, opening by a lid; dehiscence circ.u.mscissile, the upper part chestnut brown, the lower almost black; capillitium feebly developed, smooth, attached to the lid and usually coming away with it, bringing the brilliantly yellow spore-ma.s.s, and leaving a delicate, shining cupule adherent to the substratum; spores yellow, nearly smooth, 10-12 . On and under the bark of dead elms of various species.

A very handsome little species occuring rarely with us, or perhaps overlooked by virtue of its protective coloration. Found sometimes on the inner side of the bark where the latter has separated, but not yet wholly parted company with the wood. In such situations the tiny sporangia are so nearly quite the color of the moist substratum as to escape all but the closest scrutiny. The dehiscence is very remarkable, characteristic, beautiful. Black, brown, chestnut, and gold are harmoniously blended, in the opening coffers. Prior to maturity the future line of fission is plainly indicated by the difference in color.

This is clearly the species found by 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, h.o.a.ry canescent, sessile; peridium rather thick, persistent, circ.u.mscissile 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 ma.s.s dull yellow, by transmitted light pale, nearly smooth, 14-15 .

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 circ.u.mscissile. 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. LACHn.o.bOLUS

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

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

=1. Lachn.o.bolus= _Fries_.