ed together. Spores globose, even,
pale violaceous, 8-10 mic. in diameter. Plate XII, Fig. 48.

Growing on old leaves. The plasmodiocarp forms very much flattened
irregular patches from a few to several millimeters in length or extent.
I am indebted to Dr. Geo. A. Rex, of Philadelphia, for the
identification of my specimens, with those in the herbarium of
Schweinitz, under the name of _Physarum effusum_.

IV. LEPIDODERMA, DeB. Sporangium stipitate or sessile, sometimes
plasmodiocarp; the wall a thin, firm, colorless membrane, with an outer
layer of large scales consisting of bicarbonate of lime, the scales
either lying upon the wall or inclosed in lenticular cavities of the
membrane. Stipe present or absent; the columella usually conspicuous.
Capillitium of very slender threads, simple or outwardly branching at a
sharp angle, connected at the extremities. Spores globose, violaceous.

"In the present genus the carbonate of lime is present in the form of
very minute amorphous lumps until near to maturity, when it is dissolved
and reappears as bicarbonate of lime deposited in comparatively large
flakes."--_Massee._

1. LEPIDODERMA TIGRINUM, Schr. Sporangium large, much depressed,
hemispheric or lenticular, the base umbilicate, stipitate; the wall a
firm, dark colored membrane, variegated with large and small irregular
shining scales, greenish-yellow or straw color, rupturing irregularly.
Stipe stout, thick, erect, rugulose, ochraceous or ferruginous, variable
in length, expanding at the base into a thin hypothallus; the columella
brown, convex or hemispheric. Capillitium of slender, dark colored
threads, simple or sparingly branched, radiating from the columella to
the wall. Spores globose, minutely warted, dark violaceous, 10-13 mic.
in diameter.

Growing on old wood, moss, etc. Sporangium 1-1.5 mm. in diameter, the
stipe 1 mm. or less in length. This appears to be the only species of
the genus thus far discovered in this country.

EXPLANATION OF PLATE XII.

Fig. 37.--Didymium proximum, B. & C. _a._ Sporangium and stipe x 33.
_b._ Section through the columella.

Fig. 38.--Didymium eximium, Peck. _a._ Showing the rough columella of
one form. _b._ Section through the discoid columella of the very much
depressed form. Magnified by 33.

Fig. 39.--Didymium minus, Lister. _a._ Sporangium and stipe x 33. _b._
_c._ _d._ Sections through the columella showing different forms.

Fig. 40.--Didymium farinaceum, Schr. S