m_.

10. DIDERMA DIFFORME, Pers. Plasmodiocarp roundish, oblong, or more or
less elongated and flexuous, scattered or seriately disposed; the
hypothallus a thin brownish membrane, or commonly not apparent. The
outer calcareous layer of the wall snow-white, thin, smooth, distinct
from the inner membrane, breaking into pieces and falling away; the
inner membrane thin, opaque and bluish or pellucid and iridescent.
Columella reduced to a thin layer of scales and granules upon the
brownish basal membrane. Capillitium scanty, consisting of short nearly
colorless threads, which are simple, or fork a time or two. Spores
globose, even, dark violaceous, 10-13 mic. in diameter.

Growing on bark, leaves, twigs, herbaceous stems, etc. Plasmodiocarp
.3-.5 mm. in thickness and variable in length, sometimes elongated
several millimeters.

11. DIDERMA RETICULATUM, Rost. Plasmodiocarp very much depressed,
roundish, oblong, much elongated and flexuous, closely crowded together
and confluent; the hypothallus a thin white granulose layer of lime,
scarcely broader than the plasmodiocarp. The outer calcareous layer of
the wall white, distinct, very fragile and easily shelling off; the
inner membrane much shrunken and withdrawn from the outer coat,
rugulose, cinereous, with a dense closely-adherent layer of granules of
lime. The columella a thin alutaceous, granulose-roughened layer,
extending along the base of the plasmodiocarp. Capillitium of threads
short and very slender, colorless, somewhat branched. Spores globose,
even, pale violaceous, 6-8 mic. in diameter. Plate XII, Fig. 47.

Growing on old wood, leaves, twigs, etc. Plasmodiocarp .5-.8 mm. in
width, much flattened and usually closely crowded. The rough calcareous
base of the plasmodiocarp might be considered as either all columella or
all hypothallus, with the upper surface leather-colored. I am indebted
to Arthur Lister, of London, for the determination of my specimens.

12. DIDERMA EFFUSUM, Schw. Plasmodiocarp very much flattened,
longitudinally creeping and reticulate or altogether widely effused;
hypothallus none. The wall very thin, smooth, white or cinereous, the
thin membrane covered by a single layer of closely-adherent granules of
lime, rupturing irregularly. The columella reduced to a thin alutaceous
layer of granules of lime, forming the base of the plasmodiocarp.
Capillitium of short colorless threads, extending from base to wall,
the extremities branched and connect