agile, snow-white; the inner delicate, the dehiscence by
more or less regular longitudinal fissure. Capillitium strongly
developed with abundant white, calcareous granules. Spores smooth, dull
violet, 8-9 mu. Plasmodium pale gray, or nearly white.

Easily recognized at sight by its peculiar form, bilabiate and sinuous.
Apart from microscopic structure, perfectly described by Fries, _Syst.
Myc._, p. 145. Bulliard called it _Reticularia sinuosa_. Habitat
various, but not infrequently the upper surface of the leaves of living
plants, a few inches from the ground. The two sorts of fructification
often occur side by side, or merge into one another from the same
plasmodium. Where the substratum affords room the plasmodiocarpous style
prevails; in narrower limits single sporangia stand. The calcareous
deposit on the peridium is usually very rich and under a lens appears
made up of countless snowy or creamy flakes. Forms occur, however, in
which these outer calcic deposits are almost entirely wanting; the
peridium becomes transparent, the capillitium visible from without.
Judging from material before us, this appears to be the common
presentation in western Europe. See also No. 5 following.

Widely distributed. New England to the Carolinas, and Louisiana west to
South Dakota and Nebraska, Iowa and Washington.

5. PHYSARUM BITECTUM _List._

PLATE XIX., Fig. 16.

1891. _Physarum diderma_ Rost., List., _Jour. Bot._, XXIX., p. 260.
1894. _Physarum diderma_ Rost., List., _Mycetozoa_, p. 57.
1911. _Physarum bitectum_ List., _Mycetozoa, 2nd ed._, p. 78.

Sporangia gregarious, sub-globose, sessile or plasmodiocarpous, smooth
white or pallid, terete or somewhat compressed; peridium double, the
outer wall calcareous, free and deciduous above, recurved and persistent
below; the inner, smooth, pale purplish, more persistent; dehiscence
more or less irregular beginning at the top; capillitium of large white
nodules connected by short hyaline threads; spores generally spinulose,
violaceous brown, 9-10 mu.

As suggested by the author of this species it is properly a variety of
_P. sinuosum_; certainly is, as it presents itself in this part of the
world. Of the species last named we have compressed forms opening by
narrow fissure along their knife-edged summit, with scarce place for
capillitium at all between the approaching walls; again we have colonies
of sporangia quite terete, calcareous without, opening in fragmental
fas