ber brown 14. _D. roanense_

ii. Peridium ashen 15. _D. radiatum_

iii. Peridium chocolate without,
inside white 17. _D. asteroides_

2. Sporangia stipitate.

_a._ Peridium pallid, smooth 18. _D. floriforme_

_b._ Peridium white, rugulose 19. _D. rugosum_

1. DIDERMA EFFUSUM (_Schw._) _Morgan._

1831. _Physarum effusum_ Schw., _N. A. F._, p. 257.
1896. _Diderma effusum_ (Schw.) Morg., _Jour. Cin. Soc._, p. 71.
1899. _Diderma effusum_ (Schw.) Morg., Macbr., _N. A. S._, p. 94.
1899. _Diderma reticulatum_ Rost., Macbr., _N. A. S._, p. 95.
1911. _Diderma effusum_ Morg., Lister, _Mycetozoa, 2nd ed._, p. 102.

Fructification plasmodiocarpous, reticulate, creeping, applanate and
generally widely effused, white; the peridium thin, cinereous, covered
by a delicate, white, calcareous crust; the columella simply the base of
the plasmodiocarp, thin alutaceous; the capillitium pale, consisting of
short threads somewhat branched toward their distal extremities; spores
smooth, pale violaceous, 8-10 mu.

This is _Physarum effusum_ Schw., _vid. N. A. F._, No. 2297. It is
reported by Morgan from Ohio, and we have one specimen from eastern
Nebraska, so that it is probably of general distribution in the eastern
United States.

This species was in the previous edition distinguished from the
Rostafinskian _P. reticulatum_ with spores a little smaller, 6-8 mu, and
with a much stronger tendency to the formation of definite sporangia,
elongate indeed and branching but often globose or depressed globose.
This we may know as,

VAR. RETICULATUM Rost.

1875. _Chondrioderma reticulatum_ Rost., _Mon._, p. 170.
1894. _Diderma reticulatum_ (Rost.) Morg., _Jour. Cin. Soc._, p. 71.

Sporangia gregarious, generally rounded, not much depressed, flat,
sometimes, especially toward the margin of a colony, elongate, venulose
or somewhat plasmodiocarpous, dull white, the inner peridium ashen or
bluish, remote from the calcareous crust, which is extremely fragile,
easily shelling off; columella indistinguishable from the base of the
sporangium, thin, alutaceous; capillitium of short, generally colorless,
delicate, sparingly branching or anastomosing threads perpendicular to
the columella; spores black in mass, by transmitted light violet-tinted,
smooth, 6-8 mu.

Perhaps