ulosum_ (Cke. & Balf.) Morg., _Jour. Cin. Soc._,
p. 87.
1899. _Physarum nodulosum_ Cke. & Balf., Macbr., _N. A. S._, p. 51.
1911. _Physarum pusillum_ List., _Mycetozoa, 2nd ed._, p. 64.

Sporangia gregarious; minute, globose, bluish-white, the sporangial wall
thin and more or less encrusted with lime, breaking up irregularly,
stipitate; stipe slender, longer than the sporangium, attenuate upward
or even, bright brown, rugose, expanded above into a shallow cup-like
base for the sporangium; columella none; capillitium with lime-knots
more or less abundant, white, often uniting, badhamioid; spore-mass
black; spores by transmitted light, pale lilac-brown, almost smooth,
10-12 mu.

Pennsylvania, Ohio, Iowa; Canada.

One of the smallest species of the genus, by its proportionally long
stipe and small round sporangium reminding one somewhat of _P.
globuliferum_; much smaller, however, and in every way different. The
generic characters are mixed, and the species has been accordingly
variously referred. The lower part of the peridium is sometimes
persistent after the dehiscence, and so far reminds of _Craterium_. But
this character is not constant, and even at best the persisting part is
very small, not greater than in _P. melleum_, for example. On the other
hand, the capillitium in some sporangia is strongly calcareous, reminds
of _Badhamia_, but in most sporangia the _Physarum_ characters are
sufficiently clear.

In the Kew Herbarium, it is said, are two American specimens under one
label, "_Didymium pusillum_." One specimen is a didymium indeed, but, as
it appears, _D. proximum_ Berk., already described. The other is a
physarum. It is proposed in _Mycetozoa, 2nd ed._, to use the combination
thus set free, as if applied by the original author to the second
specimen, _not_ didymium, and to make the new combination date from 1873
and so take precedence of the binomial applied in 1881 by Cooke and
Balfour here retained by the law of priority.

35. PHYSARUM MACULATUM _Macbr._

PLATE XIV., Figs. 6, 6 _a_, 6 _b_.

1893. _Bull. Lab. Nat. Hist. Iowa_, II., p. 383.
1899. _Physarum maculatum_ Macbr., _N. A. S._, p. 47.
1911. _Physarum tenerum_ Rex., Lister, _Mycetozoa_, p. 52, in part.

Sporangia scattered or gregarious, very small, .3-.4 mm., dull gray,
thin-walled, dotted with minute, white calcareous granules, stipitate;
stipe long, about 2 mm., stout, attenuated upward, striate
longitudinally or wr