diderma_ is a physarum despite its double wall. And so here
_Leocarpus_ was set out by its differentiating capillitium. In good
specimens of the present species a large part of the capillitial net is
entirely free from lime, so that when the peridium first opens at the
summit, sometimes no trace of lime appears; the calcareous deposits are
below, and tend to occupy not the nodal intersections as in _Physarum_,
but in large masses involve portions of the net itself, nodes and all,
as in _Leocarpus_. Miss Lister's beautiful figures, _op. cit._, Figs. 66
and 82, show this very well.

In The _Journal of Botany_, 52, p. 100, the distinguished author and
artist records the discovery of this species in the mountains of
Switzerland. She says: "This specimen shows a striking resemblance to
_Leocarpus fragilis_ Rost., both in the shape of the sporangia and in
the capillitium and spores; but although the color of the sporangia
varies in both these species, the walls of _P. (L.) fulvum_ are
membranous and rugose with included deposits of lime granules and show
nothing of the polished cartilaginous layers characteristic of _L.
fragilis_."

The species is a boundary type at best, and shows again how artificial
all our taxonomy is apt to prove, when the number of presentations of
some particular type becomes larger.

For these reasons, the present author writes _Physarum_, and believes
the question of identity in a perplexing case fortunately settled.

46. PHYSARUM VARIABILE Rex.

1893. _Physarum variabile_ Rex, _Proc. Phil. Acad._, p. 371.
1911. _Physarum variabile_ Rex, List., _Mycetozoa, 2nd ed._, p. 47.

Sporangia scattered, stipitate, sub-stipitate or sessile, about 1 mm.
high; regularly or irregularly globose, ellipsoidal, obovate or
cylindric-clavate in shape; sporangium wall sometimes apparently thick,
of a dingy yellow or brownish-ochre color, slightly rugulose on the
surface, crustaceous, brittle, rupturing irregularly, sometimes thin,
translucent, covered externally with flat circular calcic-masses falling
away in patches; stipes nearly equal, occasionally much expanded at the
base, rough, longitudinally rugose, variable in size, sometimes
one-third of a millimetre high, sometimes a mere plasmodic thickening of
the base of the sporangium; color of stipes varying from a
yellowish-white to a dull brownish-gray; capillitium a small-meshed
network of delicate colorless tubules with large, many-angled, rounded
mass