oped, even
continuous, venulose, from stipe to stipe. The capillitium varies much
in abundance as in color; when scanty, it is colorless and in every way
more delicate, when abundant, darker in color and sometimes with
stronger thickenings.

_D. fuckelianum Rost._, as shown in _N. A. F._, 2090, and in some
private collections, seems to be a rather stout phase of the present
species; the stipe is more abundantly and deeply plicate, is sometimes
tinged with brown, and the capillitium is darker colored and coarser
than in what is here regarded as the type of the species; but withal the
specimens certainly fail to meet the requirements of Rostafinski's
elaborate description and figure, _Mon._, p. 161 and Fig. 154.

_D. effusum_ Link, probably stands for a sessile form of this species,
but Link's brief description (1816) is antedated by the much better one
of Albertini and Schweinitz, _l. c._

Generally distributed throughout the wooded regions of North America,
from New England to Nicaragua, and from Canada to California. Not
uncommon about stable-manure heaps, in flower beds, and on richly
manured lands. July, August.

Nicaragua specimens not only show a continuous vein-like hypothallus,
but have the peridia often confluent, the columellae in such cases
confluent, the stipes distinct. Furthermore, the largest spores reach
the limit of 12.5 mu, and perhaps the larger number range from 10-12.5 mu,
and all are very rough. This corresponds with _D. macrospermum_ Rost.,
which is distinguished, says the author (_Mon._, p. 162, _opis_),
"chiefly by the large and strongly spinulose spores." However, the same
sporangium in our Central American specimens yield spores 9.5-12.5 mu, a
remarkable range. So that _D. macrospermum_ on this side the ocean, at
least, cannot be distinguished from _D. squamulosum_, as far as spores
are concerned. A similar remark may be made relative to the form of the
columella which Rostafinski, in his figures especially, would make
diagnostic. The columella in the sporangia with largest and roughest
spores is that of a perfectly normal _D. squamulosum_.

7. DIDYMIUM MELANOSPERMUM (_Pers._) _Macbr._

PLATE VII., Figs. 3, 3 _a._

1794. _Physarum melanospermum_ Pers., _Roem. N. Mag. Bot._, p. 89.
1797. _Didymium farinaceum_ Schrader, _Nov. Gen. Pl._, p. 26, t. 5,
Fig. 6.

Sporangia gregarious, hemispheric, depressed, umbilicate below,
stipitate or sessile; the peridium firm, dull