--in the
much firmer, more persistent, and less calcareous peridium, in the more
complex capillitium, in the darker and larger spores, and especially in
the peculiar and prominent columella, which is not only rough, but even
"sometimes spinulose even to the extent of long spicules penetrating to
one-third the height of the sporangia." _N. A. F._, 2493.

As stated under No. 8, these last two species are called varieties only
of _D. nigripes_. They are so retained in _Mycetozoa, 2nd ed._ Since,
however, they are the usual presentation of the species in the United
States, it seems wise to let them stand for the present, as here. They
are quite distinguishable; _D. eximium_ especially well marked.

Apparently rare, it yet ranges from New York to eastern Iowa, in
colonies rather large. Okoboji Lake;--fine!

13. DIDYMIUM TROCHUS _List._

1898. _Didymium trochus_ List., _Jour. Bot._, XXXVI., p. 164.

Sporangia plasmodiocarpous, hemispherical or turbinate, white, sessile
or very short-stalked, cream-colored or white; peridium double, the
outer shell-like, the inner membranaceous, more or less adherent to the
outer, both caducous together, leaving the thickened base surrounding an
expanded columella; stipe, when present, very short, stout; capillitium
colorless, nearly simple; spores brownish-purple, strongly warted, 9-10
mu.

On decaying leaves, rotten cactus, yucca, etc., Monrovia, California;
_Bethel_.

Reported from England on beds of leaves or straw; in Portugal Dr.
Torrend finds it on or _in_ dead leaves of _Agave americana_! Evidently
an American species, and belonging to arid regions; its occurrence in
England surprising!

14. DIDYMIUM ANNULATUM _Macbr. n. s._

PLATE XX., Figs. 4, 4 _a_.

Sporangia small, scattered, annulate, not only without columella but
perforate when the stipe is broken, umbilicate above and below, grey,
coated with crystalline frustules, opening irregularly about the
periphery; stipe white, or pallid, fluted, tapering upward from a
distinct hypothallus; capillitium scanty consisting of delicate,
sparsely branching threads, the branchlets anastomosing more or less at
length, attached to the peridial wall, radiating from the rim of the
slightly depressed top of stipe, without special thickenings save at the
insertion of the ramules a triangular enlargement is usual and of dark
or pallid shade; spores smooth; however they show three or four spots
on the hemisphere and other minute b