1248 Wisconsin Academy of Sciences, Arts and Letters. 
Diderma persoonii Macbr. 
1899. Diderma Persoonii Macbride, N.-A. S.-M. p. 96. 
Macbride: ‘ * Sporangia sessile,, gregarious or closely aggregate, 
depressed, roundish, elliptical, elongate or plasmodiocarpous; 
outer peridium pure white, smooth, fragile, remote from the inner, 
which is thin, ashen, or bluish, and inclined to iridescence; colu¬ 
mella alutaceous or brownish, not distinguishable from the base 
of the fructification, the so-called hypothallus; eapillitium very 
scanty, short and nearly colorless, simple or slightly forked; 
spores violet-brown, smooth, 10-15.5//.” He adds, as distinctive 
characteristics, that the inner peridium in good specimens shows 
a peculiar lustre of a coppery tinge unlike anything else. The 
spores, also, he considers as immediately diagnostic, large, nearly 
smooth, dark purple-brown in color. 
Lister gives the plasmodium as colorless or yellow; sporangia 
scattered, pulvinate on a broad base or forming irregularly elon¬ 
gated plasmodiearps, smooth, white: columella none; the capilli- 
tium threads, he says, are flattened, usually broad at the base, 
branching dichotomously and slender above I he finds the spores 
usually faintly and closely warted, sometimes marked with 
stronger scattered warts, and 11-14// in diameter. He calls the 
species 7). dvjorme. 
Massee describes it as sessile on a broad base, convex, circular 
or irregularly elongated; columella absent or represented by a 
small accumulation of lime at the base of the sporangium.; eapilli¬ 
tium scanty, sometimes almost obsolete, threads springing from 
the base of the sporangium, slightly attenuated upwards, forked, 
pale brown or colorless; spores globose, smooth, dingy violet, 
10-13//. in diameter. 
In the one set of abundant specimens which I have I find no 
pulvinate sporangia, but many of the other forms mentioned 
above. The eapillitium is very scanty and short; the spores are 
dark violet-brown, very minutely and closely warted, and I find 
them from 12 to 14//, in diameter. This collection was found 
growing on dead leaves of several kinds, and on dead twigs near¬ 
by, in the campus woods, July 20, 1904. 
