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The granulose wall of the spoi’angimn separates the present
species from the genus Chondrioderma.
Didymium duhium, Eost. (fig. 102).
Plasmodium pulvinate, arcuate, in crowded clusters, the outer
wall white, loith stellate crystals of lime, breaking away from
inner wcdl in irregular pieces; threads of capillitium rigid,
rarely forking, forming a loose net, furnished with curved spines,
spores obscure violet, mimitely verruculose, 10—11 g diameter.
Didymium dutdum, Kost., Mon., p. 153; Sacc., Syll., n. 1298.
Britain (Lyndhurst); Bohemia.
Sub-Gen. Atricha.
Capillitmm obsolete ; columella absent.
The two species constituting tbe present subgenus are undoubtedly
degenerate species of Didymium, characterized by
tbe very rudimentary condition, or entire absence of tbe
capillitium.
Didymium sinapinum, Cooke (figs. 167,
Clavate, subcylindrical, or more or less irregular, wall brittle
with lime, at first compact, then breaking up into bright yelloio,
easily detached particles, becoming irregularly ruptured at the
apex, basal attenuated stem-like portion darker, often with a
purple tinge; liypotballus spreading, thin; mass of spores
blackish-purple; spores globose, dingy lilac, minutely warted,
7—9 g diameter.
Didymmm sinapinum, Cooke, Brit. Myx., p. 33, fig. 245;
Sacc., Syll, n. 1819.
(Type in Herb., Kew.)
On leaves. Wales (Foi'den).
Growing in isolated patches, gregarious or crowded, springing
from a common hypothallus,sporangia 1—I'o mm. high, usually
more or less clavate, now and then irregularly lobed and forming
a small aethalium consisting of two or three sporangia,
bright sulphur-yellow; in rare instances a few very thin, bifur-
Didymmm. 247
eating threads are present, but in most sporangia there is no
trace of a capillitium,
Didymium flavidum, Peck.
Sporangia globose, or broadly obovate, sessile on a broad or
narrow base, wall brittle with lime, rugulose, sulphur-yellow,
sometimes with a tinge of orange, becoming irregularly ruptured
at the apex, or the apical portion breaking away in an irregularly
circumscissile manner, basal half persistent; mass of spores
blackish-violet, spores globose, dingy lilac, very {minutely verruculose,
10—12 g diameter.
Didymium flavidum, Peck, 28th Report State Mus., N. Y.,
p. 54.
Physarum flavidum. Peck, Berl., Sacc., Syll., n. 1215.
(Authentic specimen from Peck, in Herb., Kew.)
On wood. United States.
Scattered or gregarious, about '5 mm. diam., springing from
a very thin hypothallus; capillitium consisting of a few scattered,
very thin, bifurcating threads, or most frequently entirely
absent.
Owing to imperfect diagnoses and absence of type specimens, the
folloioing cannot be arranged in their respective sections.
Didymium tenerrimum, B. and C.
Sporangium globose, white, venulose, umbilicate below; hypothallus
obsolete; stem elongated, thickened below, pallid, hyaline;
threads of capillitinm colourless ; spores black.
Didymium tenerrimum, B. and C., Linn. Soc. Journ., vol. x,,
p. 848.
Didymium obnisseum, Saco., SylL, n. 1195 (in part).
On leaves of grass, nearly allied to D. obrusseum, B. and C.
Cuba.
The present species is given as a synonym of D. obrusseum,
B. and C,, in Saccardo’s Sylloge, but as the authors considered
the two species to be distinct, and as uo specimen exists in
Berkeley’s Herbarium, I have considered it advisable not to