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Didymium effusum, Rost.
Sporangia densely aggregated or scattered, sessile on a hroad
base, circular or irregular in outline, depressed, wall grey, pruinose
with numerons minute crystals aggregated in masses; columella
hemispherical, white or pallid, rugulose; threads of capillitium
very slender, colourless or pale fuliginous,/iirm'sAerf with scattered
coloured protuberances, combined to form an irregular dense
net; spores globose, brownish-purple, minutely ivarted, 10—12 ju
diameter.
Didymium effusum, Rost., Mon., p. 163; Sacc., Syll., no. 1302.
On leaves, wood, &c. Britain (Cornwall); Finland ; Sweden ;
France; Germany; United States; Ceylon.
About '5 mm. diameter, characterized by the white columella,
tbe capillitium threads furnished witli numerous well-defined
projections in the form of thickened plates or pyriform swellings,
and the dense meal of crystals on the wall.
(Rostafinski’s Synonyms.)
Diderma effusum. Link, Obs. I., p. 42 (1809).
Didymium effusum, Fr., 1. c,, iii., p. 124 (1829).
Physarum confluens, Fr., Excl. Syn., 1. c., iii., p. 146 (1829).
Sub-Gen. Hemididymium.
Capillitium usually dense, threads branching and anastomosing
to form an irregular network throughout the capillitium, angles
usually flattened and more or less triangular.
The species included in the present sub-genus are distinguished
from those belonging to the sub-genus Didymium by
tbe absence of the simple or bifurcating threads at the basal
portion of tbe capillitium.
A. Sporangium stipitate.
* Spores smooth.
Didymmm longipes, Mass. (n. sp.) (fig. 226).
Sporangia small, globose, snow-white, frosted witb a few
scattered granules or crystals of lime; stem very long and
slender, erect, snow-white, very slightly attenuated upwards,
almost smooth, expanding at the base into a small, circular,
white hypothallus; columella absent; capillitium well-developed,
threads very thin, colourless, hranching and anastomosing irregularly
to form a network, nodes usually triangular; spores
globose, dingy lilac, smooth, 8—10 g diameter.
(Type in Herb. Berk., Kew, witb Tilmadoche nutans.)
On bark and wood. Britain (Yorks); Lower Carolina.
A very distinct species, characterized by its snow-white colour
throughout, 2’5—3 mm, high, sporangium very small. Spores
perfectly smooth under a xV objective.
Didymmm fulvellum, Mass. (n. sp.) (fig. 232).
Sporangia spherical, very little or not at all umbilicate,
stipitate, outer cretaceous coat pure white, composed of minute
granules which fa ll away in the form of powder, inner wall with-'
out lime, rather tough, bright fulvous; stem slender, elongated,
straight or slightly curved above, attenuated upwards, same
colour as inner wall of sporangium, much wrinkled longitudinally,
expanding at the base into a similarly coloured circular
hypothallus; columella brown, not very prominent; mass of
spores blackish with a purple tin g e ; capillitium copious, threads
repeatedly forked, 2—‘3 g thick, rather broader at the base of
each bifurcation, combined laterally to form an irregular network,
colourless; spores globose, smooth, pale dirty lilac, 8—10 g
diameter.
On fallen oak leaves; scattered or gregarious.
United States.
(Type in Herb., Kew.)
Sporangium 1 mm. diameter, stem about 2 mm. high.
Didymmm australis, Mass. (fig. 208).
Sporangium globose or slightly flattened above and below,
slightly umbilicate, at first with a thick, white layer of crystals
which soon breaks up into large, persistent, irregular patches;
stem thin, bright brown, slightly attenuated upwards, often bend