100 
ENDOSPOREyE. 
[didymium. 
Phijsarum Tiossilaginis Berk, & Br., in Ann, Mag, Nat, Hist., 
Ser, 4, xvii., p, 139, Didymium Tussilaginis Mass.j Mon,, p, 244. 
Plate XL., A.— a. sporangia, stalked forms, x 20 ; b. sessile sporangia, 
one is broken and shows the white columella, x 20 ; c. plasmodiocarp form 
without columella, x 20 ; d. various forms of capillitium and spores, with 
fi-agment of sporangium-wall, x 280 ; e. spore, x 600 (England), 
The varieties which occur in this common species have led to different 
forms receiving specific rank. Observations conducted for a length of 
time on large growths among one heap of leaves show that the colour 
of the capillitium varies from almost black to colourless in the same 
locality ; a cluster on one leaf may present several shades, and even 
in a single sporangium one-half of the capillitium may be dark and 
the other half colourless ; this difference of colour is seen in all forms, 
from the stalked sporangia to effused plasmodiocarps. The stalk and 
columella may vary from white to bright orange. The characters given 
as distinguishing D. squamulosum, D. macrospermum, D. discoideum, 
D. ^^rcBcoar, and D. Fuclceliamm are so inconstant that they cannot 
be applied to mark even varieties of D. effusum. In the specimen 
of D. effusum Rost. (= D. confluens Rost., Mon., App., 22), in Strassb. 
Herb., the sporangia are stalked or sessile, with delicate white capil- 
litium. In the sporangium examined the thi'eads in one portion are 
without any thickenings ; in the remaining part there are numerous 
small fusiform expansions apparently containing lime, as is not infre- 
quent in this species ; the spores are minutely spinulose. The 
specimen of D. macrospermum in Strassb. Herb, has colourless capillitium 
springing from a large white columella ; the spores are strongly spinu- 
lose, 10 to 11 diam. ; the size of the columella in D. effusum is 
very variable, and the large development in the Strassburg specimen 
of D. macrospermum is by no means exceptional ; the roughness of the 
spores is the only feature which deviates from the usual forms of 
D. effusum, but as the spores of that species vary from nearly smooth 
to spinose in the same heap of leaves, and present all intermediate 
degrees of difference, this character cannot be taken as distinctive. 
D. iw(zcox is described as having two walls ; the type specimen at 
Strassburg is the frequent form of D. effusum, with the crust of 
crystals on the sporangium- wall wrinkled and scaly, but the wall itself 
is membranous and single. D. discoideum and D. FucJcelianuin are 
given as distinguished by the coloured stalk, columella, and capiUitium, 
and by the spotted sporangium-wall ; these characters are met with 
in different degrees in sporangia of D. effusum, associated with 
those having white stalks and those with colourless walls and capil- 
litium. The type of D. radiatum Berk. & Curt. (K. 1516) is nearly 
destroyed ; only the stalks remain, but these are characteristic of 
D. effusum, being white and spreading at the base, deeply furrowed 
and granular with deposits of lime ; Berkeley's description of the 
capillitium and spores is not at variance with frequent forms of this 
species. Chondrioderma Alexandrowiczii Rost., the type specimen of 
which is in the Strassburg Herb., is probably a form of D. effusum ; 
the sporangia are sessile, with the capillitium and spores of that species ; 
it differs from the type in the almost entire absence of lime. A 
specimen from Lyme Regis has the sporangium-wall similar to that 
of the Strassburg specimen ; in both cases it is membranous with 
cloudy spots of brown, and with calcareous deposits in the form of 
scattered minute spicules; the capillitium in both is violet-brown, 
beset with short spines, and colourless at the extremities ; the colu- 
mella in both is represented by a brown thickening of the base without 
