DIDYMIUM.] 
DIDYMIACE^. 
97 
the specimens the upper wall is broken and the spores are shed, but 
sufficient remains to indicate the discoid form of the sporangia ; the 
sporangium- wall is faintly mottled with brown ; the capiUitium is 
delicate, the spores pale violet-brown, 5 to 6 ja diam. 
Hab. On dead leaves, etc.— Batheaston, Somerset (B. M. 80) ; Lyme 
Regis, Dorset (L:B.M.74) ; Wanstead, Essex (L:B.M.74) ; Germany 
(Stt-assb. Herb.) ; Ceylon (B. M. 537) ; PhUadelphia (L:B.M.74). 
5. D. farinaceum Schrad., Nov. Gen. PL, p. 26 (1797). Plas- 
modium grey, among dead leaves, on bark, etc. Total height 
0-5 to 1 mm. Sporangia subglobose or hemispherical,^ deeply 
umbilicate beneath, stipitate, gregarious, 0"6 to 1 mm. diam., or 
nearly sessile and confluent, white or grey ; sporangium-wall firm, 
mottled with purple-brown, beset with stellate crystals of lime. 
Stalk cylindrical with a broad base, striate, dark brown, rarely 
rufous, 0-2 to 0-7 mm. long, 0-05 to 0-2 mm. thick, opaque and 
granular when mounted in glycerine. Columella large, hemi- 
spherical, umbilicate, dark brown, chambered, containing coarse 
granules of lime. CapiUitium of stout or delicate, sparingly 
branched or simple, more or less flexuose threads, colourless or 
purplish-brown, with dark calyciform thickenings. Spores dark 
purplish-brown or purplish-grey, with a thick spore-wall, nearly 
smooth or spinose, 7 to 11 )ii diam. — Eost., Mon., p. 154; Cooke, 
Myx. Brit., p. 31 ; Blytt, Bidr. K. Norg., Sop. iii. (1892), p. 7 ; 
Macbride, in Bull. Nat. Hist. Iowa, ii., p. 146 ; Mass., Mon., 
p. 219. Spumaria physaroides Pers., Syn. Pung., p. 163. 
Didymium physaroides Fr., Symb. Gast., p. 21 ; Post., Mon., 
p. 158 ; Cooke, Myx. Brit., p. 33 ; Mass., Mon., p. 233. 
a. genuinuni : threads of capillitium 2 /a thick; spores 9 to 11 
fx diam. 
p. minus: threads of capillitium 1 ix thick; spores 7 to 9 /x 
diam. 
Plate XXXIX., A. — a. sporangia a. gemdnum, x 20 ; h. capillitium and 
spores, with fragment of sporangium-wall and lime-crystal, x 280 ; c. spore, 
X 600 (England) ; cl. sporangia /3. minus, x 20 ; e. the same with heads 
confluent ; /. capillitium and spores, x 280 (England). 
Intermediate varieties uniting vars. /3 and a are so frequent that 
the former cannot be regarded as a distinct species. It is, however, 
very constant in its characters from different parts of the world, being 
marked by the smaller size and delicate capillitium. It often bears a 
considerable resemblance to D. nigripes, and is named D. microcarpum 
Host, in some specimens in Strassb. Herb. ; the opaque granular stalk 
distinguishes it from that species and its allies. Rostafinski's specimen 
of D. physaroides in Strassb. Herb, appears to be an imperfect develop- 
ment of D. farinaceum, as indicated by the spores, many of which are 
abnormal in shape and size, 15 to 50 /x long, combined in agglutinated 
masses, and by the capillitium, which contains vesicular expansions 
filled with lime-granules such as are not unfrequent in imperfect growths 
of Didymium ; the sporangia are mostly clustered and confluent, but 
in some cases they are solitary ; the columella is dark b-.'own and 
chambered, and the sporangium-wall is mottled with purple-brown. 
7 
