128 ENDOSPOREAE [DIDYMIUM 



No writers before Rostafinski make any mention of the characteristic 

 vesicles of the capillitium, and the reference-! to Batsch and Fries 

 quoted above might apply as well to plasmodiocarp forms of D. 

 squamulosum which D. complanatum often superficially resembles. The 

 reference by Albortini & Schweinitz to the yellow plasmodium of Phy- 

 sarum confluent (J muscigenum (I.e.) makes it probable that they were 

 describing the present species in part at least. The drawing of the 

 capillitium in Mr. Massee's Monograph (fig. 56) of D. complanatum 

 does not represent the characteristic vesicles, and the specimens from 

 Kew, Batheaston, and Carlisle in his collection quoted by him under 

 this name (I.e. 234) are plasmodiocarp forms of D. squamulosum. These 

 vesicles are frequently traversed by the capillitium threads, and 

 are apparently formed later than the capillitium ; like the spores, they 

 are minutely warted. 



Hab. On dead leaves. — Lyme Regis, Dorset (B.M. 2467) ; Flit- 

 wick, Beds (B.M. 2468) ; Lynton, Devon (B.M. 1328) ; North Wales 

 {B.M. 2469) ; France (B.M. 2472) ; Germany (B.M. 1329) ; Portugal 

 (B.M. 2471); Switzerland (B.M. 2470); Philadelphia (B.M. 1330). 



6. D. Clavus Rost. Mon., p. 153 (1875). Plasmodium grey 

 or colourless. Total height 0*4 to 0*8 mm. Sporangia 

 scattered, disc-shaped, stalked, erect, 0-7 to 1 mm. diam., 

 0*2 mm. thick, greyish- white ; sporangium-wall membranous, 

 more or less spotted with reddish-brown and beset with super- 

 ficial clusters of stellate crystals of lime above, thickened and 

 brown at the base. Stalk cylindrical, longitudinally striate, 

 pale brown or black. Columella none, or represented only 

 by the thickened base of the sporangium-wall. Capillitium 

 profuse, consisting of sparingly branched colourless or purple- 

 brown threads. Spores pale violet-brown, almost smooth, 5 to 

 8 /i diam.— Mass. Mon., 230 ; Macbr. N. Am. Slime-Moulds, 90. 

 Physarum Clavus Alb. &Schw. Consp. Fung., 96 (1805). Reticu- 

 laria hemispherica Bull. Champ., p. 93, pi. 446, fig. 1, in part ? 

 Didymium melanopus (3 Clavus Fr. Syst. Myc, iii. 114 (1829). 

 D. hemisphericum Fr. I.e., 115, in part ? D. commutabile 

 Berk. & Br. in Journ. Linn. Soc, xiv. 83 (1873) ; Rost. Mon., 

 App. p. 21. D. radiatum Mass. I.e., 229 (1892), in part. D. 

 neglectum Mass. (non Berk. & Br.) I.e., 231. D. Masseeanum 

 Sacc. & Syd. Syll. Fung., xiv. 836 (1899). 



PI. 108. — a. b. sporangia (England) ; r. capillitium and spores with fragments of 

 the upper and lower sporangium-walls ; d. spore. 



The characters of the type of D. commutabile Berk. & Br. from 

 Ceylon (B.M. 537) agree in all respects with those of the present 

 species, except that the stalk is 1*5 mm. long, and is encrusted with 

 deposits of lime. The type of D. neglectum Mass., from Philadelphia, 

 growing with Physarella oblonga, in Herb. Massee, is a slender form of 

 D. Clavus ; all the sporangia have the upper wall broken and the 

 spores shed, but sufficient remains to indicate the discoid form ; the 

 sporangium-wall is faintly mottled with brown ; the capillitium is 

 slender, the spores pale violet-brown, 5 to 6 jn diam. 



