PHYSARUM.] PHYSARACE/E. 59 



(B. M. 410 : K. 96) correspond with the description in his Monograph, 

 but in both of them the lime-knots, though somewhat confluent in the 

 centre of the sporangium, cannot be said to form a cylindrical columella, 

 such as he describes. The specimen from Fries (K. 1277) taken as the 

 type of this species by Massee (Mon., p. 304) is typical P. context um in 

 all the characters given by Rostafinski. The name P. Rostajinsli'i, 

 which is given by Massee as superseding P. conglomeration Rost., is 

 unnecessary. The vitreous structure of the inner wall of the upper 

 part of the sporangium is constant in all the specimens I have 

 examined. Fries distinguished Didtmui conglomeration from D. cn- 

 textum chiefly by the difference of the capillitium : he describes the 

 presence of a columella in both species, but speaks of the deposits of 

 lime as being more largely developed in D. conglomeratum. This is 

 an uncertain character, and varies in different gatherings. Rostafinski 

 was the first to detect the main specific difference, and pointed out 

 that in P1tyx<irtim contextum the spores are rough and measure 10 to 13 

 fj.. while in P. conglomeration they are nearly smooth and measure 

 8 to 9 p. diam. He follows Fries in referring to a columella in P. coti- 

 (jlonifi-utinii, but adds that it is free and not always evident, and he 

 describes P. co>tf< .'/<> //< as being usually without a columella. 



//<//>. On dead leaves, moss, etc. Darenth, Kent (B. M. 417) ; 

 Hutton, Yorks. (L:B.M.36) ; Germany (B. M. 415) ; Sikkim, India 

 (B. M. 4Hij. 



P. virescens Ditm., in Sturm, Deutsch. Fl. Pilze, vol. i., 

 p. 123, PI. Ixi. (1817). Plasmodium lemon-yellow, among dead 

 leaves ;m<l grass. Sporangia sul>irlobose or irregularly ovoid, 

 0*2 to 0*8 mm. broad, sessile, much aggregated in confluent groups, 

 or gregarious, rugose or nearly smooth, pale yellowish-green, 

 yellow, or olive-brown from the absence of lime; sporangium-wall 

 membranous, with dense innate clusters of minute yellow lime- 

 granules, rarely without lime. Columella none. Capillitium a 

 network of hyaline threads ; lime-knots fusiform, roundish or 

 irregular, yellow. Spores minutely spinulose, pale violet-brown, 

 6 to 9 /<, diam. Rost., Mon., p. 103 ; Cooke, Myx. Brit., p. 13; 

 Blytt, Bidr. Norg., Sop. iii. (1892), p. 4; Mass., Mon., p. 277. 

 P. Ditmari Rost., Mon., App., p. 8; Macbri.de, in Bull. Nat. Hist. 

 Iowa, ii., p. 155. P. thejoteum Fr., Symb. Cast., p. 21 (1818). 

 JDidymiumsinapinumCooke, Myx. Brit., p. 33; Mass., Mon., p. 246. 

 Physarum auriscalpium Macbride (non Cooke), I.e., p. 158. 



a. genumum : sporangia irregularly ovoid, 0'2 to 0'3 mm. broad, 

 in dense clusters of 20 to 30, on a membranous hypothallus, 

 shading from pale yellow-green to orange-yellow; sporangium- wall 

 with dense innate clusters of yellow^ lime-granules. Capillitium 

 often scanty. Spores 7 to 10 /JL diam. 



(3. obscurum : sporangia subglobose, 0*4 to O'G mm. diameter, 

 sessile, solitary, confluent, or plasmodiocarps, gregarious or 

 crowded, smooth or rugose, greenish, grey, or olive-brown and 

 somewhat glossy ; sporangium -wall membranous, colourless above, 

 yellow at the base, without lime, or with widely scattered innate 

 clusters of whitish lime-granules. Spores 6 to 8 //, diam. 



y. nitens : sporangia subglobose, - 5 to 0-8 mm. diam., sessile, 

 gregarious, not clustered, bright yellow. Spores 7 to 9 /JL diam. 



