74 ENDOSPOREAE [PHYSARUM 



l>\ many intermediate gatherings into P. vcrnum Komm., which perhaps 

 is hardly more than a very robust variety with larger, darker spores. 

 When the sporangia are clustered and nearly destitute of lime, P. 

 dnen urn is with difficulty distinguishable from P. atrum Schwein. (q.v.). 

 Pln/.sttrnm cnnnlobatum Ditm. (in Sturm Deutsch. Fl., Pilzo, i. 40: 

 Fr. Syst. Myc, iii. 142) has been placed by Rostafinski as a synonym 

 for the present species; but the descriptions are too imperfect to be 

 instructive. From Berkeley's description of Didymium scrobiculatinti 

 Rostafinski was probably right in placing it under P. cinereum ; hardly 

 au\ t hing remains of the type from Swan River, Australia, hi Berkeley's 

 Herb. (K. 151 S). 



Hab. On dead leaves, etc. — Devon (B.M. 1244) ; Essex (B.M. 

 1243); Bedfordshire (B.M. 2208); Wiltshire (2207); Aberdeen 

 i B.M. 2211) ; France (Paris Herb.) ; near Berlin (B.M. 2209) ; Sweden 

 (B.M. 2210); Portugal (B.M. 2212); Italy (B.M. 1972); Ceylon (K. 

 1284) ; New South Wales (B.M. 2213) ; New Zealand (2214) ; Philip- 

 pine Islands (B.M. 2032) ; Japan (B.M. 2215) ; Pennyslvania (B.M. 

 1246); Iowa (B.M. 1245); South Carolina (B.M. 431); Brazil B.M. 

 2216); Antigua (B.M. 1652). 



41. P. atrum Schwein. in Trans. Am. Phil. Soc, n.s. 

 iv. 258 (1832). Plasmodium yellow, or white ? Sporangia 

 subglobose, 0*2 to 0*4 mm. diam., sessile, confluent, clustered 

 or heaped, dull violet-brown, often veined with white 

 or sprinkled with minute white warts ; sporangium-wall 

 membranous, pale purplish, with or without scanty 

 deposits of lime. Capillitium a sparse network of hyaline 

 threads with small angular or branching white lime-knots. 

 Spores brownish-violet, minutely warted, 10 to 12 /x diam. — 

 Morg. Myx. Miami Valley, 99 (1896) ; Macbr. N. Am. 

 Slime-Moulds, 36. P. reliculatum Berl. in Sacc. Syll. Fung., 

 vii. 350 (1888). 



PI. 64. — a. sporangia (New Brunswick) ; b. capillitium and spores with fragment 

 of sporangium-wall ; c. spore. 



It has been doubted if this is a distinct species, or if it may not be a 

 large-spored and almost limeless form in some cases of P. cinereum 

 in others of P. virescens. The late Dr. Rex, who had wide experience 

 of North American Mycetozoa, wrote of it in 1892 : ' This, though 

 found in some quantity was probably abnormal ; I think it is probably 

 P. virescens with a minimum of lime." Prof. Farlow, writing in 1902, 

 observes that in July of that year, " this was by far the commonest 

 species on moss, dead leaves and twigs, in the fir woods on Campobello 

 Island, New Brunswick " ; he adds that the plasmodium was yellow, 

 but does not express a decided opinion as to the validity of P. atrum 

 as a species. Dr. Jahn has repeatedly gathered a similar form in 

 woods near Berlin, arising from white plasmodium. The capillitium is 

 often entirely limeless. With our present imperfect knowledge, it 

 would seem well for convenience to recognise Schweinitz's species ; 

 P. atrum here includes both the German and American gatherings. 



Hab. On dead wood, twigs, etc. — Berlin (B.M. 2277) ; New Bruns- 

 wick (B.M. 2279) ; New Hants (B.M. 2278). 



