80 ENDOSPOREAE [PHYSARUM 



The present species is closely allied to P. conglomcratum, from which 

 it differs in the larger rougher spores and in the structure of the 

 sporarfgium-walL The type of Diderma ochroleucum Berk. & Curt. 

 from Pennsylvania (K. 1533) is typical P. contextum. 



Hab. On dead leaves and twigs. — Near Lyme Regis (B.M. 125.")) ; 

 near Birmingham (B.M. 1254); near Paris (B.M. 2307); Germany 

 (B.M. 4 IS); Sweden (B.M. 2308); Austria (B.M. 2306); Tasmania 

 (B.M. 2309); Iowa (B.M. 808); Wisconsin (B.M. 1876); Philadelphia 

 (B.M. 2310) ; Colorado (B.M. 2311). 



51. P. conglomeratum Rost. Mon., p. 108, figs. 73, 79, 

 90 (1875). Plasmodium ? Sporangia subglobose, sessile on 

 a broad base, densely aggregated on one plane, angled by 

 mutual pressure, 03 to 05 mm. broad, yellow or buffish- 

 white, mottled with paler shades ; sporangium-wall double, 

 the inner layer of the convex upper wall having translucent, 

 pale yellow curved thickened areas, with a vitreous fracture ; 

 the outer layer thick, Avith deposits of easily crumbling yellow 

 lime-granules. Capillitium consisting of delicate branching 

 hyaline threads, with numerous white or yellowish branching 

 often confluent lime-knots. Spores pale violet-brown, almost 

 smooth, 8 to 10 fx diam. — Macbr. N. Am. Slime-Moulds, 31. 

 Spumaria minuta Schum. Enum. PI. Saell., li. 196 (1803)? 

 S. granulata Schum. I.e. ? Diderma conglomeratum Fr. Syst. 

 Myc, iii. Ill (1829) ? D. minutum Fr. I.e. ? D. gramdatum 

 Fr. I.e., 110 ? D. flavum Weinm. Hymen. & Gasterom. 

 593 (1836) ? D. rugulosnm Weinm. I.e., 594 ? Leocarpus 

 granulatus Fr. Summ. Veg. Scand., 451 (1849) ? L. minutus 

 Fr. I.e., 450 ? Carcerina conglomerata Fr. I.e., 451 ? Physarum 

 Rostafinskii Mass. Mon., 301 (1892). 



PI. 56. — a. sporangia (Germany) ; b. capillitium and spores, with fragment ol 

 sporangium-wall ; c. spore. 



This species and the preceding are distinguished by differences in the 

 structure of the sporangium-wall and spores, — microscopic characters 

 that the earlier authors were unable to detect ; the synonymy quoted 

 above is therefore uncertain, and may refer in part to P. con- 

 textum. The vitreous structure of the inner wall of the upper part 

 of the sporangium is constant in all the specimens of the present species 

 that we have examined. Fries distinguished Diderma conglomeratum 

 from D. contextum 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 Physarum contextum the spores are rough and 

 measure 10 to '3 fx, while in P. conglomeratum they are nearly smooth 

 and measure 8 to 9 /x diam. He follows Fries in referring to a columella 

 in P. conglomeratum, but adds that it is free and not always evident, 

 and he describes P. contextum as being usually without a columella. 

 The specimen K. 1277 marked Diderma conglomeratum by Fries, 

 gathered in West Sweden, and taken by Mr. Massee as his type of 



