66 ENDOSPOREAE [PHYSARUM 



stalked, erect and ovoid, about 0*8 ram. high, 0-5 mm. broad, 

 or sessile, ovoid or subglobose, crowded, white, or dark grey 

 above from the falling away or discontinuance of the outer 

 calcareous crust ; sporangium- wall of three layers, the outer 

 a dense deciduous deposit of white lime-granules, the middle 

 layer a delicate colourless membrane with scattered lime- 

 granules, closely combined with an inner purplish, areolated, 

 thicker layer. Stalk variable in length and thickness, white, 

 membranous, not containing refuse matter and rarely 

 enclosing lime-granules, rising from a plicate white hypo- 

 thallus. Columella none. Capillitium consisting of numerous 

 rounded white lime-knots connected by short, seldom 

 branching hyaline threads, which are purple at the attach- 

 ments to the sporangium- wall. Spores very dark purple- 

 brown, closely and minutely spinulose, 10 to 13 //, diam. — 

 Mass. Mon., 291 ; Macbride N. Am. Slime-Moulds, 40. Spu- 

 maria ? didermoides Acharius in Pers. Syn., Addenda xxix. 

 (1801). Physarum conglobatum Fr. Symb. Gast., 21 (1818)? 

 P. lividum ft licheniforme Rost. Mon., p. 96 ; Mass. Mon., 304 

 (in part). P. cinereum var. ovoideum Sacc. in Michelia, ii. 

 334 (1882) ; Mass. Mon., 299. P. platense Speg. in Ann. Mus. 

 Nac. Buen. Aires, vi. 199 (1899) ? Spumaria licheniformis 

 Schwein. in Trans. Amer. Phil. Soc, n.s. iv. 261 (1832). 

 Claustria didermoides Fr. Summ. Veg. Scand., ii. 451 (1849) 

 Didymium congestum Berk. & Br. in Ann. Mag. N.H., ser. 2 

 v. 365 (1850). Badhamia ? pulcherrima Speg. in B. Acad. 

 Nac. Cienc. Cord., xi. 474 (1889) ? 



Var. lividum Lister, differs from the type in the grey 

 sporangia being always sessile and having usually a single 

 layer only to the sporangium- wall, in the lime-knots being 

 more angular, and in the rougher purple-black spores being 

 paler and smoother on one side. — Lister in Journ. Bot., 

 xxxvi. 161 (1898). 



PI. 45. — a. sporangia (Flitwick, Beds); b. capillitium and spores, with fragment 

 of sporangium-wall ; c. spore. 



PI. 46. — var. lividum ; a. sporangia (Flitwick, Beds) ; b. capillitium and spores, 

 with fragment of sporangium-wall ; c. spore. 



P. cinereum var. ovoideum Sacc. on Ailanthus glandulosa from Lyon, 

 leg. J. Therry (B.M. 432), is a short-stalked form of P. didermoides, with 

 sporangia arising from a white membranous hypothallus. P. lividum 

 var. licheniforme Rost., portions of the type of which from South 

 Carolina are in the Strassburg and Kew collections, is a sessile form of 

 P. didermoides. The var. lividum has hitherto been recorded only 

 from the county of Bedfordshire in this country. It was first observed 

 in April, 1897, on heaps of old straw near Luton by Mr. James Saunders, 

 who has since found it in half-a-dozen stations in that neighbourhood ; 

 it appears almost every year during the summer and autumn months, 

 often in great profusion, upon neglected straw heaps, sometimes in 

 company with the typical form. A specimen gathered near Lisbon by 



