102 ENDOSPOREAE [DIDERMA 



membranous inner layer ; under surface rugose, thickened. 

 Stalk ochraceous or brownish, 0-2 to 0*8 mm. long, 0-25 mm. 

 thick, furrowed with wrinkles which are continued over the flat 

 under side of the sporangium, densely calcareous, often seated 

 on a white hypothallus. Columella indefinite, consisting of the 

 broad thickened base of the sporangium, flesh-red or flesh- 

 brown, charged with calcareous deposits in the form of nodules 

 and large rhomboidal crystals. Capillitium consisting of slender 

 colourless threads, variously branched and anastomosing, 

 or of violet-brown threads 1 to 2 //, thick, sparingly branched 

 except at the pale extremities. Spores pale violet-brown, 

 almost smooth, 7 to 9 /x diam. — Macbr. N. Am. Slime-Moulds, 

 101 (1899). Beticularia hemispherica Bull. Champ., 93, t. 446, 

 fig. 1 (1791), in part ; Sow. Engl. Fung., t. 12. Physarum 

 depressum Schum. Enum. PI. Saell., ii. 202 (1803) ; P. 

 Michelii Corda Icon. Fung., v. p. 57, tab. iii, fig. 33 (1842). 

 Didymium hemisphericum Fr. Syst. Myc, iii. 115 (1829), in 

 part. D. Michelii Lib. PI. Arduen. Exsic, fasc. ii. no. 180 

 (1832). Diderma depressum Fr. I.e., 108 ? Chondrioderma 

 Michelii Rost. in Fuckel Symb. Myc, Nachtr., ii. 74 (1873) ; 

 Rost. Mon., p. 172 ; Mass. Mon., 204 ; Lister Mycetozoa, 

 79. C. Friesianum Rost. I.e., 172 ? C. hemisphericum 

 Torrend Fl. Myx., 163 (1909). 



PI. 83. — a. sporangia (England) ; b. capillitium with fragment of sporangium- 

 wall and spores ; c. capillitium of stouter form ; d. nodules of lime from the stalk ; 

 e. spore. 



This species is abundant in the British Isles. It differs from Diderma 

 effusum in the larger discoid sporangia being provided with stout pale 

 stalks, which are rarely entirely absent in any development. D.. 

 depressum Fr. is described as having regular orbicular sessile sporangia 

 with a thick white fugaceous outer peridium ; it was probably a sessile 

 form of the present species, but may possibly be referred to D. effusum. 



Hob. On dead leaves and twigs. — Lyme Regis, Dorset (B.M. 1298) ;. 

 Batheaston, Somerset (B.M. 47); Yorks (B.M. 1112); France (Paris 

 Herb.) ; Belgium (B.M. 513) ; Germany (Strassb. Herb.) ; Sweden 

 (K. 1449) ; Portugal (B.M. 2376) ; Ceylon (K. 1440) ; Java (Herb. 

 Penzig) ; South Carolina (B.M. 890) ; Pennsylvania (B.M. 1299) ; 

 California (B.M. 2377) ; Antigua (B.M. 1661). 



3. D. effusum Morg. Myx. Miami Valley, 71 (1894) (non 

 Link). Plasmodium white. Sporangia sessile, gregarious, 

 much depressed, smooth, white, either rounded, 0-7 mm. diam., 

 or more usually forming elongated and flat branching net-like or 

 effused plasmodiocarps, sometimes 6 cm. long and 1 cm. or more 

 broad ; sporangium-wall of two layers, the outer a thin fragile 

 crust of globular lime-granules, separating from the membran- 

 ous colourless inner wall. Columella pulvinate, depressed, 

 brownish flesh-coloured, enclosing white lime-granules. 

 Capillitium consisting of delicate colourless or pale purplish 



