DIDER3IA] PHYSABACEAE 99 



layer of the sporangium-wall cartilaginous, orange-brown, 

 usually with dense deposits of lime-granules on the inner 

 side, the inner layer a firm hyaline membrane, giving attach- 

 ment to the capillitium. Columella none. Stalk short, weak, 

 yellowish, translucent, arising from a membranous hypo- 

 thallus. Capillitium a network of rigid hyaline threads with 

 flattened expansions at the axils, connected with angular 

 branching and anastomosing brown lime-knots. Spores 

 spinulose, 11 to 13 /x diam., occasionally 15 to 20^ diam.. 

 sometimes slightly clustered, violet-brown or dark brown, 

 with a pale spot where dehiscence occurs. — Mass. Mon., 338 ; 

 Macbr. N. Am. Slime-Moulds, 81. Lycoperdon fragile Dicks. 

 PI. Crypt. Brit., i. 25, t. iii, fig. 5 (1785). Diderma verni- 

 cosam Pers. in Usteri Ann. Bot., xv. 34 (1795). D. atrovirens 

 Ft. Syst. Myc, iii. 103 (1829). Trichia lutea Trentep. in Roth 

 Catal. Bot., i. 230 (1797). Physarum nitidum Schum. Enum. 

 PI. Saell., ii. 205 (1803). P. vernicosum Schum. I.e., 206. 

 Leocarpus veniicosus Link I.e. ; Lister Mycetozoa, 75. L. 

 spermoides Link I.e. L. atrovirens Fr. Symb. Gast., 13 (1817). 

 L. ramosusFr. Summ. Veg. Scand., 450 (1849). Tripotrickia 

 elegans Corda Icon. Fung., i. 22, t. vi. f. 288a (1837). 



PI. 81 — a. sporangia (England); b. capillitium and spores with fragment of 

 sporangium-wall ; c. spore. 



The plasmodia of this species are frequently large, When about to 

 change into fruit they become orange-yellow, and often creep for a con- 

 siderable distance from their feeding grounds ; sporangia have been 

 found in one instance some feet up the trunk of a larch tree, and on 

 another occasion among the upper branches of a small furze bush. 

 Although abundant in temperate regions it does not appear to be 

 common in the tropics. 



Hab. On dead leaves, twigs, etc. — Hornsey, Middlesex (B.M. 22) ; 

 Epping Forest, Essex (B.M. 1285) ; Lyme Regis, Dorset (B.M. 1284) ; 

 near Edinburgh (B.M. 1061) ; France (B.M. 2373) ; Portugal (B.M. 

 2374) ; Belgium (B.M. 482) ; Germanv (B.M. 1059) ; Bohemia 

 (B.M. 489); Finland (B.M. 491); East* Tibet (Edinburgh Herb.); 

 Tasmania (K. 1390) ; Massachusetts (B.M. 1859) ; Iowa (B.M. 818) ; 

 Colorado (B.M. 2375) ; South Carolina (B.M. 495) ; Xew Grenada 

 (B.M. 1060). 



Genus 11. — DIDERMA Persoon in Roemer N. Mag. 

 Bot., i. 89 (1794). Sporangia stalked, sessile, or forming 

 plasmodiocarps ; sporangium-wall of two layers (single in 

 D. simplex), containing granular deposits of lime (except in 

 D. Trevelyani, q.v.). Columella usually present. Capillitium 

 threads simple or branched, without lime-knots. 



KEY TO THE SPECIES OF DIDEBMA. 

 Subgenus 1. — Etjdiderma : outer sporangium- wall a smooth 

 crust composed of lime granules densely compacted (except 

 in D. simplex) ; inner layer membranous (see also No. 13). 



