138 ENDOSPOREAE [MUCILAGO 



more or less loosely compacted clusters from branching pro- 

 cesses of the membranous hypothallus, clothed with a thick 

 but fragile and deciduous white universal covering of crystals 

 of lime ; 2 to 6 cm. long, 1 to 6 cm. wide, and about 1 cm. 

 thick ; sporangium-wall membranous, purplish or colourless. 

 Columella membranous, hollow, compressed, following in 

 its branches the form of the confluent sporangia, sometimes 

 absent. Capillitium a network of widely branching anastomos- 

 ing stout purplish-brown or colourless threads, often with dark 

 calyciform thickenings, hyaline at the extremities where it 

 is attached to the sporangium-wall or columella ; the threads 

 are accompanied occasionally by tubular processes of the spor- 

 angium-wall, which open externally, and either completely 

 perforate the flattened lobes of the sporangia or are continued 

 into the capillitium threads. Spores dull purple, strongly 

 spinulose, 10 to 13 /x diam. — Macbr. N. Am. Slime-Moulds, 

 83. Mucor spongiosus Leysser Fl. Hal., 305 (1783). Reti- 

 cularia alba Bull. Champ., 92, t. 326 (1791). Spumaria 

 Mucilago Pers. I.e. • S. comuta Schum. Enum. PI. Saek 1 ., ii. 195 

 (1803). 8. alba DC. Fl. Fr., ii. 261 (1805) ; Fr. Syst. Myc, 

 iii. 95 ; Rost. Mon., p. 191 ; Lister Mycetozoa, 104. Didy- 

 mium spumarioides Fr. I.e., 121 (1829). Diderma spumariae- 

 forme Wallr. Fl. Germ. Crypt., 374 (1833). 



Var. 1.— dictyospora Fr. in Arkiv. Bot., i. 66 (1903) : lime 

 crystals small, nodular ; capillitium irregular, pale ; spores 

 very dark, closely reticulated, 12 to 13 ^ diam. 



Var. 2. — solida Sturgis hi Colorado. Coll. Publ., Sci. Ser., 

 xii., 29 (1907) : aethalia pulvmate compact, 4 to 5 cm. 

 diam., lime crystals small, often nodular ; capillitium scanty, 

 colourless, irregular ; spores spinulose, 9 to 11 fx diam. 



PI. 117. — a. aethalium (England) ; b. cluster of sporangia from an aethalium ; 

 in three places they are broken and show hollow columellae ; c. capillitium and spores, 

 with crystals from the outer covering of lime ; d. spore ; e. spore of var. dictyospora. 



This species is closely allied to Didymium crustaceum, but is dis- 

 tinguished by its aethalioid habit. In some seasons the cream-yellow 

 Plasmodium and large greyish-white aethalia form conspicuous features 

 about the blades and stalks of grass in pastures, especially in autumn. 

 The var. dictyospora was first gathered by Dr. R. E. Fries in Bolivia ; 

 it has since been found in some abundance in company with the typical 

 form about old straw heaps in Bedfordshire ; the aethalia are more 

 compact than in the type, and in the field are not always easily distin- 

 guishable from those of Fidigo cinerea. The var. solida is a still 

 more massive form ; it has been recorded hitherto from the State of 

 Colorado only. 



Hab. On grass, dead leaves, etc., common in Europe and the United 

 States.— Highgate, Middlesex (B.M. 161); Bedfordshire (B.M. 2514); 

 Oxfordshire (B.M. 1083); Somerset (B.M. 171); Cromarty (B.M. 

 1088) ; Ireland (K. 584) ; France (B.M. 997) ; Belgium (B.M. 594) ; 



