236 A Monograph of the Myxogastres. 



Didymimn effusum, Rost. b-sqoo 



Sporangia densely aggregated or scattered, sessile on a broad 

 base, circular or irregular in outline, depressed, wall grey, pruinose 

 with numerous minute crystals aggregated in masses; columella 

 hemispherical, white or pallid, rugulose ; threads of capillitium 

 very slender, colourless or pale fuliginous, furnished with scat- 

 tered coloured protuberances, combined to form an irregular dense 

 net; spores globose, brownish-purple, minutely warted, 10 12 jx 

 diameter. 



Didymium effusum,, Rost, Mon., p. 163 ; Sacc., Syll., no. 1302. 



On leaves, wood, &c. Britain (Cornwall) ; Finland ; Sweden ; 

 France; Germany; United States; Ceylon. 



About '5 mm. diameter, characterized by the white columella, 

 the capillitium threads furnished with numerous well-defined 

 projections in the form of thickened plates or pyriform swellings, 

 and the dense meal of crystals on the wall. 



(Rostafmski's Synonyms.) 



D&crma effusum, Link, Obs. I, p. 42 (1809). 

 Didymium effusum, Fr., 1. c., in., p. 124 (1829). 

 Physarum conftuens, Fr., Excl. Syn., 1. c., iii., p. 146 (1829). 



Sub- Gen. Hemididymium. 



Capillitium usually dense, threads branching and anastomosing 

 to form an irregular network throughout the capillitium, angles 

 usually flattened and more or less triangular. 



The species included in 'the present sub-genus are distin- 

 guished from those belonging to the sub-genus Didymium by 

 the absence of the simple or bifurcating threads at the basal 

 portion of the capillitium. 



A. Sporangium stipitate. 



* Spores smooth. 

 Didymium longipes, Mass. (n. sp.) (fig. 226). P^ ' 



Sporangia small, globose, snow-white, frosted with a few 

 scattered granules or crystals of lime; stem very long and 



