146 Cincinnati Society of Natural History. 



sporangium rarely absent. It is considered by Lister to be a 

 variety of D. farinaceian ; it differs from this species in its 

 smaller and less-depressed sporangium and in its smaller 

 nearly smooth spores. 



B. Sporangia sessile. 



6. DiDYMiUM EFFUSUM, Link. Sporangia gregarious or 

 scattered, sessile on a flattened base, convex above, various in 

 shape, subrotund or by confluence effused and venosely creep- 

 ing; the wall very thin and pellucid, invested with a thin 

 flocculose layer of minute crystals of lime. The columella 

 hemispheric, rugulose, usually snow-white. Capillitium of 

 very slender colorless threads, furnished with numerous 

 minute protuberances, much branched and combined into a 

 dense net. Spores globose, very minutely warted, dark viola- 

 ceous, lo-ii mic. in diameter. 



Growing on old leaves, wood, etc. Sporangium about .5 

 mm. in diameter or thickness, sometimes confluent and more 

 or less elongated as a plasmodiocarp. This species is reported 

 from the United States, but I have seen no specimens. 



7. DiDVMiUM PHYS.\ROiDEvS, Pers. Sporangia roundish or 

 hemispheric, more or less irregular and deformed, sessile or 

 with a very short stipe, and closely crowded together upon a 

 strongly-developed common hypothallus ; the wall a dark 

 colored membrane, with a thin layer of stellate crystals of 

 lime. The columella large and thick, divided into cells which 

 are filled with irregular lumps of lime, common to all the 

 sporangia. Capillitium of stout threads, usually simple, only 

 rarely branched, furnished with numerous fusiform swellings. 

 Spores globose, minutely warted, dark violaceous, 12-14 mic. 

 in diameter. 



Growing on old wood, bark, moss, etc. Reported from 

 Carolina by Curtis. It is said superficially to resemble some- 

 what Physarum didermoides. 



*^2. Pl.vcenti.v. Columella basal, much depressed, very 

 thin or quite obsolete, connate with the base of the sporan- 

 gium; the threads of the capillitium ascending to the wall of 

 the sporangium. 



