I, so Cincinnati Society of Natural History. 



pacted, the branches running out into numerous free-pointed 

 extremities. Capillitium of rather thick threads, forming a 

 dense net, with Inroad expansions at the angles. Spores 11-14 

 mic. in diameter. This is Spumaria cornuta, Schum. It is 

 evidently the form so elaborately figured by Rostafinski, and 

 which Fries says abounds in Northern Europe. 



Var. 3. MUCiLAGO. .-Ethalium large, even and uniform in 

 outline, covered by a thick, white, common cortex ; the spo- 

 rangia laterally confluent and densely compacted together 

 throughout. Capillitium of rather slender threads, forming a 

 loose net, scarcely expanded at the angles. Spores 10-13 

 mic. in diameter. This is Spumaria inncilago, Nees, as figured 

 by Greville in the Scottish Cryptogamic Flora. The capil- 

 litium is figured by McBride in The Myxomycetes of Iowa. 

 This is the only form I have metwith in this country. 



III. DIDERMA, Pers. Sporangia subglobose and stipitate 

 or more often sessile, sometimes plasmodiocarp ; the wall a 

 thin membrane, with an outer layer composed of minute 

 roundish granules of lime, which are usually compacted into 

 a smooth continuous crust. Stipe present or mostly absent ; 

 the columella usually well developed. Capillitium of very 

 slender threads, stretching from the columella to the wall of 

 the sporangium, more or less branched, and combined into a 

 loose net by short lateral branchlets. Spores globose, viola- 

 ceous. 



This genus is easily recognized by the smooth crustaceous 

 layer of lime on the outer surface of the sporangium : in 

 many cases this easily shells off" or breaks away. Such a 

 coating occurs in a few species of Physarum, but here the 

 vesicles of lime attached to the threads distinguish them. 

 This is Chondrioderma of Rostafinski's monograph; the 

 reason for coining a new name and entirely discarding the old 

 one is not apparent. 



§1. Leangium. Sporangium usually stipitate ; the wall at 

 maturity separating from the inner mass of spores and capilli- 

 tium and splitting iu a stellate manner, the segments becom- 

 ing reflexed. 



