DSDERMA 95 



2. DIDERMA RETICULATUM (Rest.) Morgan. 



PLATE XVI., Fig. n. 



1875. Chondrioderma reticulatum Rost, Man., p. 170. 



1894. Diderma reticulatum (Rost.) Morg.,/our. Cin. Sac., p. 71. 



Sporangia gregarious, generally rounded and much de- 

 pressed, flat, sometimes, especially toward the margin of a 

 colony, elongate, venulose or somewhat plasmodiocarpous, dull 

 white, the inner peridium ashen or bluish, remote from the 

 calcareous crust, which is extremely fragile, easily shelling off ; 

 columella indistinguishable from the base of the sporangium, 

 thin, alutaceous ; capillitium of short, generally colorless, deli- 

 cate, sparingly branching or anastomosing threads perpendicu- 

 lar to the columella ; spores black in mass, by transmitted light 

 violet tinted, smooth, 6-8 p. 



Perhaps our most common species. Found in fall on dead 

 twigs, leaves, etc. Recognized by its rather large, white, de- 

 pressed or flattened sporangia tending to form reticulations, 

 and hence suggesting the name. The lines of fruiting tend to 

 follow the venation of the supporting leaf ; where the sporan- 

 gium is round, the columella is a distinct rounded or cake-like 

 body ; where the fruit is venulose, the columella is less distinct. 



Rostafinski divided the genus CJiondrioderma, i.e. Diderma, 

 into three sections : 



Monoderma to include those species in which the calcareous 

 crust is less distinct or connate with the true peridium. 



Diderma, in which the two structures were plainly separate. 



Leangium, used as in the present work. In his first section 

 Rostafinski placed C. reticulatum and C. michclii ; in the second, 

 C. difforme and C. calcarcnm. 



Lister has examined Rostafinski's type of C. reticulatum and 

 declares that it has the usual Didermic characters. Hence 

 there is no doubt that our small-spored American specimens 

 are covered by Rostafinski's description, No. 72. On the other 

 hand, Lister makes C. difforme (Pers.) Rost. a Didyminm, by its 

 crystalline coat. That species therefore is removed from con- 



