96 THE NORTH AMERICAN SLIME-MOULDS 



sideration in this connection. C. calcareum remains as applica- 

 ble to American forms having the spores 10-12 /u,, but according 

 to the author of the species the capillitium is abundant and 

 definitive. Unhappily the type of C. calcareuni is lost (Lister, 

 J//r., p. 95), so that there is no other means of verification 

 than the description and Rostafinski's figure. Under these 

 circumstances we consider the name calcareum inapplicable to 

 any American forms we have so far seen. See next species. 

 As to the American species which have been distributed as 



C. calcareum (Lk.) Rost, they are, so far as seen, referable to 



D. reticulatum (Rost.), Morg. Here also belongs No. 1217, 

 Ellis, N. A. F. 



New York, Pennsylvania, Ohio, Iowa, Nebraska. Probably 

 to be found throughout the eastern United States. 



3. DIDERMA PERSOONII Macbr. nom. nov. 



1894. Diderma difforme Pers., Morg., Jour. Cin. Sac., p. 70. 



Sporangia sessile, gregarious or closely aggregate, depressed, 

 roundish, elliptical, elongate or plasmodiocarpous as in the pre- 

 ceding species ; outer peridium pure white, smooth, fragile, 

 remote from the inner, which is thin, ashen, or bluish, and 

 inclined to iridescence ; columella alutaceous or brownish, not 

 distinguishable from the base of the fructification, the so-called 

 hypothallus ; capillitium very scanty, short and nearly color- 

 less, simple or slightly forked; spores violet brown, smooth, 

 10-12.5 //.. 



This species resembles in general character some phases of 

 the preceding. It is, however, more brilliantly white, and the 

 inner peridium in good specimens shows a peculiar lustre of a 

 coppery tinge unlike anything else. The spores also are im- 

 mediately diagnostic, large, nearly smooth, dark purple brown 

 in color. According to Rostafinski's description and figures, 

 it can hardly be referred to the lost D. calcarcnm. D. difforme 

 Pers. has been removed from the genus. See under No. 2, 

 preceding. It is pleasant, in the specific name suggested, to 

 commemorate the name of the author of the genus. 



