98 THE NORTH AMERICAN SLIME-MOULDS 



wall smooth, polished, crustaceous, fragile, far remote from the 

 inner, which is thin, smooth, or rugulose, iridescent blue ; hypo- 

 thallus usually pronounced and spreading beyond the sporangia, 

 sometimes scanty or lacking ; columella variable, sometimes 

 very small, inconspicuous, sometimes large, globose, ellipsoidal, 

 even pedicellate ; capillitium abundant, brown or purplish 

 brown, branching and occasionally anastomosing to form a 

 loosely constructed superficial net ; spores globose, delicately 

 spinulose, 8 /u-. 



This species seems rare in this country. The only specimens 

 so far are from Iowa. It is distinguished by small spores and 

 general snow white color. Lister has thrown doubt upon Rosta- 



A 



finski's definition of this form Mycetozoa, p. 78. Almost every- 

 thing distributed in the United States under this name belongs 

 in the next species. Reported also from Ohio Morgan. 



6. DlDERMA CRUSTACEUM Peck. 



PLATE VII., Fig. 7. 



1871. Diderma crustaceum Peck, Rep. N. Y. Afus., XXVI., p. 74. 

 1889. Chondrioderma crustaceum (Peck) Berl., Sacc., VII., p. 373. 



Sporangia closely crowded or superimposed, in a cushion- 

 like colony, creamy white, globose, imbedded in the substance 

 of the hypothallus, the outer peridium smooth, delicate, crusta- 

 ceous, fragile, remote from the blue iridescent inner membrane ; 

 hypothallus prominent; columella variable, generally present, 

 globose ; capillitium dark colored, the threads branching and 

 combining to form a loose net ; spore-mass black, spores by 

 transmitted light dark violaceous, delicately roughened, 12-15 /" 



Common. Readily to be distinguished from the preceding 

 by the larger spores and more crowded habit. New England 

 west to Nebraska. 



The Didermas are generally delicately beautiful. The outer 

 wall in the present species is like finest unglazed china, softly 

 smooth, and yet not polished, often absolutely white, with porce- 

 lanous fracture. An inter-parietal space separates the outer 

 from the inner wall, so that the former may be broken, bit by 



