Fructification wholly plasmodiocarpous, snow-white, small, 2-6 mm., flat and thin; the outer wall double, membranous within, calcareous-crystalline without; columella none; capillitium simple of rather thick, vertical, brown threads, sparingly united laterally, and only occasionally furcate at the ends, especially above; spores minutely spinulescent, violaceous pale, 12-15 µ.
Massee thought English specimens out of harmony with the original description and gave them a new name. To refuse this, Lister enlarges the range of spore-measurements and disregards some of Rostafinski's specifications as to capillitium. Our specimens are as described.
Bohemia. England. Shores of Lake Okoboji, Iowa.
This is indeed a doubtful form. It differs from _D. difforme_ chiefly in that the outer calcareous shell is not smooth, but is covered with abundant loose crystals, frosted. The spores are paler but about the same size. The frosting may be incident to local climatic conditions at the time and place of desiccation.
1797. _Diderma difforme_ Pers. _Tentamen Disp. Meth._, p. 19. 1830. _Didymium difforme_ Duby., _Bot. Gall._, ii., p. 858. 1875. _Chondrioderma difforme_ Pers., Rost., _Mon._, p. 177. 1894. _Didymium difforme_ Duby., List., _Mycetozoa_, p. 94. 1899. _Diderma personii_ Macbr., _N. A. S._, p. 96. 1911. _Didymium difforme_ Duby., List., _Mycetozoa, 2nd ed._, p. 124.
Plasmodiocarpous, the smooth, white outer peridium separable from the thin, colorless or purplish inner layer; capillitium of rather coarse, flat, dichotomously branching threads, broader below; spores minutely warted, or almost smooth, dark brown, 12-14 µ.
The white crust-like outer wall has more than once carried this species into _Diderma_. It is still doubtful whether we are here dealing with _Chondrioderma calcareum_ Rost. Miss Lister cites a variety, _S. difforme comatum_, with more abundant capillitium which may represent Rostafinski's species.
Evidently rare in the United States; reported more common in Europe and eastward. In our specimens the crust-like outer peridium shows crystals on the broken edge only; the body of the object, as its outer surface seems to be amorphous.
1895. _Chondrioderma quitense_ Pat., _Bull. Soc. Myc. Fr._, XI., p. 212. 1909. _Didymium quitense_ (Pat.) Torr., _Flor. Myxom._, p. 150. 1911. _Didymium quitense_ Torr., List., _Mycetozoa, 2nd ed._, p. 126. 1913. _Didymium quitense_ (Pat.) Torr., Sturg., _Myx._, Col. II., p. 446.