DIDERMA 129 



10. Diderma niveum (Rost.) Macbr. 



N. A. Slime-Moulds 100. 1899. 

 PI. IX, Figs. 192, 193. 



1829. Diderma deplanatum Fr., Syst. Myc. 3 : 110. 



1849. Leocarpus deplanatus Fr., Summ. Veg. Scand. 450. 



1875. Chondrioderma niveum Rost., Mon. 170. 



1875. Chondrioderma physaroides Rost., Mon. 170. 



1876. Chondrioderma deplanatum (Fr.) Rost., Mon. App. 17. 



1877. Diderma albescens Phill., Grev. 5 : 114. 



1892. Chondrioderma albescens (Phill.) Massee, Mon. 209. 



Sporangia gregarious, scattered, or more often crowded, sessile, 

 depressed-spherical, sometimes ellipsoidal or elongate, white, the 

 outer peridium crustaceous, chalky, smooth and fragile, the inner dis- 

 tinct, delicate, ochraceous; hypothallus scant or none; columella well 

 developed, globose or hemispherical, orange-tinted or ochraceous; cap- 

 illitium abundant, made of threads of two sorts, some purplish or 

 dusky, with pale extremities, uneven, others more delicate and color- 

 less, and with wart-like thickenings, all sparingly branched; spores 

 violet-brown, minutely roughened, 9-13 /x. 



This species is not common. From Colorado we have fine specimens 

 typical in every way. Specimens from Washington are flatter, and may 

 represent D. deplanatum Fr. In the Mycetozoa ed. 3. 90, Miss Lister 

 treats this as a distinct species, distinguishing it from D. niveum by its 

 plasmodiocarpous habit and absence of columella. But in the descrip- 

 tion it is stated "Columella hardly developed or broadly convex, 

 orange" which seems to leave the distinction uncertain, to say the 

 least. Furthermore, in the American collections there is no correlation 

 between the small spores and the flattened columella, the latter being 

 rather associated merely with the plasmodiocarpous phase. This is 

 less true of the European collections at hand, but most of them are 

 obviously incomplete developments, with many giant and imperfectly 

 matured spores. If the two species are finally proved to be identical, 

 Fries' name must take precedence. Pending such final proof, we retain 

 the more familiar name. 



Colorado, Washington, Oregon, California; Europe. 



Diderma microcarpum Meylan (Bull. Soc. Vaud. Sc. Nat. 55 : 240, 

 1924) is certainly very close to the preceding species, although the 

 author regards it as distinct. The sporangia are smaller, 0.3-1 mm. in 

 diameter, the peridial layers rarely separated, the spores 10-1 1 /x. 



