128 THE MYXOMYCETES 



lacking; columella white, variable, sometimes very small, inconspicu- 

 ous, 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, 7.5-10/*. 



As noted under D. crustaceum, Lister includes that species in the 

 present one and gives the spore measurements as 10-14 /i, rather a 

 wide range. But Rostafinski said 8.3 /*, the fraction indicating caution, 

 as though it were the average of several measurements. We do have 

 the small-spored form, although it is rare, and it may be what Rosta- 

 finski had in mind. In some of our material the spores attain 10 n and 

 the measurements are changed in accordance with this conception of 

 the species. 



Rare. Ohio, Wisconsin, Iowa, Washington; Hungary, Rumania, 



North Africa. 



9. Diderma lyallii (Massee) Macbr. 



N. A. Slime-Moulds 99. 1899. 

 PI. IX, Figs. 190, 191. 



1892. Chondrioderma lyallii Massee, Mon. 201. 



1911. Diderma niveutn (Rost.) Macbr. var. lyallii Lister, Mycetozoa ed. 2. 105. 



Sporangia obovate, more or less closely crowded, white, creamy or 

 pallid carneous, substipitate, about 1 mm. in diameter; outer peridium 

 firm, stout, encrusted, especially above, with granular masses of lime, 

 the inner well developed, close to the outer, more or less cartilaginous, 

 opaque, yellow or buff colored; hypothallus well developed, venulose, 

 white, passing up unchanged to form the short, stout stipe and lower 

 outer peridium; columella prominent, half the height of the sporan- 

 gium, flesh colored or brown; capillitium of short, brown threads, rigid, 

 much branched, forming a net, widened irregularly and especially at 

 the nodes; spore-mass black; spores by transmitted light dark brown, 

 rough, 14-17/1. 



A very distinct species, the large, fine, showy sporangia in more or 

 less crowded clusters springing from a snow-white, common hypo- 

 thallus. First reported from western Canada, it has since been found 

 throughout the region from the Rocky Mountains to the Pacific. 

 Meylan believes it should be grouped with the leangiums. Occasionally 

 the outer peridium is broken up into calcareous plates, as in Lepido- 

 derma. Specimens from Rumania, distributed by Brandza, No. 97, 

 show an extreme development of this tendency. 



Western United States and Canada, Chile; Europe. 



