DIDERMA 123 



broadly effused mass; outer peridium a thin, white, calcareous crust 

 closely applied to the delicate membranous and colorless inner wall; 

 columella thin, alutaceous, scarcely more than a base of the plasmodio- 

 carp; capillitium pale, consisting of short threads somewhat branched 

 toward their distal extremities; spores faintly echinulate, with a few 

 clusters of darker and larger, but still minute spines, 7-9 li. 



The two layers of the peridium are sometimes scarcely distinguish- 

 able, the outer a thin, crustose shell closely applied to the membranous 

 inner wall. 



New York, Ohio, Nebraska, Argentina; apparently rare in America. 

 Widespread in the old world and said to be not infrequent in the 

 British Isles. Africa, East Indies, Japan. 



Var. reticulatum (Rost.) Macbride, N. A. Slime-Moulds ed. 2. 131, 

 1922 (= Didymium reticulatum Rost., in Fuckel, Symb. Myc. Nachtr. 

 73, 1873; Chondrioderma reticulatum Rost., Mon. 170, 1875; Diderma 

 reticulatum (Rost.) Morg., Jour. Cin. Soc. Nat. Hist. 16 : 155, 1894). 

 Sporangia gregarious, generally rounded, not much depressed, flat, 

 sometimes, especially toward the margin of a colony, elongate, venu- 

 lose or somewhat plasmodiocarpous, dull white, the inner peridium 

 ashen or bluish, remote from the calcareous crust, which is extremely 

 fragile, easily shelling off; columella indistinguishable from the base 

 of the sporangium, thin, alutaceous; capillitium of short, generally 

 colorless, delicate, sparingly branching or anastomosing threads per- 

 pendicular to the columella; spores black in mass, by transmitted 

 light violet-tinted, nearly smooth, with a few shadows marking clusters 

 of minute spines, 7-9 ix. 



Perhaps our most common form. Found in fall on dead twigs, 

 leaves, etc. Recognized by its rather large, white, depressed or flat- 

 tened sporangia tending to form reticulations, and hence suggesting 

 the name. The lines of fruiting tend to follow the venation of the 

 supporting leaf; where the sporangium is round, the columella is a 

 distinct rounded or cake-like body; where the fruit is venulose, the 

 columella is less distinct. 



New York, Pennsylvania, Ohio, Wisconsin, Iowa, Nebraska, probably 

 throughout the eastern United States, Brazil; Europe, Ceylon, Java. 



2. Diderma alpinum Meylan 



Bull. Soc. Vaud. Sc. Nat. 51 : 261. 1917. 



1913. Diderma globosum Pers. var. alpinum Meylan. Ann. Cons. Bot. Geneve 



310. 

 Plasmodiocarpous or sporangiate, the plasmodiocarps short, the 

 sporangia sessile and crowded on a plasmodiocarp-like hypothallus, 



