DIDYMIUM 109 



species is so different from other didymiums that it may have to be 

 placed in a distinct genus. Pending further study it seems unnecessary 

 to rename it. 



Rare. Iowa, Montana, Colorado, Pennsylvania; England. 



6. Didymium anellus Morgan 



Jour. Cin. Soc. Nat. Hist. 16 : 148. 1894. 

 PI. VIII, Figs. 156, 157, 158. 



Plasmodiocarp in small rings or links, often confluent and elongated, 

 irregularly connected, bent and flexuous, resting on a thin venulose 

 hypothallus, or sometimes globose, the peridium dark colored, with a 

 thin layer of stellate crystals, dehiscing in more or less circumscissile 

 fashion; capillitium of slender, dark colored threads, which extend 

 from base to wall, more or less branched, and combined into a loose 

 net; columella a thin layer of brown scales; spores globose, very 

 minutely warted, violaceous, 7-10 /jl. 



This minute species resembles a poorly developed, or sessile, phase 

 of D. melanospermum. Some of the fructifications are spherical; such 

 may show a very short dark stalk. The columella is usually lacking 

 and the spores are much smaller than those of D. melanospermum. 

 The original description reads "irregularly dehiscent." The tendency 

 toward a circumscissile dehiscence, referred to in the English mono- 

 graph, is apparent in specimens collected by the author of the species 

 in Ohio in 1893. 



Ohio, Iowa, Colorado, New Mexico, California; Europe, southern 

 Asia. 



7. Didymium dubium Rost. 



Mon. 152. 1875. 

 1908. Didymium wilczekii Meylan, Bull. Soc. Vaud. Sc. Nat. 44 : 290. 



Fructification plasmodiocarpous, white or grayish white, flat and 

 thin, 2-16 mm. long and up to 6 mm. wide; peridium double, the 

 outer layer composed of rather loosely compacted crystalline cal- 

 careous granules, the inner layer tough and membranous, tawny 

 plumbeous; columella scanty or none; capillitium of rather thick brown 

 threads vertically arranged, 270-300 n long, sparingly united laterally 

 and occasionally forking, especially above; spores dark violet, distinctly 

 warted, 11-14 fx. 



Mainly a mountain form. Small plasmodiocarps with firm shell- 

 like peridium and smaller and smoother spores collected in Iowa are 

 now referred to D. listeri. 



Colorado; Europe. 



