DIDYMIUM 113 



markable for the variations which it presents in the fruiting phase. 

 The hypothallus, sometimes entirely wanting, is anon well developed, 

 even continuous, venulose, from stipe to stipe. The capillitium varies 

 much in abundance as in color; when scanty, it is colorless and in every 

 way more delicate, when abundant, darker in color and sometimes 

 with conspicuous thickenings. 



D.fuckelianum Rost., as shown in N. A. F. 2090, and in some private 

 collections, seems to be a rather stout phase of this species; the stipe 

 is more abundantly and deeply plicate, is sometimes tinged with brown, 

 and the capillitium is darker colored and coarser than in what is here 

 regarded as the type of the species; but withal the specimens certainly 

 fail to meet the requirements of Rostafinski's elaborate description 

 and figure (Mon. 161, fig. 134). 



D. ejfusum Link probably stands for a sessile form of this species, 

 but Link's brief description is antedated by the much better one of 

 Albertini and Schweinitz. 



Nicaragua specimens not only show a continuous vein-like hypo- 

 thallus, but have the peridia often confluent, the columellae in such 

 cases confluent, the stipes distinct. Furthermore, the largest spores 

 reach the limit of 12.5 /*, and perhaps the larger number range from 

 10-12.5 ju, and all are very rough. This corresponds with D. macrosper- 

 mum Rost., which is distinguished, says the author (Mon., p. 162), 

 "chiefly by the large and strongly spinulose spores." However, the 

 same sporangia in our Central American specimens yield spores 9.5- 

 12.5 ix, a remarkable range, so that D. macrospermum, on this side 

 of the ocean, at least, cannot be distinguished from D. squamulosum, 

 so far as spores are concerned. A similar remark may be made rela- 

 tive to the form of the columella which Rostafinski, in his figures 

 especially, would make diagnostic. The columella in the sporan- 

 gium with largest and roughest spores is that of a perfectly normal 

 D. squamulosum. 



Cosmopolitan. Generally distributed throughout the wooded regions 

 of North America, from New England to Nicaragua, and from Canada 

 to California, West Indies, Bolivia, Brazil, Argentina. Not uncom- 

 mon about stable-manure heaps, in flower beds, and on richly manured 

 lands. 



Var. daviforme Sturgis, Colo. Coll. Pub. Sc. 12 : 27, 1907 (= D. an- 

 nulatum Macbr., N. A. Slime-Moulds ed. 2. 125. 1922) is a small 

 delicate phase, 0.4-0.6 mm. in diameter, with a deeply umbilicate or 

 annulate sporangium and a reduced columella. The spores are slightly 

 smaller than in the typical form, 8-10 {x, and the clustered spines more 

 noticeable. While at times it seems quite distinct, it is perhaps too 



