DIDYMIUM 119 



bifid, or more than once di'chotomously divided ; spores strongly 

 warted, globose, violet-brown, 10-13 /x. 



This species has in some ways all the outward seeming of a 

 diderma, but cannot be referred to that genus because of the crystal- 

 line character of its crust. This is a very marked structure; loosely 

 built up of very large crystals, it is necessarily extremely frail, never- 

 theless persists, arching over at a considerable distance above the 

 peridium proper. Sometimes, however, caducous, evanescent. 



The sporangia are said to be sometimes stipitate. This feature 

 does not appear in any of the material before us. Lister in Myceto- 

 zoa PL XL., c. draws the capillitium much more delicate than it 

 appears in our specimens. The hypothallus is sometimes noticeable 

 under some of the sporangia where closely crowded, but is not a 

 constant feature. 



Rostafinski (by typographical error?) confused in the Monograph, 

 pp. 164, 165, this species with Persoon's Physarum confiuens. In 

 the Appendix he substitutes the Friesian nomenclature. Persoon's 

 description of his species is insufficient, and throws no light on the 

 problem whatever. 



Rare. Iowa; Black Hills, South Dakota. Reported common in 

 Europe. Canada; Vancouver Island to the St. Lawrence. 



6. DiDYMIUM SQUAMULOSUM (Alb. £j Schw.) Fries. 



1805. Diderma squamulosum Alb. & Schw., Consp. Fung., p. 88. 



1816. Didymium effusum Link, Diss., II., p. 42. 



1829. Didymium squamulosum (Alb. & Schw.), Fries, Syst. Myc, III., 

 p. 118. 



1875. Didymium effusum (Link) Rost., Mon., p. 163. 



1894. Didymium effusum (Link) List., Mycetozoa, p. 99. 



Sporangia, in typical forms, gregarious, globose or depressed- 

 globose, gray or snow-white, stipitate ; the peridium a thin iridescent 

 membrane covered more or less richly with minute crystals of lime; 

 the stipe when present, snow-white, fluted or channelled, stout, even ; 

 columella white, conspicuous; hypothallus usually small or obsolete; 

 capillitium of delicate branching threads, usually colorless or pallid, 

 sometimes with conspicuous calyciform thickenings ; spores violaceous, 

 minutely warted or spinulose, 8-10 ju. 



