DIDYMIUM 87 



Rostafinski (by typographical error ?) confused in the Mono- 

 graph, pp. 164, 165, this species with Persoon's Physarum conflit- 

 ens. 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. 



4. DIDYMIUM SQUAMULOSUM (Alb. and Schw^) Fries. 



1805. Diderma squamnlosum Alb. and. Schw., Consp. Fung., p. 88. 



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



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

 p. 118. 



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



1894. Didymium effusum (Link) Lister, 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 ; hypothal- 

 lus small or obsolete ; capillitium of delicate branching threads, 

 usually colorless or pallid, sometimes with conspicuous calci- 

 form thickenings ; spores violaceous, minutely warted or spinu- 

 lose, 8-10 /i. 



This, one of the most beautiful species in the whole series, is 

 remarkable for the variations which it presents in the fruiting 

 phase. These range all the way from the simplest and plainest 

 kind of a plasm odiocarp with only the most delicate frosting of 

 calcareous crystals up through more or less confluent sessile spo- 

 rangia to well-defined elegantly stipitate, globose fruits, where the 

 lime is sometimes so abundant as to form deciduous flaky scales. 

 The hypothallus, sometimes entirely wanting, is sometimes 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 stronger thickenings. 



D.fuckeliannm Rost., as shown in N. A. F., 2090, and in 

 some private collections, seems to be a rather stout phase of the 



