90 THE NORTH AMERICAN SLIME-MOULDS 



7. DIDYMIUM CLAVUS (Alb. and Schw.} Rabcnhorst. 



1805. Physarnm davits Alb. and Schw., Consp. Fung., p. 96. 



1829. Didyminm melanopus Fries, Syst. Myc., III., p. 114. 



1844. Didyminm clavus (Alb. and Schw.) Rabh., Ger. Cr. Fl., No. 2282. 



Sporangia gregarious, pale gray, discoid or piliate, depressed 

 stipitate ; the peridium dark-colored, frosted with calcareous 

 crystals above, naked below ; stipe short, slender, tapering 

 upward, furrowed, arising from a hypothallus more or less dis- 

 tinct, black ; columella obsolete ; capillitium of delicate threads, 

 pale or colorless, little branched ; spores violaceous, pale, nearly 

 smooth, 6-8 /A. 



This species is well differentiated, easy of recognition by 

 reason of its peculiar discoid sporangium, calcareous above, 

 naked and black beneath. D. ncglcctum Massee, reported from 

 Philadelphia, is said to be a slender form of the present species. 

 The figures of D. davits by Albertini and Schweinitz are excel- 

 lent, as also the description. 



Not common. Pennsylvania, Ohio, Iowa. 



8. DIDYMIUM NIGRIPES (Link} Fries. 



PLATE VII., Figs. 2, 2 a, 2 b. 



1809. Physarum nigripes Link, Obs. Diss., I., p. 27. 



1818. Physarum microcarpon Fries, Sym. Cast., p. 23. 



1829. Didymium nigripes (Link) Fries, Syst. Myc., III., p. 119. 



1875. Didymium microcarpon (Fries) Rost., Mon., p. 157. 



1896. Didyminm microcarpum Fries, Morg., Jour. Cin. Sac., p. 61. 



Sporangia gregarious, globose or hemispheric, umbilicate be- 

 neath, small, white, stipitate; the peridium smoky, covered with 

 minute calcareous crystals ; stipe slender, erect, black, opaque ; 

 hypothallus scutate, black ; columella distinct, globose, black or 

 dark brown ; capillitium of delicate threads, pale brown or color- 

 less, with occasional brown thickenings or nodes, sparingly 

 branched ; spores pale, violaceous by transmitted light, minutely 

 warted, 6-8 /*. 



This is D. microcarpon Rost. Fries (Syst. Myc., III., 119) 

 acknowledges the priority of Link's appellation, and discards 

 microcarpon. Rostafinski adopted microcarpon simply because 



