DIDYMIUM 91 



he thought it more appropriate. Fries describes the colu- 

 mella "none or black." I am in doubt whether we have the 

 typical Friesian form on this continent. The fructification is 

 in our specimens small, about 4 mm., and the spores, as note 

 by Morgan, small ; otherwise the species is hardly more than a 

 variety of the next. Under the name D. nigripcs Lister groups 

 our Nos. 8, 9, 10. N. A. F., 1393, represents Dr. Rex's concep- 

 tion of the present species. 



Not common. New York, Ohio, Iowa. 



9. DIDYMIUM XANTHOPUS (Ditmar) Fries. 



PLATE XVI., Fig. 10. 



1817. Cionium xanthopus Ditmar, Sturm, Deutsch. Fl., III., p. 37, t. 43. 

 1829. Didymium xanthopus (Dit.) Fries, Syst. Myc., III., p. 120. 

 1873. Didymium proximum B. and C., Grev., II., p. 52. 

 1892. Didymium microcarpon (Fries) Rost., Macbr., Bull. Lat. Nat. 

 Hist. Iowa, II., p. 146, (in part). 



1894. Didymium nigripes Fries, Lister, Mycetozoa, p. 98, (in part). 



Sporangia gregarious, white, globose, slightly umbilicate, stipi- 

 tate ; the peridium thin, and nearly or quite colorless, frosted 

 with crystals of lime ; the stipe yellowish or yellowish brown, 

 corneous, erect, subulate, slender ; hypothallus none ; columella 

 pale or white, turbinate, globose or depressed globose ; capillit- 

 ium of dull brown, or colorless threads more or less branched, 

 always white at the tips ; spores violaceous, nearly smooth, 

 7.5-8.5 /*. 



This seems to be the most common form in the United States. 

 It is distinguished from the preceding by the longer, more 

 delicate, generally orange-yellow, stem with pale or white colu- 

 mella. The spores also average a shade larger. N. A. F., 412 

 and 2089, are illustrations of D. xanthopus. The columella in 

 blown-out specimens is very striking, well confirming the diag- 

 nosis of Fries, " valde prominens, globosa, stipitata, alba." 

 Berkeley makes the color of the capillitium diagnostic of D. 

 proximum, but this feature is insufficient. 



Eastern United States ; common. 



