Perithecia few or numerous, immersed in the mycelium, small 75-85 //, 

 globose or subpyriform ; appendages of two kinds, in part rudimentary, 

 floccose, deeply colored, attached in a broad tuft to the smaller end 

 of the pyriform perithecium, the others strongly developed, rigid, 

 straight or curved, continuous or septate, simple or rarely forked at 

 the extremity, deeply colored at base, becoming pale outwardly, 

 attached in a loose cluster opposite the rudimentary ones, 2-5 times 

 the diameter of the perithecium. Ascus oval to subglobose. Sporidia 

 8, 20-30 fji long. 



On upper parts of the twigs of Pyrus Mains, especially in nurs- 

 eries of young trees, and upon the suckers from old ones. Not appar- 

 ently very frequent but exceedingly abundant at times. Mississippi 

 Valley, and probably eastward. 



This exceedingly interesting species has not been well separated 

 from Podosphcera OxyacanthdB which occurs on the same host and to 

 casual observation has much the same appearance. In our species the 

 tips of the large appendages are occasionally forked (once or even 

 slightly twice), which again may have been confusing. But these 

 vague, stiff branches are totally unlike the diqhotomous divisions of 

 Podosphcera, and otherwise the species are very distinct. The tuft 

 of short, interwoven, rudimentary appendages, like a dense cluster of 

 short roots, is a very characteristic mark. 



There is still some doubt as to the name. Evidently Erysiphe 

 Mall, Moug. usuallv id von as a variety of Erysiphe adunca, (Frie^ 

 Syst. Myc. Ill, p. 245, Wallr. Flora" Germ. IV, p. 755, &c.) is a 

 different thing, but Duby's description (Botanicon Gallicuin I, p. 869) 

 so far as it goes, is sufficiently correct for our species. Erysiphe 

 Mali, Dubv, in Roumeguere's Finuj't. Gallici Exsiccati is a S}jhce- 

 rotheca, and seems to be the same as our plant, though the specimen 

 examined was insufficient for satisfactory comparison. It is moreover 

 scarcely possible that this host should have a solely American parasite 

 of this kind upon it, hence the preference given in the nomenclature. 



S. mors-iivse, (Schw.) 



Erysiphe mors-uvtz, Schw. Syn. N. Am. 2494. 

 Sphczrotheca mors-uvtz, B. & C. Grevillea IV, p. 158. 



Mycelium abundant, at first white, becoming dark brown, densely 

 covering the leaves, stems and fruit. Perithecia most abundant on 

 the stems and fruit, densely aggregated, imbedded in the thick, felted 

 mycelium, variable in size, 19-120 //, dark brown, reticulations 

 obscure; appendages short, delicate, hyaline or slightly colored, 

 interwoven with and overrun by the dense mycelium. Ascus broadly 

 elliptical, S-spored, both ascus and sporidia smaller than in S. 

 nosa. 



