222 A Monograph of the Erysiphaceae 



Univ. ;53, 754, *EII. & Everh. Fung. Columb. 222 ; Ell. & 

 Everh. N. Amer. Fung. 2763. 



Amphigenous ; mycelium evanescent or here and there per- 

 sistent, at first white becoming yellowish, perithecia more or less 

 densely gregarious, sometimes very crowded and forming a crust- 

 hke covering, globose-depressed, variable in size, 130-230 /i in 

 diameter, usually about 180 /^; cells 10-15 /^ wide, usually \o fi, 

 often obscure; appendages numerous, densely interwoven, from 

 equaling to 2-4 times exceeding the diameter of the perithecium, 

 colorless or rarely pale yellowish-brown in the lower half, more 

 or less branched, irregularly swollen and bent at intervals, at first 

 thui-walled and septate, becoming thick-walled towards base; 

 asci numerous, usually about 20, but sometimes as many as 42, 

 from ovate-oblong to more or less cylindrical, large, 80-115 x' 

 30-40 n ■ spores 8, rarely 7, very rarely 6, somewhat roundish, 

 16-20 X 10-15 !i, usually about 18 x 12 /i. 



Host— On female catkins of alder ; Almis incana, A. serru- 

 lata, A. viridis. 



Distribution.— ^Q^T^i America : United States— New Hamp- 

 shire, Massachusetts. New York, New Jersey, Pennsylvania, 

 Canada, New Brunswick, Ontario. 



Peck (279, p. 63) originally published the present species as 

 the type of a new genus, with the following description : '< Ery- 

 siphella nov. gen., perithecia destitute of appendages, spores def- 

 inite. This genus differs from Perisporium in having a definite 

 number of spores In an ascus, and from Uncinula, 

 and Erysiphc in being destitute of appendages." 



The present species really possesses, ho^'wever, as Farlow (123) 

 has already pointed out, very numerous appendages, and is cer- 

 tainly to be referred to the genus Erysiphe. The appendages are 

 more or less densely Interwoven, forming usually a pulvinate mass 

 at the base of the perithecium, and are somewhat easily broken 

 ofiC so that often on quite old perithecia only the broken ends are 

 to be found, or sometimes even these are not to be seen 



Although distinct in its curious habitat on the female catkins of 

 aiders, E aggrcgata morphologically must be considered very 

 close to E polygoni, from which It differs only in the large peri- 

 thecia, and larger, more numerous, subcylindrical asci. The eight 

 roundish spores give a characteristic appearance at first sight to E 

 aggregata, but just the same shaped spores are found in the in- 



Mia 



