110 A Monograph of the Erysiphaceae 



North America : (on Tilia) United States : New York, Mary- 

 land, Ohio, Michigan, Indiana, Illinois, Wisconsin, Iowa, Minnesota. 

 Canada — Ontario. 



This species shows great affinity with the European U. pnt- 

 iiastri, from which it differs in the usually fewer and always broader 

 asci, larger spores, and usually more swollen apex of the append- 

 ages. With regard to the last character, however, there is cer- 

 tainly much variation, as a glance at Fig. 8 1 will show, and it 

 would be unsafe to place any great value on this point. 



U. Clintonii has been hitherto regarded as confined to North 

 America, where it occurs not unfrequently on the single host-plant, 

 Tilia Americana. Among the Japanese specimens of Erysiphaceae, 

 however, sent to me by Professor :Miyabe there occurs an Uitcinula, 

 which, although differing slightly from the American examples 

 must, I think, be included under the present species. Two speci- 

 mens were sent, one on Zdkova acuminata (Z. Keaki) from Kobe, 

 (K. Miyabe, Aug. 1889), the other on Aphananthe aspera from 

 Tokyo (K. Sengoku, Oct. 1898). 



The first specimen sent was that on Zdkova, and as this differed 

 in several characters from the American form, I was at first in- 

 clined to rank it as a variety minor under U. Clintonii. The speci- 

 mens showed these characters : mycelium epiphyllous, subpersis- 

 tent, very thin, effused; perithecia uniformly scattered over the 

 upper surface of the leaf, small, 64-86/^ in diameter, averaging 

 78/^, cells 10-20 /i wide; appendages 12-25, unequal in length, 

 from equalling to twice exceeding the diameter of the perithecium, 

 colorless, simple, thick-walled, refractive and narrow (about 4, « 

 wide) at the base, thin-walled and enlarged upwards, about 20 « 

 wide across the simply uncinate apex ; asci 2-4, usually 3, 40-50 



3-5, crowded in the ascus, 20-24 x 



very 



o- 



This "var. minor" could be thus contrasted with the American 

 plant: U. Clintonii (American); perithecia 80-130// in diameter, 

 appendages 22-30/^ wide across the apex, asci 4-10. "Var. 

 mijior'' (Japanese); perithecia 64-86/^ in diameter, appendages 

 about 20// wide across the apex, asci 2-4, usually 3. 



The second Japanese specimen sent (on Aphananthe), however, 

 broke down these distinctions, as this form has perithecia 75- 



