134 ■ A Monograph of the Erysiphaceae 



Distribution. — Europe : Britain, France, Belgium, Nether- 

 lands, Germany, Switzerland, Italy, Austria-Hungary, Denmark, 



Norway, Sweden, Russia. 



Asia : Transcaucasia (338), Japan. 



North America: United States — ^Maine, Vermont (153). 

 Massachusetts, Connecticut, New York, Pennsylvania, Maryland, 

 New Jersey, Delaware, West Virginia, North and South Carolina, 

 Ohio, Michigan, Indiana, Alabama, Illinois, Mississippi, Wisconsin, 



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Missouri, Iowa, Minnesota, South Dakota, Kansas, Montana, 

 Wyoming, Colorado, California (159), Washington. Canada, New 

 Brunswick, Ontario, Manitoba. 



The most variable species of the Erysiphaceae. Starting w4th 

 the forms described as M. Hediuigii^ 21. Friesii and M. poiicilldta 

 by Leveille, examination of authentic specimens in the Kew Her- 

 barium shows conclusively that these represent but a single species. 

 The specific character on w^hich Leveille relied for the separation 

 of Hcdzvigii^ Friesii d.i\d pcjiiciUata was the presence of respectively 

 4, 6 and 8 spores in the ascus. Dealing only with the authentic 

 specimens from Leveille's Herbarium, we find up to 7 spores in 

 specimens named Hcdiuigii, 4—7 spores in Friesii, and 4— S spores 

 \n penieillata. It is quite clear, therefore, that the species under 

 consideration must be allowed a range of 4-8 spores. We may 

 note, too, that in these same specimens, the perithecia vary in 

 diameter from 68-1 10 [x. 



Winter (394) has already pointed out that these three species 



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of Leveille's must be united, and has adopted as the oldest name 

 for the plant Erysiphe alni DC, calling the present species, there- 

 fore, M. alni (DC.) Wint. Unfortunately, this identification is in- 

 correct, as De Candolle's E. alni is really the species now known 

 as Phyllactinia corylea. De Candolle described his species as fol- 

 lows (Syn. PI. Fl. Gall. p. 57): '* Hypophylla, filamentis plurimis 

 expansis longissimis liberis," and added as a synonym '' Sclerotiiini 

 Erysiphe alnea Schl, cent. exs. nr. 6?>.'' De Candolle added in 

 Lam. Enc. Meth. (Bot.) 8 : 219, these remarks, *' II y a beaucoup 

 de rapport entre cette espcce et la prccedente \_Erysiphe coryli 

 Hedw. = Phyllactinia corylea'\ ; elle en differe par Ics filaments de sa 

 base, beaucoup plus longs, plus etales et en plus grand nombre." 

 This description leaves no doubt that examples of Phyllactinia 



