200 A Monograph of the Erysiphaceae 



piilva 



Icniwn (319), V. thapsifonne (263), V. Thapsus (230), Verbena 

 angustifolia, V. Aublctia, V. bractcata (61), V. hastata, V. laevis, 

 V. officinalis {(iO), V. stricta, V, nrticifolia, Vcrbesina encclioides 

 (363), V- occidcntalis (9), Vernonia Baldiuini, V. fascicidata, V. 

 Novcboracensis, Xanthiiim Canadense, X. Stnunariimi. 



Distribution. — Europe : Britain, France, Belgium, Netherlands, 

 Switzerland, Italy, Germany, Austria-Hungary, Servia (318), 



Greece, Denmark, Norway, Sweden, Lapland (192), Finland (192), 

 Russia. 



Eg> 



New Zealand. 



J 



North America: United States— Maine, New Hampshire, 

 Vermont, Massachusetts, New York, Pennsylvania, Maryland, 

 New Jersey, Virginia, North and South Carolina, Ohio. Michicran, 

 Indiana, Alabama, Illinois, Mississippi, Wisconsin, Missouri, Iowa, 



Minnesota, 



Montana, Idaho, Wyo 



Colorado, Utah, California, Washington. Canada— Newfound-- 



land, New Brunswick, Ontario. 



very 



difficult species to recognize under the microscope. In rare cases, 

 it closely approaches certain forms of E. polygoni, with which it 

 has been much confused ; E. cichoraccarnm and E. polygoni, how- 

 ever, must certainly be considered as distinct species. In by far 

 the greatest number of cases, the present species may be at once 

 distinguished by the numerous, regularly 2-spored ascl. The com- 

 paratively few forms of E. polygoni which have numerous asci are 

 always 4-8-spored. Although E. cichoracearum shows rarely one 

 or two asci in a perithecium with 3 spores, and although in E. 

 polygoni, as a rare exception, an ascus may contain only 2 spores, 

 yet as the result of an examination of many hundred specimens of 

 both species, it appears to me safe to consider the 2-spored ascus 

 as the central specific character of E. cichoracearum, and the ^-d,- 

 spored ascus as that of ^. polygoni. Usually unfailing characters 

 are also found in the large wider asci and larger, distinctly wider 

 spores of the present species. Often, moreover, E. cichoracearum 

 has a habit, difficult to define, by which it is known from E poly- 



