24 A Monograph of the Erysiphaceae 



Distribution. 



The Erysiph 



world-wide distribution. 



It can, however, be said that their headquarters are in the North 

 Temperate Zone, as they occur in the greatest numbers in the Uni- 

 ted States and parts of Europe. The most southern record is 

 that of Pliyllactinia at the Beagle Channel, Tierra del Fuego, in 

 the extreme south of South America. One species probably, 

 Erysiphe cichoracearitm^ has been recorded from the tropical island 

 of St. Thomas, off the west coast of Africa ; Phyllactinia corylca 

 occurs in Guatemala, and Sphacrothcca pannosa is reported from 



m 



the West Indies. As regards the northern limit, Erysiphe cicliora- 

 cearum is found in Lapland, and Podosphaera oxyacantJiae in Green- 



land. 



As examples of species with a very wide range of distribution 

 may be mentioned Erysiphe poly gout ^E. cichoraceanim^ E. graininisy 

 MicrospJiaera alni, Podosphaera oxyaeanthae^ Uncinula salicis, SpJiae- 

 rotheca huvudi^ and Phyllactinia corylea. 



Arranging the species as they occur on the main areas of land 

 we have the following table : 



No. No. No. of No. of 



of spe::ies. of vars. endemic species. endemic vars. 



Europe, 27 5 9 3 



Africa, 7 



Asia, 



Australia and \ ^ 



New Zealand, f ^ 



3 4 



America, 31 7 14 5 



We find, therefore, that out of the 49 species and 1 1 varieties 

 of the Erysiphaceae^ no less than 2^ species and 9 varieties are 

 endemic in the above sense, that is to say, nearly four-sevenths of 

 the species and 9 out of the 1 1 varieties. 



These 27 ''endemic" species and 9 varieties are variously fur- 

 ther hmited in distribution, and it is interesting to note that most of 

 them are confined either to a single species of host -plant or to 

 one genus ; e, g., Erysiphe trina is known only from California on 

 the single species Querciis agrifoUa^ while E. toriilis has a wide 

 European range on Cornus sanguinca. 



The number of species confined to the Old World is iS, with 



