Uncinula 93 



of its occurrence there, by Harkness and Moore (159) rests on an 



error. 



Eriksson states (119) that the present species causes much 

 damage to young trees'of Ari^r in the nurseries at Stockholm, and 

 recommends as preventive measures the collection and burning of 



the diseased leaves. 



The conidial stage of the present species was described as 



OidiujJi accris Rabenh. Flora, 12 : 207- 1854. 



var. Tulasnei (Fckl.) [Figs. 90-9-] 



Mucor Erysiphe Schrank, Prim. Fl. Salisb. 240 (partim). 1792. 

 Erysiphe biconds Fr. Syst. ^lyc. 3 : 244 (partim). 1829. 

 Erysibc accris Wahl. Fl. Suec. 2 : 1086. 1833. 

 Uncinula biconds Lev. Ann. Sci. Nat. III. 15 : 135 (partim). 



1851. 



U. Tulasnei Fckl. Fung. Rhen. ur. 1746. 1866 ; Fckl. Symb. 

 Myc. 81. 1869-70; Sacc. Syll. Fung, i: 9. 1882 ; Wint. in 

 Rabenh. Krypt. Fl. Deutschl. i' : 41. 1884. 



Exsicc. : Fckl, Fung. Rhen. 1746; Syd. Myc. March., 2S35, 

 ^4232, and 2764 sub U. biconds ; Rab. Fung. Eur. 1915 ; * de 

 Thuem. Myc. univ. 644, and Fung, austr. 1251 ; * Erikss. Fung. 



par. scand. 35. 



Mycelium usually epiphyllous, very rarely amphigenous, per- 

 sistent, densely compacted, forming either roundish circumscribed 

 spots, or irregular blotches following the veins of the leaf, often 

 becoming confluent and covering the upper surface of the leaf ; 

 perithecia subgregarious or scattered, globose-depressed to len- 

 ticular, 156-268 /i in diameter, averaging 205 /i ; appendages 

 numerous, %-}{ diameter of the perithecium, simple or bifid, 



(usually mostly simple intermixed with a few bifid ones), color- 

 less, smooth, thick-walled, with the lumen nearly or wholly oblit- 

 erated in the lower part; asci 8-20, broadly ovate or elliptic- 

 oblong, 64-98 X 40-50 /i, averaging 80 x 43 Z' J spores 8, rarely 



6 or 7, 26-30 X 14-17/^. 



Hosts.— Acer monspcssulanum, A. platanoides, A. pscudo-Pla- 



tanus (176) (210). 



Distribution.— '^\5v,QV^: France, Germany, Switzerland (176). 



Austria-Hungar>% Norway, Sweden, Russia. 



U. accris, var. Tulasnei is somewhat variable in the nature of 

 its appendages ; sometimes these are all simple, when there is a 



