322 Agricultural Experiment Station, Ithaca, N, Y. 



• 

 portions of the leaf; this change takes place on the lower side of the 



leaf first, and the spots may thus be red above and green below. In 

 this green stage, which seems to have been heretofore overlooked, 

 the badly diseased leaves present a slightly thicker, corky appearance; 

 otherwise the disease is not readily apparent, especially where not 

 severe. This green stage lasts about a week or ten days; and about 

 June 15 the spots may be found changing to a dark brown color, 

 beginning on the lower side of the leaf. The tissue of the diseased 



.-I 



Fia. 8.— Part of an infested leaf , seen from below, showing several of the galls considerably 



enlarged. (From a photograph.) 



pai'ts or spots then present a dead, dry, brown or black, corky appear- 

 ance. Tlie spots are also more conspicuous on the lower side (Fig. 

 1), and remain unchanged until the leaves fall in the autumn. 

 They occur either singly, scattered over the surface of the leaves 

 or often coalesce, forming large blotches which sometimes involve 

 a large portion of the leaf (Fig. 1). The disease often appears on the 

 young leaves of the new growth during the summer. The spots are 

 then also first red and pass through the green stage to the brown. No 

 Variety of pears seems to be exempt from tlie attacks of tlic disease. 



