31 



Quercus imbricaria and Ouercus velutina might be 

 regarded as the parents of the Preston oak. 



I have becided that the Columbus oak is a hybrid 

 between Quercus imbricaria and Q. rubra. The great 

 similarity which the whole tree, the leaves, and the fruit 

 bear to the Red oak, also the fact that the Red oak 

 is very common in its vicinity, while the other 

 members of the Red oak group are very rare; make me 

 believe that the Red oak is the other parent of this 

 hybrid. 



LIST OF THE "WHITE MILDEWS" (ERYvSIPH- 



EM, LEV.) OF CUYAHOGA COUNTY AND 



OF THEIR HOST-PLANTS, 



BY EDO CLAASSEN. 



1. Erysiphe cichoracearum D. C. on Ambrosia arte- 



misiaefolia, L., Sept. 15, Oct. 6; on Ambrosia 

 trifida, L., Sept. 15; on Aster laevis, L. Aug. 

 31, Oct. 17; on Aster paniculatns. Lam., Oct. 

 6; Solidago canadensis, L., Oct., 22; on Ver- 

 bena hastata, L., Sept. 29; on Verbena urticae- 

 folia, L., Sept. 29; on Verbesina alternifolia, L., 

 Oct. 15; on Vernonia gigantea, Walt. 



2. Erysiphe communis (Walt.) Fr., on Aquilegia can- 



adensis, L., Aug. 18. 



3. Microsphaera alni (D. C.) Winter, on Castanea 



dentata (Marsh.) Sudw., Aug. 14, Oct. 10; 

 on Cornus candidissima. Marsh., Aug. 20, 

 Sept. 29; on Lonicera ciliata, Muhl., Sept. 29; 

 on Platanus occidentalis, L., Oct. 3; on Sambu- 

 cus canadensis, L., Aug. 17, Oct. 10; on Syr- 

 inga vulgaris, L., Sept. 29, Oct. 20; on Vibur- 

 num acerifolium, L., Sept. 29. 



