174 Report oF THE BOTANIST OF THE 
Il. POWDERY MILDEW ON FIELD-GROWN 
CUCUMBERS. 
In July, 1891, Humphrey’ announced the occurrence of a pow- 
dery mildew on cucumbers in America. In his annual report® for 
that year he gave an extended account of the disease and stated 
that it had been found on hot house cucumbers at Fitchburg, 
Mass., and Ithaca, N. Y. His next annual report’ contained 
drawings of the fungus and a brief recapitulation of the matter 
contained in the previous report. In Cornell Experiment Station 
Bulletin 31, page 31, Bailey has given a brief account of some 
experiments on the treatment of cucumber powdery mildew in the 
greenhouse. 
So far as known to the writer, the above mentioned articles 
constitute the whole of the literature of powdery mildew on 
cucumbers in America. In the Ninth Massachusetts Report® 
Humphrey states that in America it is not known to him to 
attack cucumbers grown in the open air. It is therefore worthy 
of mention that in September, 1899, we received from F. L. Esta- 
brook, of Athens, Pa., several leaves of field grown cucumbers 
which were thickly covered with a powdery mildew. Mr. Ksta- 
brook states that the mildew made its appearance some time in 
August and by September 22 was to be found upon every vine in 
the field and upon all parts of each vine excepting the younger 
leaves. In almost every case the older leaves near the root were 
the most severely attacked while the newer leaves toward the tip 
of the vine were generally free from it. The fungus was con- 
spicuous and occurred chiefly upon the upper surface of the leaves 
but occasional spots of it were to be found upon the under surface. 
The fruits were exceedingly bitter and many were misshapen, but 
5 Humphrey, J. E. The Powdery Mildew of the Cucumber. Mass. State 
Agr. Exp. Sta. Bul. 40: 3. 
6 Ninth Ann. Rept. Mass. State Agr. Exp. Sta., 1891: 222-226. 
7 Tenth Ann. Rept. Mass. Agr. Exp. Sta., 1892: 225-226. 
S1,-¢..°p. 222. 
