DISEASES OF PLANTS. 249 



Downy mildew (Plasmopara cubensis) attacks the older leaves near 

 the center of the vine and gradually spreads outward. Irregular yellow 

 spots appear which in warm weather enlarge rapidly, the whole leaf 

 soon turning yellow and drying up as if frosted. In cool weather the 

 spots spread less rapidly, their centers becoming dry and of a light- 

 brown color. Hot and moderately damp weather favors the growth of 

 the fungus. It is usually most destructive in August. Only a few mis- 

 shapen cucumbers are produced after it becomes fully established. 



The structure of the cucumber leaf and of the mildew are popularly 

 described and illustrated and the nature and life history of the fungus 

 noted. The history of the disease is briefly given. The botanical rela- 

 tionship and the host plants of the fungus are also popularly discussed. 



An experiment was conducted on If acres of cucumbers at Wood- 

 bury, New York, to test the value of Bordeaux mixture as a remedy for 

 the mildew. Thirty rows of cucumbers were sprayed 7 times from July 

 13 to September 9, two sprayings being made with Bordeaux mixture 

 of the 1:7 formula; 2 of the 1:11 formula; and 3 of the 1:8 formula. 

 Ten rows were left unsprayed. Two rows in the midst of the unsprayed 

 ones were sprayed 1 times from August -'1 to September 9, one row with 

 Bordeaux mixture of the 1 : 7 formula, and the other of the 1 : 11 formula. 

 The spraying was done with a knapsack sprayer. A detailed chrono- 

 logical record of the experiment is given together with a diagram show- 

 ing the arrangement of the different plats. Downy mildew was first 

 observed August 7. about the time of the first picking. Less than a 

 week later every hill of the unsprayed rows showed the disease, while 

 only a few plants of the sprayed rows were affected. In two weeks 

 from the time the disease appeared the unsprayed rows were yellow 

 throughout and picking was practically finished, while the sprayed 

 rows were green and produced a large number of cucumbers. From 

 this time the disease gradually spread on the sprayed vines, though they 

 continued to yield well until frost, a month after the unsprayed vines 

 stopped yielding, producing in the month $2<i<> worth of cucumbers. 

 The cost of spraying, including the cost of material and labor, was but 

 $14.31, or at the rate of -$9.50 per acre. The author believes that if all 

 the plants had been sprayed the results would have been even more 

 marked, since the sprayed plants undoubtedly received infection con- 

 tinually from the unsprayed ones. Further experiments will be neces- 

 sary to determine the strength of Bordeaux mixture to be used. 



The bulletin also contains discussion of spraying muskmelons and 

 watermelons and the chances of being poisoned by eating sprayed 

 melons. Detailed directions are given for the preparation of Bordeaux 

 mixture. A discussion is made of spraying machinery, a j>artof which 

 is a reprint from Bulletin 75 of the station (E. S. B., 6, p. 833). 



On the development of the -white rot fungus of grapes, P. Vial A 

 {Compt. Rend. Acad. Sci. Paris, 121 {1897), No. 2, pp. 105, 1 06). —Notes 

 are given on the life cycle of Gharrinia diplodiella, which causes the 

 so-called white rot of grapes. The fungus has been known in Europe 



