ANNUAL REPORT, 1934 23 



tubes was no more satisfactory than the use of the brilliant green bile broth in 

 place of lactose broth as a presumptive medium. 



A Comparison of Several Media for Determining the Bacterial Content of 

 Milk by the Plate Count Method. (Ralph L. France and Bernard E. Supowitz.) 

 The results of this investigation indicated: (1) that the Devereux "yeast extract" 

 agar was not a satisfactory medium for plating raw and pasteurized milk; (2) 

 that an exhaustive study of the nutritive requirements of the common milk 

 organisms is needed; and (3) that an incubation temperature of 32°C. is more 

 satisfactory than the present standard temperature of 37°. 



Laboratory Service. (Ralph L. France.) Following is a list of the number 

 and types of examinations made in the laboratory during the past year: 



Milk (bacteria counts) 997 



Water 80 



Miscellaneous: 



*Butter Fat (Milk) 48 



*Total Solids (Milk) 1 



Sediment (Milk) 7 



Added Water (Milk) ■. . 1 



Throat Swabs 10 



Smears 2 



Total 1,146 



*Analyses made by the Feed Control Laboratory. 



DEPARTMENT OF BOTANY 

 A. Vincent Osmun in Charge 



Downy Mildews of Cucumber and Lettuce. (W. L. Doran.) Greenhouse 

 cucumbers were sprayed with resin 1:13s 1 or Bordeaux mixture 3:3:50, four times 

 at intervals of one week, and inoculated with Peronoplasmopara cubensis after 

 the first and third applications. Resin was of some benefit, but was inferior to the 

 Bordeaux mixture in preventing infection. Resin injured the foliage slightly, 

 but more than did Bordeaux mixture. 



Cucumbers were grown in soil to which the following salts of copper in these 

 amounts per square foot had been applied: cupric aceto-arsenite (1 to 4 grams), 

 cupric carbonate (2 to 4 grams), cuprous cyanide (2 to 4 grams), copper-lime 

 dust 80-20 (10 to 30 grams), copper sulfate (3 to 5 grams), or copper sulfocarbolate 

 (3 to 6 grams). No protection against infection of the cotyledons of the seedlings 

 by P. cubensis resulted. 



The dates of the first appearance of downy mildew of cucumber in the fields 

 here (as on September 4 in 1934) have been noted and recorded for the past ten 

 years. Years in which the disease has appeared early (August 4 to 15) have aver- 

 aged 72 percent more inches of rain and 57 percent more rainy days in July than 

 have years in which the disease appeared late (August 18 to September 4). The 

 weather of August seems to have less effect than does the weather of July. 



Infection of lettuce by Bremia lactucae was prevented, well and equally well, 

 by Bordeaux mixture 4:4:50, 2:2:50, and 1:1:50, applied 6 times at intervals 



'For method of preparation, see Mass. Agr. Expt. Sta. Bui. 293, p. 16, 1933. 



