ANNUAL REPORT, 1933 17 



indol tolerance of certain fecal strains of Bad. coli. Information is now being 

 accumulated on the indol tolerance of certain strains of Bad. aerogenes and the 

 intermediate group. 



A Comparison of Devereux "Yeast Extract" Agar and Standard Agar for 

 Plating Milk Samples. (R. L. France.) A preliminary paper on this subject 

 was read before the Connecticut Valley Section of the American Society of 

 Bacteriologists. The results indicate that the "Yeast Extract" agar has no 

 advantages over the Standard agar when used for determining the bacterial 

 content of raw milk. Further data are being collected to determine the value 

 of the Devereux agar when used for plating pasteurized milk. Studies are being 

 made of several other media which might be used for determining the bacterial 

 content of pasteurized milk. In these studies an incubation temperature of 32° C. 

 is being used in addition to the standard temperature of 37° C. 



The Effect of Aging Temperature on the Bacterial Count of Pasteurized Ice 

 Cream Mixes. (W. S. Mueller and R. L. France.) The results of this investiga- 

 tion indicate that ice cream mixes may be held at 68° F. for six hours without 

 any significant increase in bacterial count. 



DEPARTMENT OF BOTANY 

 A. Vincient Osmun in Charge 



Black Root-Rot of Tobacco. (\V. L. Doran.) In 1932, tobacco was grown for 

 the ninth year in a field last limed in 1923. Its burn this year was unaffected 

 by the earlier liming. It was not of inferior quality, but had shorter leaves than 

 tobacco from unlimed plots. 



Tobacco plants in pot experiments were uninjured by ammonium sulfocyanate 

 800 pounds per acre, applied to soil 11 weeks before planting, but infection by 

 Thielavia basicola was not prevented. 



Aluminum phosphate 2 tons per acre, applied to soil in pot experiments, did 

 not pre\'ent black root-rot and did not affect growth of tobacco. 



Brown Root-Rot of Tobacco. (\V. L. Doran.) Growth of tobacco in brown 

 root-rot soil was improved by applications of calcium nitrate and orthophosphoric 

 acid together, but not by either alone. Sucrose 600 pounds per acre, applied to 

 soil free from brown root-rot, did not induce the disease. Copper sulfate 120 

 pounds per acre had no effect on brown root-rot. 



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

 was severe on greenhouse cucumbers in the fall of 1932, but the fungus (Perono- 

 plasmopara cubensis (B.&C.) Clint.) did not live on plants in greenhouses after 

 early January. It was next found here in the field on September 2, 1933, the 

 latest recorded date of its first appearance. Many fields escaped it until Septem- 

 ber 8, when picking was already over. 



Soil in which cucumbers were growing (in crocks) was watered only with solu- 

 tions of copper sulfate (0.29, 0.43, 0.57, 0.86, or 1.0 gram per gallon), applied 

 often enough to keep the soil at or near the optimum moisture content for growth, 

 beginning June 30 (when plants were 10 days old) and ending September 11. 

 Plants were inoculated with P. cubensis on September 3. None of these treat- 

 ments increased resistance to infection by this fungus, and all of them were 

 slightly injurious to the growth of plants. 



