ANNUAL REPORT, 1931 201 



of cellulose. A nitrogen-poor soil with one per cent added cellulose (wheat straw) 

 was treated in the same way as the compost soil. At all temperatures there was 

 loss of nitrates in the presence of cellulose. Sodium nitrate, calcium carbonate, 

 and calcium sulfate added to the soil separately and in combination at tempera- 

 tures of 15° C, 25° C, and 35° C, did not prevent nitrate depletion in soil to 

 which cellulose had been added. The loss of nitrate appeared to be greater when 

 the calcium carbonate alone was added to the soil. 



Laboratory Service. (Ralph L. France.) A total of 1,24S examinations 

 was made in this laboratory during the past year. Briefly summarized they may 

 be classified as follows: 



Bacterial counts of milk 1,033 



Sanitary analysis of water 149 



Miscellaneous 66 



Under miscellaneous are included examination of milk for garget or other 

 abnormal udder conditions, examination of various food products for organisms 

 causing spoilage, and chemical analysis of milk. 



The total number of bacterial examinations of milk has increased materially 

 over previous years. This is a clear indication not only that the laboratory is 

 providing valuable service to the milk control program of the Valley, but also 

 that dealers and producers now realize that a clean, wholesome product influences 

 purchase by the consumer. 



The total number of legume cultures distributed during the year has decreased 

 considerably. In all probability this is due to the statewide distribution of 

 cultures prepared by commercial concerns under the supervision and control of 

 the United States Department of .\griculture. 



The Indol Tolerance of the Colon-Aerogenes Group of Bacteria as a 

 Possible Means of Differentiating Fecal and Non-Fecal Strains Occur- 

 ring in Drinking-Water Supplies. (Ralph L. France.) The preliminary 

 work on this project has been completed and the data are being assembled for 

 publication. The results indicate that the methods for sanitary w-ater analysis 

 now employed in the majority of laboratories may lead to inaccurate interpreta- 

 tion of experimental results. Experimental evidence seems to indicate the 

 necessity of submitting Colon bacilli found in water to various biochemical tests 

 for the differentiation of fecal and non-fecal types of this organism rather than 

 placing an interpretation of sanitary quality upon the routine Endo plate and 

 lactose broth fermentation. A discrepancy of 40 per cent was found to exist 

 between these two confirmation methods. The writer now proposes to submit 

 these fecal and non-fecal strains of the Colon bacillus to various dilutions of 

 indol in an effort to determine a possible difference in the indol tolerance of the 

 organisms. 



DEPARTMENT OF BOTANY 

 A. Vincent Osmun in Charge 



Tobacco Black Root-Rot. (W. L. Doran). Loss in yield of tobacco in 

 plots last limed in 1923 is decreasing. The decrease in yield caused by black 

 root-rot in these plots is now only about 16 per cent, or one-third of what it was 

 in 1925. But the soil in these limed plots has not yet become any more acid. 



