ANNUAL REPORT, 1937 29 



the Dacteria to reduce methylene blue and the stability of the vitamin in their 

 presence. The cultivation of the culture in atmospheres of carbon dioxide and of 

 hydrogen respectively revealed that carbon dioxide apparently exerted a protec- 

 tive action on the vitamin, while hydrogen had no such action. The analogy is 

 that the carbon dioxide produced by bacteria from readily fermentable carbo- 

 hydrates can protect vitamins from destruction in the human intestine. The 

 bacteria employed were several strains of the Coli-Aerogenes group and of the 

 Salmonella group, and one each of Eberthella typhi, Bacillus subtilis, and Proteus 

 vulgaris. 



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

 and types of examinations made during the past year: 



Milk (bacteria counts) 1,398 



Ice Cream (bacteria counts) 89 



Water 119 



Miscellaneous: 



Sediment (Milk) 16 



Mastitis 1 



Wash Water 12 



Throat Swabs 15 



Smears 3 



Total 1,653 



Bacteriological Study of Machinist Cutting Compound (James E. Fuller.) 

 This survey study was reported in Journal of Bacteriology 34 (No. 2):241, 1937. 



DEPARTMENT OF BOTANY 

 A. Vincent Osmun in Charge 



Effect of Soil Temperature on Gardenia. (L. H. Jones.) In a series of experi- 

 ments carried on in the soil temperature tanks, it was determined that a chlorosis 

 of gardenia may be induced at any time of the year by a soil temperature of 

 18° C. and less and develops more intensely directly as the soil temperature is 

 lowered. The number of days necessary to induce chlorosis varied with the health 

 of the plants at the time the temperature was lowered. Hard plants growing at 

 medium temperatures developed chlorosis more slowly than soft plants grown at 

 high temperatures. A sharp rise in soil temperature maintained for 13 days was 

 sufficient to initiate the return of a healthy green color. 



Soil temperature affected growth rates and the final size of the leaf. The rate 

 of growth was inversely correlated with the intensity of the development of 

 chlorosis. The size of the leaf was correlated with soil temperature directly as the 

 soil temperature was increased. 



Plants which had been growing at a high soil temperature and were suddenly 

 subjected to a low soil temperature were unable to absorb enough water to main- 

 tain turgidity in the leaves. The plants wilted in sunshine but recovered turgidity 

 at night. Recovery was complete in about two weeks. 



Lowering the soil temperature to 10° C. or less caused a rapid senescence of the 

 oldest leaves. 



There were indications that a low soil temperature altered the vegetative or 

 growing phase to a reproductive or flowering phase. 



