iqiq] current literature 277 



The general results show decrease in the amount of digestion of starch by the 

 fungus in the presence of low concentrations (M/io,ooo and M/ioo,ooo) of the 

 chlorides and sulphates. The view is taken that the decreased digestion is 

 caused by decreased secretion of diastase rather than by inhibition of the 

 activity of secreted diastase. Potassium salts decrease secretion more than 

 corresponding sodium salts. Experiments with nutrient solutions instead of 

 single salts showed the same general effect, decreased secretion. No evidence 

 was found to support the idea that calcium or potassium is intimately related 

 to diastase formation. On the other hand, nitrogen may possibly have some 

 relation to enzyme formation. Nitrates added singly increase the actual 

 amount of starch digestion, but since the mycelial growth is much increased, 

 there is really less digestion per unit of dry weight of mycelium. — C. A. Shull. 



Reaction of the medium and nitrogen assimilating organisms. — Fred and 

 Davenport'7 have studied the relation of the legume bacteria and Azobacter to 

 low concentrations of acids and alkalies. When sulphuric acid was added to the 

 nutrient solutions, the following hydrogen ion concentrations were found to be 

 critical for the various legume organisms: alfalfa and sweet clover, Ph 4.9; 

 garden pea, field pea, and vetch, Ph 4 . 7 ; red clover and common beans, Ph 4 . 2 ; 

 soybeans and velvet beans, Ph 3 3; lupines, Ph 3 . 15. The authors believe a 

 correlation exists between the acid resistance of the bacteria and the acid 

 resistance of the higher plant with which they are associated. These organisms 

 are not injured by normal alkali additions to the culture medium until the addi- 

 tion is about 10 times that of sulphuric acid producing injury. There seems to 

 be little difference in the several strains as to the alkali resistance. 



Azobacter is limited to a much narrower range of reaction than are the 

 legume organisms, the critical limits being 6 . 5 Ph for acid and 8 . 6 Ph for alkali. 

 It is to be regretted that the reaction was not determined by the gas chain as 

 well as by the colorimetric method. — Wm. Crocker. 



9 



Transpiration. — Duggar and Bonns'* have issued a third paper from the 

 Missouri Botanical Garden on the effect of a film of Bordeaux mixture and 

 other films on the transpiration of leaves. In potted mesophytes such a 

 film increases generally the transpiration at night, but has less or no effect 

 during the day. Similar behavior is shown by excised leaves. In Cyperus 

 esculentus, a plant of xerophytic surface modification, such films have no 

 effect on transpiration rate. The writers offer as tentative the following 

 explanation: the film of Bordeaux mixture on the surface of a plant in a state 

 of guttation acts more or less as a bibulous surface, taking water directly 

 from the interior of the plant, through at least some continuous water channels 



'7 Fred, E. B., and Davenport, Audrey, Influence of reaction on nitrogen- 

 assimilating bacteria. Jour. Agric. Research 14:317-336. 1918. 



•8 Duggar, B. M., and Bonns, W. W., The effect of Bordeaux mixture on the 

 rate of transpiration. Ann. Mo. Bot. Gard. 5:153-176. 1918. 



