168 Physiologie. 



pressure. The failure of a leaf to respond to shaking is probably 

 connected with the small inertia of the sensative hairs, and the 

 slight resistance offered bj'" the air to their passage through it. 

 Water at room temperature causes closure only when it bends a 

 sensative hair. After one mechanical Stimulus there is a short period 

 during which a second mechanical Stimulus is ineffective. Moore. 



Clowes, G. H. A., A critical studj^ of the conditions under 

 Avhich zymase and its associate co-enzyme bring about 

 alcoholic fermentation. (Proc Soc. Exp. Biol. Medic. New York. 

 VI. p. 44—46. Jan. 15. 1909.) 



A Stahle preparation containing relatively large quantities of 

 zymase was obtained from Buchner's Dauerhefe, and similar 

 quantities of a relatively stable boiled extract of yeast containing 

 the co-enzyme were also obtained. Experiments were then conducted 

 the object of which was to determine the effect of varying propor- 

 tions of co-enzyme used in conjunction with a constant amount of 

 zymase and vice versa. It was found that the velocities of reaction 

 and the fermentation and results were directly proportional to the 

 number of units of co-enz^^me employed up to an optimum concen- 

 tration, after which a fall in the value of both these quantities was 

 to be observed. The same phenomenon exhibited itself when varying 

 proportions of the Z3'^mase were employed with a constant amount 

 of co-enzyme. Formulae for calculating the velocity of reaction and 

 showing its relation to the concentration of the zymase and the 

 co-enzyme are given. Moore. 



Hartwell, B. L. and F. R. Pember. Sodium as a partial Sub- 

 stitute for potassium. ('Rep. Rhode Island Agr. Exp. Sta. p. 

 243—285. 1908.) 



Experiments mainly with wheat seedlings in water cultures 

 under varying conditions, to determine whether the beneficial 

 effects produced by the application of sodium to soils containing 

 but little available potassium, was due to a direct action of sodium 

 as a plant nutrient. The results seemed to show that the beneficial 

 effect of sodium was not due to the increase of osmotic pressure, 

 to a change of the acidity or alkalinity of the nutrient Solution, 

 nor to overcoming the effect of unfavorable quantitative relations 

 of the nutrients in Solution; although sodium salts maj^ under cer- 

 tain circumstances act advantageoush^ in these ways. Apparenth' in 

 some plants, certain of the uses of potassium may be performed 

 by sodium, although the principle functions of potassium cannot be 

 performed by any other dement. Moore. 



Hartwell, B. L. and F. R. Pember. The relative toxicit)?- of 

 ferrous sulphate to barley and rye seedlings. (Rep. Rhode 

 Island Agr. Exp. Sta. p. 286—294. 1908.) 



No marked difference in the effect of ferrous sulphate on rj'e 

 and barley was shown, — a distinct contrast to the effect of lime 

 on seedlings of these plants. Moore 



Hawkins, L. A., The porous clay cup for the automatic 

 watering of plants. (Plant World. XIII. p. 220-227. Sept. 1910.) 



An account of experiments to demonstrate the effect of the use 



