250 Physiologie. 



of enzymes; and sMartin Fischer that it increases the water- 

 absorbing power of coUoids. 



Other dormant seeds of the Rosaceae are now being studied 

 with the hope of gaining further knowledge on this point. 



Jongmans. 



Harvey, E. M., The Castor bean plant and Laboratory 

 air. Contributions from the Hüll ßotanical Laboratory. 

 17 8. (Bot. Gazette. LVI. p. 439-4^2. 1913.) 



It is well known that the leaves of the castor bean {Ricinus 

 communis) are likely to show nastic drooping after the plant has 

 been brought into the laboratory. On account of the apparent defi- 

 niteness of this response, it seetned probable that the plant would 

 prove useful as a delicate test for certain gaseous impurities in 

 laboratory air. 



Potted seedlings grown under ordinary greenhouse conditions 

 until they had developed 5 tili 7 leaves, including the cotyledons, 

 were exposed to known concentrations of ethylene and illuminaiing 

 gas. The results proved that the plant has great capacity for response 

 to low concentrations of ethylene. The lowest concentration tried 

 was one part ethylene to 10.000.000 of air. With this amount the 

 response was absolutely definite. Parallel experiments with illumi- 

 nating gas and ethylene, where the ethylene constituent of the 

 former was about equal to the ethylene in the corresponding eth}'^- 

 lene-air mixture, g^ive results similar in kind and degree. This fact 

 indicates that the ethylene of the illuminating gas is responsible for 

 the reaction. 



In conclusion it may be stated that the castor bean plant has 

 proved capable of giving an easily observed response to extremely 

 small amounts of ethylene; and on account of this fact the plant 

 seems particularly useful for the detection of harmful gaseous impu- 

 rities in the air of laboratories and greenhouses. Jongmans. 



Hawkins, L. A., The effect of certain Chlorides singly 

 and combined in pairs on the activity of Malt diastase. 

 (Bot. Gazette. LV. p. 265—285. 1913.) 



The present investigation deals with the effects of sodium, 

 potassium, calcium, magnesium, cupric and ferric Solutions, alone 

 and in certain binary combinations, on the hydrolytic activity of 

 Merck's "diastase of malt absolute", the enzymatic mixture acting 

 on a boiled Solution of washed maize starch, at 50° C. The disap- 

 pearance of the ability of the starch to give a color reaction with 

 iodine was taken as the end point of the reaction, and the reci- 

 procal of the time period which elapsed before this end point was 

 attained (considering the time period of the control without added 

 Salt as unit}^) was used as a measure of the intensity of enzyme action. 

 A Wide Variation is clearly shown in the influence of the diffe- 

 rent Chlorides upon diastatic action, which is probably to be 

 related to the properties of the various cations emplo3^ed. More or 

 less pronounced acceleration of starch hydrolysis is shown for all 

 of the salts used at different concentrations; the highest acceleration 

 found is for iron (291 per cent) and the next highest for calcium 

 (269 per cent). Retardation of hydrolysis is shown at high concen- 

 trations for all salts excepting sodium Chloride and potassium chlo- 



