250 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



from copper boilers can, as first pointed out by Bourquelot 

 and Bougault, be readily distinguished from tap-water 

 and from that distilled from glass. The writer (1914, 3) 

 has suggested the use of this reaction as a test for copper 

 to be used in water analysis, in the absence of certain other 

 salts whose presence can readily be detected by the usual 

 tests. In the presence of hydrogen peroxide under standard 

 conditions, 1 part of copper can be found when present 

 in 100,000,000 parts of water. 



ADDENDA. Chodat and Schweizer (1915) have shown 

 that when tyrosinase, p-ciesol and glycerin are mixed and 

 kept for one hour in a solution saturated with hydrogen, a 

 red colour is produced five minutes after the admission of 

 oxygen. When oxygen was admitted directly, thirty 

 minutes elapsed before the production of the colour. This 

 furnished evidence of the union of the enzyme and its sub- 

 strate at a measurable rate. 



Bunzel (1915) has recently studied alfalfa laccase, and 

 has proved that the salts of strong bases with weak acids 

 accelerate oxidation by means of the hydroxyl ions liberated 

 from them. There is no quinol oxidizing enzyme in 

 Medicago saliva, as supposed by Euler and Bolin. 



Wolff and Rouchelmann (1915) have failed to find oxi- 

 dizable chroniogens in certain plants by extracting with 

 acid aqueous ether, though these are present as a rule. 

 It appears, however, that their list, which includes the 

 leaves of the oak, acacia and iris, really shows the presence 

 of inhibitors rather than the absence of chromogens. 



Reed (1915, 1) has succeeded in showing that enzymes 

 able to oxidize p-phenylenediamine are present in all the 

 algae he tested, 



