302 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



lumber, by which considerable portions of the wood of 

 certain trees, when exposed to the air by sawing into 

 planks or beams, were discoloured, and so depreciated in 

 value considerably. It has been demonstrated by Bailey 

 (1910) that this alteration is brought about by an oxidase. 



GENERAL AGRICULTURE. 



The preparation of ensilage has been investigated by 

 Russell within the last few years. He studied the changes 

 taking place in green maize stems packed closely together to 

 form a " silo." Bacterial action sets in, and also action of 

 the respiratory oxidases and other enzymes of the plant 

 cells. So large an amount of heat is generated by the 

 oxidases that the temperature rises to such a degree as to 

 inhibit further bacterial growth. The hydrolytic and pro- 

 teolytic enzymes still retain their activity, however, and a 

 complicated series of changes ensues, in which organic acids 

 appear among the products. 



NOTE. Rose (1915) has investigated the oxidizing power of healthy 

 apple bark, and of that injured by Illinois canker, and has found the 

 latter to be the more active. It also has a smaller amount of acid. He 

 considers that oxidation takes place in approximately the inverse ratio 

 of the acidity. The slowing down of oxidation in Bunzel's apparatus 

 is due to accumulation of acids. 



In the writer's opinion the effect of the acidity or alkalinity of the 

 medium is to alter the configuration of the molecule of the sugar, chro- 

 mogen or other substrate. Mathews and Walker ( 1909) have shown how 

 the oxidation of cystein is affected by the acidity of the medium, and in 

 conjunction with others Mathews has studied the subject extensively. 

 E. A. Werner, too, has proved that the configuration of the thiocarbamide 

 molecule is altered by the acidity or alkalinity of the medium ; a number 

 of his papers on this subject have appeared in the Journal of the Chemical 

 Society during the last three years. 



In one configuration a molecule is often more reactive than in another. 



