300 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



in the respiration of the cell. Palladin's theory of the 

 mechanism of respiration has already been briefly alluded 

 to in a previous section. Though a discussion of the 

 recent work on this subject would be of great interest, it 

 is omitted here, both on account of the large proportions 

 which it has assumed, involving as it does many questions 

 of a chemical nature, and because the writer's acquaintance 

 with it is not based on laboratory experience. 



SECTION II. THE BEARING OF OXIDA8E INVESTIGATIONS 

 ON TECHNOLOGY. 



LACQUER INDUSTRY. 



In addition to the interest of oxidase study for the silk 

 and sugar industries mentioned in the last section, there 

 are several other more direct applications. The researches 

 of Yoshida in 1883 showed that an oxidase was concerned 

 in the production of the well-known black varnish obtained 

 from the milk-like sap of the lac-tree, Rhus vernicifera, and 

 allied species. He obtained from the sap an acid urushic 

 acid which, when oxidized by the enzyme, becomes black 

 and forms the basis of the varnish which is so much used 

 in China and Japan. Eleven years later Bertrand con- 

 firmed and extended Yoshida's work, giving the name 

 " laccase " to the enzyme, and pointing out the relation- 

 ship of urushic acid to the hydroxy-detivatives of the 

 benzene series. 



TEA AND COCOA TRADE. 



In the preparation of tea, also, an oxidase has been proved 

 by Mann to play an important part. In green tea the leaf 

 is roasted immediately after picking, before any appreciable 

 oxidation takes place. In black tea, on the other hand, 

 an oxidation of the tannin is effected by an oxidase of the 

 laccase class, resulting in the production of a soluble brown 



