I2 o SCIENCE PROGRESS 



class were indeed the only ones to give well-marked indirect 

 reactions with guaiacum resin. Nevertheless most algae tested 

 give a colour with the benzidine reagent, more especially in their 

 cell walls. But this must not be regarded as always indicating 

 an oxidase, for in some of the cases most thoroughly examined — 

 certain of the green algae — the blue colour was found to be pro- 

 duced at an equally rapid rate immediately after boiling. These 

 investigations on algae are at present being continued. 



The widespread distribution of oxidases and chromogens in 

 land plants shows that Palladin's views on respiration are of 

 very wide application. The conditions of life of water-dwelling 

 plants are so different from those of sub-aerial vegetation that 

 it would not be surprising if the respiration of the former was 

 carried on in a somewhat modified manner. Reducing sub- 

 stances occur in their tissues, and I have not yet found it 

 possible to detect masked oxidases in them by removal of 

 inhibitors by any of the methods previously described. It is 

 noteworthy that catalase was found in every case, being remark- 

 ably active in many. 



The Oxidases in relation to Pigmentation. — It has been known 

 for a considerable time that there is a causal connection 

 between the occurrence of oxidases and sap-pigments in stems 

 and the veins of leaves. Reinke x investigated the chromogens 

 as far back as 1882. More recently they have been studied by 

 Wheldale, 3 Molisch, 3 Keeble, Armstrong and Jones, 4 Bartlett, 5 

 and others. The nature of the sap-soluble anthocyan pigments 

 cannot yet be regarded as firmly established. Wheldale regards 

 the anthocyanins as oxidation and condensation products of 

 colourless chromogens which are present in living cells as part 

 of a glucoside molecule. The hydrolysis of the glucoside is 

 considered to be a reversible enzyme action, and only the free 

 chromogen, which belongs to the aromatic group of chemical 

 compounds, can be attacked by the oxidase. This view, which 

 greatly stimulated research, has recently been shown to be in 

 need of some modification, or at any rate not to hold univer- 



1 Reinke, Zeitschr. f.physiol. Chem. 1882, 6, 263. 



' Wheldale, Progressus Rei Botaniccz, 1910, 3, 457 ; also Journ. of Genetics, 

 1911,1, 133. 



3 Molisch, Bot. Zeitschr. 1905, 63, 145. 



4 Keeble, Armstrong, and Jones, Proc. Roy. Soc. 1913, B, 87, 113. 



4 Bartlett, H. H., Bull. No. 264, Bureau of Plant Industry, U.S. Dept. of Agric. 



