260 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



believes that the restoration of pigment in the tissues is 

 not connected with oxidase action, and since there is much 

 evidence that it is not an oxidation change at all, it is 

 hard to see how its converse, the disappearance of colour, 

 can be due to reduction. 



The suggestion advanced by Willstatter (1913) to ex- 

 plain the behaviour of anthocyanin is that in presence of 

 strong alcohol intramolecular change takes place, with the 

 production of a colourless isomer. This can be paralleled 

 by the transformations of the triphenylmethane series of 

 dyes. 



PEROXIDASE REACTIONS OF RELATED SPECIES OF IRIS. 



Between the distribution of anthocyan pigments and 

 oxidases there is in many cases so close an agreement as 

 to amount almost to a definite proof that there is some 

 causal connection; but though there appears to be reason 

 to suppose that the production of colour necessitates the 

 presence of a complete peroxidase system during that 

 process, yet a number of facts ascertained by the writer 

 (1914, 1 and 3; 1915, 1) do not support such a conclusion. 

 These, however, are being investigated further with a view 

 to ascertaining the causes of such discrepancy. 



The examination of numerous species and varieties of 

 Iris was undertaken much on the lines of Keeble and 

 Armstrong's work, employing benzidine and a-naphthol as 

 microchemical reagents. In the course of the work, which 

 extended through two years, well over a hundred flowers 

 were tested, including members of about sixty or seventy 

 varieties. It was found that, adopting the classification 

 advocated by Dykes (1913) in " The Genus Iris," the most 

 striking feature of the results was that related varieties 

 had closely similar peroxidase distribution, irrespective, in 



