262 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



many cases, of pigmentation. Owing to the considerable 

 alterations produced in the peroxidase by keeping in the 

 dark, it is essential for a truly comparable examination 

 that all the flowers should have been exposed to equal 

 illumination. Since some of the plants flowered in Feb- 

 ruary, and others in succeeding months up to July, it was 

 not possible to secure uniformity in this condition. Never- 

 theless, as the results obtained with members of one variety 

 picked in the gardens and examined in the laboratory 

 under the weather conditions existing one day agreed well 

 with those given by the same variety on succeeding days, 

 one is led to the conclusion that this is not a serious source 

 of error. Direct experiment has also confirmed this, as 

 will be shown farther on. 



In a general way it may be said that the power of 

 oxidizing benzidine is more widespread and of greater 

 intensity than that of oxidizing a-naphthol, yet in many 

 cases the latter reagent is strongly acted on in the epidermis. 

 The failure of the flowers to react with a-naphthol is due 

 to an inhibitor, which is apparently able to stop the action 

 on it to a greater extent than that on 1 benzidine. Its 

 removal by the cyanide method is illustrated by the fol- 

 lowing table. Hydrogen peroxide was added in every case, 

 as no reaction takes place without it. 



With regard to the restoration of the original anthocyan 

 pigment, when the decolorized falls are placed in water, 

 the chief factor seems to be the intensity of colour in the 

 untreated tissues. For when this is not fairly deep, the 

 losses sustained through diffusion, and destruction by re- 

 ducing agents too, in all likelihood, are sufficient to prevent 

 any reappearance of anthocyanin. 



In the table (No. LIX.) it is not easy to correlate per- 

 oxidase distribution with that of anthocyanin. It appears, 

 however, that in Nos. 1 to 4 the supply of chromogen is the 



