1912.] 



The Distribution of Oxydases in Plants, etc. 



217 



subsequently with benzidine or a-naphthol and hydrogen peroxide the 

 characteristic peroxydase reactions are produced. The whole surface of the 

 petals becomes deeply coloured and the veins also stand out prominently. 

 Hence the flowers of dominant white primulas contain a substance which 

 inhibits but does not destroy the pigment-producing peroxydase. 



Where dominant white patches occur on otherwise self (uniformly) 

 coloured flowers, as is the case with certain strains of blue P. sinensis with 

 which we have worked, the benzidine reagent picks out the coloured areas in 

 brown and leaves the dominant white areas uncoloured. The a-naphthol 

 reagent picks out the veins with the utmost sharpness and leaves the 

 dominant white patches unstained except for an occasional fine line of colour 

 along the course of a vein which traverses the white patch. Beyond each 

 dominant white area as well as before reaching it, the bundle sheath 

 surrounding each vein is more deeply stained. Eecessive whites possess 

 both epidermal and bundle peroxydases. 



9. The observations on the epidermal and bundle peroxydases throw light 

 on the significance of the phenomenon presented by many cultivated flowers 

 which are known to florists as "ever sporting." Such flowers are 

 characterised by the sporadic appearance of splashes of colour on a white or 

 self-coloured ground. Ever sporting strains are familiar to everybody in 

 carnations and azaleas. In P. sinensis ever sporting strains are also 

 common. Thus the variety Mont Blanc Star bears white flowers with 

 magenta flakes. We are inclined to regard flaking as the effect of the 

 bundle peroxydase on the chromogen-containing cells neighbouring on the 

 bundle sheath. The white ground colour is to be attributed to an inhibitor 

 associated with and nullifying the epidermal peroxydase. 



The marked localisation of the pigmentation effected by the bundle 

 peroxydase, which localisation expresses itself in splashes, flakes, or lines of 

 colour, appears to be due to anatomical causes, such as the degree of develop- 

 ment of the cells of the bundle sheath and the nearness of the veins to one 

 another. 



10. The existence of two localised peroxydases which may induce pig- 

 mentation and may reinforce one another along certain tracts of tissue 

 provides material facts for the explanation of colour-range and colour pattern 

 in flowers. 



The investigations which are the subject of this communication have been 

 carried out jointly by the authors, who wish to share equally in the responsi- 

 bility for the results which they have obtained. 



The cost of the research, a detailed account of which will be published 



VOL. LXXXV. — B. Q 



