300 Oxydases and Pigments of Plants 



characterised by fairly regular and symmetrically placed white areas on 

 an otherwise uniformly blue ground. We have ground for believing, 

 both on account of the origin and of the genetical behaviour of these 

 plants, that the white areas represent what may be called inhibitory 

 patches. 



It is further to be mentioned that these white-zoned blue flowers 

 exist in two forms. In the one form, all the flowers of the plant are 

 marked symmetrically with the white areas and remain in this state as 

 long as they last. In the other form, certain of the flowers and par- 

 ticularly those which are produced late in the season show a blurred, 

 pale blue colour extending from the blue perimeter into the white 

 areas. The plants which exhibit the white areas sharply and per- 

 manently are homozygous, that is breed true to the character ; those 

 in which the areas tend to be blurred are heterozygous for the character ; 

 that is to say, they throw plants which bear uniformly blue flowers as 

 well as others with blotched blue flowers. 



The results of an investigation of the distribution of oxydase in the 

 corolla of the true breeding, white-zoned blue flowers are depicted in 

 Plate XIX, Figs. 11 and 12, and show in most striking and definite 

 manner that whereas both the epidermis and vascular bundles of the 

 blue areas give well marked oxydase reactions, no such reactions are 

 given by the white areas. Careful observation of the preparations 

 indicates (see Figs. 11 and 12, Plate XIX) that, although they exhibit 

 no sign of epidermal reaction, a faint bundle reaction may be traced 

 in some cases along the veins of the white areas. From the eye 

 of the corolla to the edge of each white patch, the bundle reaction is 

 very distinct ; but as soon as the bundle enters the white area the 

 reaction becomes either imperceptible or at most very faint ; and when 

 the veins pass from the white area into the blue region of the petals, 

 the bundle reaction resumes its distinctness. A comparison of Figs. 

 11 and 12, Plate XIX with the illustration (Fig. 2, Plate XIX) of the 

 oxydases of a uniformly coloured blue flower shows how remarkable is 

 the definition of the white areas of the blue, white-patched petals. The 

 curious attenuation of the bundle oxyda.se reaction over the white area 

 recalls that which occurs over the yellow eye of the flowers of 

 P. sinensis. 



Dominant whites and the white areas of the white-zoned blue 

 flowers are alike in that they yield no oxydase reactions, and they 

 stand in this respect in marked contrast with Recessive whites which 

 as we have shown give pronounced oxydase reactions. Recessive whites 



