290 Oxydases and Pigments of Plants 



is due, not to authocyan, but to plastid pigments ; and it is a note- 

 worthy and general fact that the region of the yellow eye shows no 

 oxydase reaction except in the epidermal hairs which give with benzidine 

 a deep brown-black colouration. The failure of the oxydases of this 

 region of the eye to react with a-naphthol or benzidine is to be attributed 

 to the inhibition of oxydase by the chloroplasts. 



We have investigated the oxydase contents of the corollas of many 

 other colour varieties of P. sinensis, e.g. Crimson King, Coral Pink and 

 Giant Red among the reds ; various magentas and lavenders, e.g. Giant 

 Lavender; and Czar, Cambridge Blue, etc. among the blues, and though 

 the extent of the reactinn of epidermal and of bundle oxydases varies 

 considerably in the several varieties it is characteristic of them all. 



Of white-flowered varieties of P. sinensis, genetical research has 

 shown that there are two kinds, which are known respectively as 

 Recessive Whites and Dormant Whites. 



(2) Recessive White Varieties. 



The Recessive Whites show by their behaviour when crossed with 

 coloured varieties that they lack a factor for colour. When crossed 

 with a coloured variety they yield a coloured F^ which on self-fertilization 

 gives rise to an F^ generation composed of 3 coloured : 1 white. 



The usual and evidently proper interpretation of this result is that 

 recessive whites lack a factor for colour which is possessed by the pig- 

 mented varieties. The cross is therefore to be represented thus: 



c X C 



F, = Cc 



i^,= 3C:lc 



= 3 coloured : 1 white. 



As we should expect from our study of the oxydases of the vegetative 

 members of P. sinensis that which is lacking from recessive white flowers 

 is not the oxydase forming factor but the factor for chromogen produc- 

 tion. Treatment of the petals with benzidine demonstrates that this 

 expectation is correct, for, as indicated already, the result of the treat- 

 ment is a well marked oxydase reaction in both epidermis and veins 

 (Plate XIX, Fig. -5). Whence we conclude that since the corollas of 

 recessive whites contain both epidermal and bundle oxydases their 

 lack of colour is due to the absence of the factor for chromogen pro- 

 duction. Of all the varieties the flowers of which we have examined 

 only those belonging to three categories show any departure from the 



