F. Keeble and E. F. Armstrong 295 



D. The Oxydases of Geranium sanguineum. 



We may cite further evidence in favour of the major proposition 

 that the two factors for pigment formation are chromogen and oxydase. 

 As has been shown by genetical research, with such plants as Sweet 

 Peas (Bateson, 1906) and Orchids (Hurst, 1909), so we show by means 

 of chemical methods that albino races are of two kinds. The white 

 flowered races of Sweet Peas (Lathyi-us odoratus) and of culinary peas 

 {Pisum sativum), so far as we have examined them, all contain ox}'dase 

 of the type present in the coloured forms and hence the lack of colour 

 in these races of the two species is due to lack of chromogen. With 

 respect to the former species, however, it should be remarked that we 

 have not yet had an opportunity of investigating thoroughly the two 

 types of white flowered plants which yield when crossed with one another 

 a coloured Fi. So far as our observations go at present we have found, 

 neither in round-pollened nor in long-pollened albino Sweet Peas, no 

 flower from which oxydase is absent. It maybe that further search will 

 discover such flowers or it may of course be that the factors determining 

 pigmentation are other than those suggested above. In any case the 

 evidence provided by the albino of another species of plants. Geranium 

 sangidneum, is favourable to our hypothesis. The petals of the flower 

 of the purple type of G. sanguineum give with benzidine a definite 

 epidermal oxydase reaction and a yet more marked reaction for bundle 

 oxydase. The pure white petals of the albino variety give with the 

 same reagent a distinct bundle reaction, but no epidermal reaction. 

 Hence this white form is either a dominant white or a true albino of 

 the second type, namely one which owes its whiteness to deficiency of 

 oxydase in the epidermal cells. Although we have been unable, owing 

 to lack of material, to determine absolutely to which of these categories 

 it belongs, the fact that the bundles give a definite oxydase reaction 

 appears to indicate that the white G. sanguineum is not a dominant 

 white. 



The intermediate form, Geranium lancastriense, which is characterised 

 by a flower of pale flesh colour with darker pink veins stands midway 

 between the type and the albino ; for although it gives no or at most a 

 very slight oxydase reaction in the epidermis of the flower, it gives a 

 very distinct (violet-brown) bundle reaction. 



It would appear therefore from the observations on ever-sporting 

 races Primida sinensis and Dianthus barbatus and on the albino forms 

 of Sweet Peas and of Geranium sanguineum that two types of albino 



