176 ANTHOCYANINS AND GENETICS 



Varieties of stem-colour. 



Anthocyanin may be entirely absent when the stem is green. This 

 condition is associated with recessive white flower-colour (occasionally 

 dominant white, i.e. 'Pearl'), or with pale colours of which the deepest 

 is 'Reading Pink,' and no flower-colour deeper than 'Reading Pink' 

 is ever found on plants devoid of anthocyanin in the stem. 



There may be faint colour in young leaves and petioles associated 

 with pale flower-colour. 



There may be pigment at the bases only of petioles and pedicels, 

 associated with 'Sirdar' flower-colour. 



The stem may be fully coloured with purplish-red sap, either light 

 (dilute), or deep, associated with full flower-colours, i.e. salmon-pink, 

 crimsons and magentas; but whereas light magentas and crimsons 

 can be borne on both light- and deep-stemmed plants, the deepest 

 magentas and crimsons can only be borne on deep-stemmed plants. 



The stem may be coloured with pure red sap associated with ' Orange 

 King' flowers. 



The stem may be coloured with blue sap associated with blue flowers. 



Hence the direct relationship between stem and flower-colour may 

 be summed up as 



Recessive whites and green stem. 



Pale flower-colours and green, or faintly coloured, stem. 



Full flower-colours and full-coloured stem (and of these deep flower- 

 colour and deep stem). 



True red ('Orange King') flower-colour and true red stem. 



Blue flower-colour and blue stem. 



Factors (stems). 



Colour in both flowers and stems can be produced by two or more 

 complementary factors. Keeble & Pellew (541) obtained an Fj with 

 magenta flowers from two whites. As regards stem, there is no case 

 of colour from mating two greens, but plants heterozygous for colour 

 in the stem have given 9 coloured : 7 green stems. 



Slight colour in the stem is due to the factor Q, which is dominant 

 to complete absence of colour. 



The difference between full colour and faint colour is due to a 

 dominant factor, R. 



The difference between 'Sirdar' and full colour is due to a factor, 



