R P. Gregory 96 



collar and bases of the petioles (Plate XXX, tig. 4 ; Plate XXXI, 

 figs. 44, 45). The degree to which colour is developed in the stem 

 may therefore be taken as an index of the limits within which the 

 colour of the flowers will be confined. All the red-stemmed whites 

 which I have examined were found to be white in virtue of factors 

 which inhibit the development of colour in the flower, though their 

 range of action does not extend to the stem'. 



A. Stem-Colours. 



Various types of coloured stems are illustrated in Plate XXX. The 

 plants shown in figs. 1, 2, 4 and 5 all possess, in varying degrees, the 

 common purplish-red sap. Sap of this colour is present in the stems 

 of all the races which have the usual magenta or red flowers, and 

 though there are, no doubt, minor dififerences in the tint in diflferent 

 races, it is scarcely possible in practice to make any distinction between 

 forms which differ in so slight a degree. There are, however, two kinds 

 of flower-colour which are associated with distinctive stem-colours; 

 in the races which have blue flowers the stem has a corresponding 

 colour, as compared with that of the commoner purplish-red types; 

 while the clean red stem, shown in fig. 3, is, so far as my observations 

 go, limited, in the fully coloured form, to the strain known as " Orange 

 King" (fig. 8). 



In coloured stems the red sap may be distributed over the whole of 

 the stems and petioles (Plate XXX, figs. 1 and 2), or it may be developed 

 only in certain regions, the other parts being green. Fig. 4 shows a 

 form in which the colour occurs only in the collar and bases of the 

 leaf and flower stalks ; in plants with coloured flowers this type of stem 

 is always associated with a peculiar distribution of the flower-colour 

 which is characteristic of the strain known as "Sirdar" (Plate XXXI, 

 figs. 44, 45). In fig. 5 there is represented a lower type of stem-colour, 

 in which the colour is most pronounced in the young petioles. It is 

 often only faint, and is sometimes scarcely discernible in the older leaf 

 stalks, so that the character is somewhat elusive. It is dominant to 

 the complete absence of sap-colour exhibited by " Snowdrift " (fig. 7), 

 but the discrimination between the various types in F^ is ditficult, 

 the more so since " Snowdrift " brings in a factor which reduces the 

 apparent colour to a minimum. 



' Keeble and Pellew record the existence of a recessiTe white on red stem {Joum. 

 Genetic*, Vol. i. 1910, p. 1). 



