146 REPORT OF THE CONFERENCE ON GENETICS. 
the four corresponding bi-colours, white, and cream. Plastid colour 
bebaves as a recessive character. Hence white and self sap-colours are 
dominant over cream and bi-colours respectively. The sap-colours occur 
in the proportion of 9 purple : 3 red : 8 plum : 1 copper; and among the 
non-sap-colours the white are to the cream as 3: 1.* The appearance of 
this sap-colour series is due to the presence in the white parent of two 
independent factors, neither of which can be detected unless C and R are 
both present, viz. (1) a factor (B) which turns the colour produced when 
C meets R blue (in the absence of B the colour is red); and (2) a factor 
which produces the modified shades, copper and plum, in place of the 
full red and purple. Both these factors are absent in cream, for cream 
glabrous x red glabrous gives red F, and only the full colours in F, ; 
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SS CRHESS CRHk RS CRUSE CREE 
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Fie. 1.—ScuemMe or F, From WHITE Fic. 2._ScuemE or F, From CREAM 
GuLaBrous x CREAM GLABROUS GLABROUS x SAP-COLOURED GLABROUS 
(CrHK x cRHK). (cRHK x CRHk). 
Ratio of hoary to glabrous = 9. 7. Ratio of hoary to glabrous = 9: 7. 
Ratio of coloured to uncoloured = 9: 7. Ratio of coloured to uncoloured = 3 : 1. 
Each square represents an individual, and the lettering shows its composition. 
Horizontal hatching shows sap colour in the flower. Oblique hatching 
indicates hoariness. When Cand R are both present, the flower is coloured. 
When H and K are also present, the plant is hoary ; it is glabrous when one 
or more of these four factors is absent. 
whereas white glabrous x red glabrous gives purple F, and both the full 
and the modified colours in F,. 
The pale shades occurring in certain other glabrous types, such as 
flesh and pale purple, which are dominant over the full colours, are 
probably due to the presence of yet another factor. 
It appears, however, that we have not even yet exhausted the list of 
factors which may affect the flower-colour in cases such as those which 
we have been considering. There is some evidence that when the parents 
are individuals which yield both single- and double-flowered offspring, 
there may be a certain amount of coupling between the character of the 
flower and some of the colour factors. One strain of ten-week stocks, 
* In certain cases, however, a deficiency of creams was observed. Whether this 
is due merely to the late-flowering habit of the creams or to a further complication is 
not yet clear. 
