14 Flower Colour and Characters of the Opium Poppy 



both capable of developing a purple colour; but such a conclusion is 

 not supported by any other evidence. If, for instance, we adopt this 

 supposition, of the extracted purples from those families in which both 

 Group III and Group IV colours occur, 7 should be pure, 4 should 

 give purples and whites in the ratio 3:1, and 4 the same colours in 

 the ratio 15 : 1. Actually, of the purples bred on for another generation 

 from these families, 13 have proved to be pure, 20 have given purples 

 and whites in the proportion 3 : 1, while none have given the ratio 15:1. 

 Nor have we observed in any of the numerous families raised from 

 impure purples 'a single instance of a 15 : 1 ratio. 



A third explanation, namely that the two factors M and L are alter- 

 native, occupying identical loci in the chromosome ^ is also ruled out of 

 the results we have recorded. The form PPML, which alone carries 

 the two factors on this supposition, could not give Group II and V 

 colours. 



For the present we are unable to offer any completely satisfactory 

 explanation of the phenomenon here described, and further work will be 

 necessary before such an one is obtained. We have already referred to 

 the uncertainty which attaches to the form F^C. A more complete 

 understanding of the nature of this colour may afford the explanation at 

 present lacking. 



Other colour factors. 



In describing the colour groups we noted that, in most cases of the 

 .pure colours, each form is in reality dual. On the one hand is the 

 standard form and on the other that which develops a distinct crimson 

 appearance especially marked when the petal is viewed by transmitted 

 light. Thus the pink occurs as the standard, P, and the crimson-pink 

 P (G) ; the RP as the standard and the crimson CP; the MP and PL as 

 standard and as the crimson MPG and PLC; the RB as the standard 

 and the crimson CB and, finally, the red as the standard R and the 

 crimson G. In certain families the standard, and in others the crimson 

 form occurs in a condition of purity. In other cultures, again, a complete 

 series ranging from the typical standard to the typical crimson is 

 obtained. It would appear that the crimson colour is due to a factor 

 of the nature of an intensifier which is activated both by the P and M 

 factors. It is possible that two factors are involved, but the evidence is 

 as yet insufficient for a definite decision to be given on this point. 



1 See Morgan, The Mechanism of Mendelian Heredity, Chap. vii. 



