1061 
curve for the breadth which extends from the minimum of the 
narrowest to the maximum of the broadest form, with the summit 
near the average of the two P-forms. Here, however, the whole of 
the second generation gives a curve for the breadth, which indeed 
extends from the minimum of the narrow white to the maximum 
of the Egyptian flax, but which shows two summits between these. 
Since one part of the curve towards the minimum with one of the 
summits is formed by the white, and the other part with the other 
summit by the blue F-individuals, it is evident that there is here 
an interdependence between breadth and colour. Yet this relation is 
not simply, that blue colour is associated with broadness, because 
the same factor or factors simultaneously cause broadness and blue 
colour, or because the factors for broadness and those for colour 
are completely coupled, as is apparently the case in the crossing 
of the ordinary blue flax with the narrow-petalled white. If this 
were the case, then all the white offspring would have to show 
the type of broadness of the narrow-petalled white flax, and all 
the blue descendants the broadness-type of the Egyptian flax. 
This is not so, however, for white petals occur, which are broader 
than the white P-variety and blue ones, narrower than the blue 
P-variety. In an attempted explanation we might assume incomplete 
coupling of the factors for broadness and for colour, leading to 
very complicated relationships. This is, however, a great disadvantage 
and we are induced to search for another explanation of this pecu- 
liar interdependence between the two characters, which here presents 
itself. Now previous experiments on the crossing of these varieties of 
flax have demonstrated *) the presence of various factors and it is a 
knowledge of these and of their action that enables us to give a satis- 
factory explanation, not only of the phenomena attending the last 
mentioned crossing, but also of the fact, that in the various crossings 
the behaviour of the breadth and the connection between breadth 
and colour are so varied. 
Previously it was shown, that the genotypic composition of the 
common blue and of the Egyptian flax for the colour of the flower 
is represented, in the common blue and in the Egyptian flax, by 
the formula AABBCC, in the common white by AABB and in the 
narrow-petalled white by AACC. The factors B and C acting 
conjointly, cause the blue colour, but are separately unable to produce 
a blue colour. Furthermore B and C exercise an influence on other 
characters, as was previously discussed in detail. A is an intensification- 
factor for the colour, but remains out of account here. 
1) Le. vol. XII, 1915, p. 217. 
