1()2<S 



of the aberrant numerical [)ropürlion. Altliongh the deficiency is 

 not wliollj accounted for by the two causes, jet I do not bebeve 

 that it is necessary to postulate a third cause for the absence of 

 white-flowering plants. 



In the foregoing it has been assumed in all calculations that the 

 heterozygous blues behave as homozygous. I came to this conclusion 

 because of an investigation of the progeny of blue-tlowering F^ 

 individuals. Normally ^ 3 of the blue-flowering F^ plants are homo- 

 zygons and Vs heterozygous. If, however, heterozygotism were to 

 exercise an influence, it would be noticeable in the number of seeds 

 and in their germinating-power. In proportion to the seeds which 

 are Iiomoz}gous blue for the colour of flower there should be from 

 h\bi-id plants a smaller number of heterozygotes formed and this 

 seed should moreover have less germiuating-power. The result 

 would be that in the succeeding generation too few heterozygous 

 blue-flowering plants occurred, which would be evident fron» the 

 investigation of the j)rogeny. 



This inquiry now showed that out of 41^ 7\ plants, 13 were 

 homozygous and 30 heterozygous. Instead of a deficiency in hetero- 

 zygotes this number is even greater than it should be theoretically. 

 Although the figures are small, nevertheless I think that it may 

 be concluded, that the heterozygous blue plants behave in the same 

 way as homozygous ones. 



As well as in the crossing l>etween the blue Egyptian flax and 

 the white flax described above, I observed similar aberrant numerical 

 proportion in some other crossings between white- and blue-flowernig 

 varieties. In the crossing between Vilmorin's white flax mentioned 

 above and the blue flax commonly cultivated in Holland 318 white- 

 flowering and 1312 blue-flowering plants were obtained in F^, that 

 is in the proportion 0.78 : 3.22. The deviation here observed. 

 =F 0.22 is even slightly greater than that found in the previous 

 crossing. The deviation here must also consist in a deficiency of 

 white-flowering plants, brought about by the causes mentioned above. 

 This is clear from the following. In 211 fruits of the common blue 

 flax the number of seeds amounted to 1851, an average of 8.78; 

 whilst the average for the white flax was seen to be 7.31. The 

 blue flax has therefore a higher average number of seeds in the 

 fruit. These two values are directly comparable because the size of 

 the seed is about the same. In connection with this, the average 

 number of seeds in the fruits of F^ lies between these two values 

 and amounts to 8.38. In these fruits therefore, in proportion a some- 

 what smaller number of seeds is produced for white-flowering plants 



