1029 



than for hluc-tlowcriiig' ones. The i4ei'iniii;iliii;j,-|t()\vei' al.so slinws a 

 difFereiice capable of e\plainiii<>- a deficiency in while-llo\vei'iii<2; plants, 

 because fhe comnion l)liie flax that was used in my experiments, 

 {j,ei'minates very well. Less than J"/,, fails, as in the blue Egy|)tian 

 flax, whilst the white flax, as has been said, shows a loss of 11,5) "/„. 



Besides the white flax from the firm of Vilmorin still another white 

 variety was crossed with the two blue forms mentioned. This was 

 cultivated as a pure line from a white-flowei'ing form grown in the 

 province of Friesland. 



By crossing this white with the blue Egyptian flax thci-c were 

 obtained in h\^ 60 white-flowering and 214 blue-flowering plants, 

 that is in the proportion of 0.876 : 3.124 with a deviation of 

 + 0.124. 



The crossing between the last mentioned white flax and the common 

 blue one gave 30 white- and 104 blue- (lowering individuals, a 

 proportion of 0.895 : 3.105 with a deviation of + 0.105. 



lu both cases a deficiency in white-flowering ])lauts appeared in' 

 F^ . Although the number of observations is not great, I think it 

 may nevertheless be concluded that we are here dealing with the 

 same phenomenon, because in comparison with the blue-flowering 

 varieties this white form also has a lower average number of seeds 

 and an inferior germinating-power. The differences are however not 

 so great as with the white flax obtained from Vilmorin. 



The question now arises how the lesser luunber of seeds and (he 

 lesser germinating-power of the seeds of the white-flowering variety 

 are caused. With respect to the number of seeds it is possiltle that 

 the cause lies in the number of gametes formed. Normally in Fj^ as 

 many gametes without t''e factor for blue should be formed as those 

 possessing this factor. Should there however be fewer gametes formed 

 in which the factor for blue is absent, then there will be after 

 fertilisation not only a relatively smaller number of homozygous 

 whites but also fewer heterozygous ones and F^ will necessarily have 

 a deficiency in heterozygous blues as well as in whites. 



As 1 have shown, this is not the case, there is here no deficiency 

 in heterozygous plants. Therefore the cause does not lie in a differing 

 number of the two kinds of gamefes and can only be sought in 

 phenomena at or afler fertilisation. It may be that the union of two 

 gametes, both devoid of the factor for blue, happens less easily so 

 that in some cases no fertilisation takes place. Or it is also possible 

 that the two gametes do unite and that a zygote is produced, but 

 that the embryo already dies off in the first stages. In both cases 

 there will be a deficiency of seed for white-flowering plants. Some- 



