1026 



less that the aberrant ratio of the miiiiber cannot be explained by 

 this means alone ; some other cause must also be present which 

 acts in the same direction. 



I have indeed succeeded in demonstrating this second cause of 

 the deficiency of white-flowering plants. It is connected with the 

 average number of seeds which are formed in the fruit of flax. 

 The flax-fruit may contain a maximum of ten seeds. The average 

 number, however is distinctly less, and in the white variety it is, 

 as I repeatedly observed, in general still smaller than in the blue one. 



Now when the average number of seeds in the fruits of the 

 heterozygotes, which contain both seeds of while- and of blue-flowering 

 plants, is smaller than in the blue P-i'ovm, then the assumption is 

 plausible, that this is caused, by the formation of relatively fewer 

 seeds of white-tlo wering plants. If this seed is sown a progeny arises 

 with a deüciency of white-flowering plants. 



The investigation was however not so simple in this case. In 

 conti-adistinction to the foregoing it was found that in the crossed 

 varieties the fruits of the white flax had on the average even a 

 greater numbei' of seeds than those of the blue Egyptian flax. In 

 330 fruits of the white flax the number of seeds amounted to 2412, 

 an average of 7.31, while in 219 fruits of the Egyptian flax, there 

 were 824 seeds, an average of 3.76. In the white variety the average 

 number of seeds, is therefore almost twice as great as in the blue. 



Now the seed of Egyi)tiau flax is, however, ninch larger than that 

 of the white flax and comparisons of diirerenl varieties had already 

 convinced nie before that the average number of seeds is closely 

 connected with the size of the seed and in such a way that in 

 varieties with large seeds the average nnmber is in general smaller 

 than in varieties with small seeds. It is therefore possible, that in 

 the white flax there is indeed a tendency to produce a smaller 

 mimber of seeds than the average number of the Egyptian flax, 

 but that this tendency is not revealed at all, because the diiTerence 

 in size of the seed of the two varieties is accompanied by a much 

 greater difference in number in the opposite direction. In order 

 to make tliis out it is necessary therefore to eliminate the influence 

 of size. This is indeed possible in the case under consideration. My 

 earlier investigations ^) have shown that the difference in size between 

 the seed of Egyptian flax and that of Linum angicstif o Hum is csiused 

 by several factors. Consequently there arise in the second generation 

 forms differing in the size of the seed, intermediate between that of 



1) Das Verhalten flukluierend variiereuder Merkiiiale bei der I^astardieiung. Ree. 

 d. Trav. bol. Néerl. Vul. 8, 1911, p, 212. 



