320 Douhleness in Stocks 



As shown in an earlier account* and in the accompanying Tables, 

 niatings between two double- throwing parents invariably gave doubles 

 in the next generation. We should expect, unless other complexities 

 are indicated, that the results in such matings will be the same as when 

 either c?-parent is self-fertilised, and that the proportion of doubles 

 obtained from a cross will, as in the case of self-fertilisation, furnish 

 an index of the proportion of double-carrying ovules produced by the 

 d-seed-parent. 



Altogether 1673 plants were raised in the present experiments in 

 Fi, from 60 matings between various rf- strains, representing an 

 equivalent number of ovules from 45 c?-seed-parents ; or, if we exclude 

 all matings in which the cream plants K and L were employed on the 

 ground of suspicion as to their purity, we have 1343 F^ individuals 

 from 50 matings in which 37 cZ-seed-parents were used. If all these 

 50 families are summed together, we get a total of 586 singles and 

 757 doubles, or almost exactly 7 s. : 9 d.^ A certain number of these 

 c?-seed-parents were also self-fertilised, and we are therefore able to 

 compare the effects of own pollen versus foreign pollen on identical 

 individuals. 



The results were as follows: 



From crossing 15 individuals with pollen from 



d-individuals of other strains 248 singles 298 doubles 



where a ratio of 7 s. :9d. would give ... 239 ,, 307 „ 



or 7-5 8. : 8-5 d. would give ... 256 „ 290 



From self-fertilisation of these same individuals 437 ,, 539 ,, 



where a ratio of 7 s. : 9 d. would give ... 427 ,, 549 ,, 



or 7-5s. :8-5d. would give 457| ,, 518^ „ 



Again, 35 matings were made, in which jPj from two eversporting 

 forms was crossed back with one of the eversporting parent types. 

 If the 35 F^ families are summed together, we get a total of 



421 singles and 505 doubles, 

 where a ratio of 7 : 9 would give 



405 singles and 521 doubles, 

 and a ratio of 7*5 : 8'5 would give 



434 singles and 492 doubles. 



1 Rep. Evol. Committee, IV, 1908, Table II. p. 40. 



2 In certain cases the results obtained from one fruit were unexpectedly divergent 

 from those of another, and a considerable sowing had to be made before an indication of 

 the probable ratio was obtained. But where large numbers were recorded the results 

 appeared sufficiently uniform to justify the inclusion of the whole series in one total 

 as above. 



