E. R Saunders 317 



should expect a population to behave if it was composed of double- 

 throwing and non-double-throwing individuals of the same race breeding 

 indiscriminately together. Under these conditions we should expect 

 that some individuals would yield an excess of doubles, and that others 

 would breed true to singleness, and that in the latter case the succeed- 

 ing generations would be homogeneous and would behave like their 

 parents. Further, that other individuals though yielding a mixture 

 of singles and doubles would give an excess of singles. The plants 

 yielding an excess of singles would be cross-breds due to cross-breeding 

 between the eversporting and the true-breeding single, and each 

 succeeding generation of their descendants, if self-bred, would prove 

 heterogeneous, and give again true-breeding singles and singles giving 

 a minority of doubles. 



From the facts detailed in the preceding pages it therefore seems 

 reasonable to suppose that in the case of the sulphur-white and the 

 various sap-coloured strains employed the samples of commercial seed 

 investigated were harvested from homogeneous populations composed 

 of eversporting individuals only. That in the case of the white and 

 cream races the populations from which the seed was collected included 

 pure-breds and cross-breds, some of the pure-breds being eversporting, 

 some true-breeding. A sample sowing in the case of these two strains 

 might therefore very well produce all three types of single, as indeed 

 appeared to be the case with the cream, where A, B, H, I and J ap- 

 peared to be eversporting, C, D, E and F true-breeding, L and probably 

 K either cross-breds or the oflFspring of cross-breds. The remaining 

 plants, viz. G, M and X, were also producing doubles, but the evidence 

 is insufficient to determine whether they were pure-breds or cross-breds. 

 This explanation indeed appears to be the only one tenable, for the 

 facts which have been given may be taken to put out of account any 

 question of accident in the handling of the seed before it was supplied, 

 or of the frequent occurrence among eversporting forms of pollen grains 

 carrying the single character. 



III. Proportion of doubles obtained from the eversporting strains 

 when self-fertilised or inter-crossed. 



i When self-fertilised. (For details see Tables III, VI, VII, and 

 VIII.) 



As previously stated (Report III, p. 45) eversporting individuals, 

 when self- fertilised, usually give an excess of doubles. It may be noted 



