THE DOUBLE STOCK, ITS HISTORY AND BEHAVIOUR. 471 



the time of planting out than their sister doubles of the same sowing, 

 then a choice of the more vigorous seedlings would naturally lead to a 

 certain selection in favour of the doubles at the time of bedding out 

 and might account for the unexpected results quoted above. 



Experiments recently undertaken with the object of testing this 

 view clearly point to the correctness of this latter explanation. In 

 191 1 I was able to harvest seed myself from some of the few single 

 individuals occurring that year in this strain (see number quoted 

 above). Care was exercised to bring every seedling, if possible, to 

 maturity, and none was discarded. The results entirely preclude the 

 idea that this particular strain is in any way exceptional as regards the 

 output oj doubles. As has been set forth in earher papers, the expecta- 

 tion for double-throwing strains is a definite, though slight, excess 

 of doubles, the proportion being probably 9 doubles to 7 singles, 

 or possibly only 8*5 doubles : 7-5 singles, i.e., not quite 57 per 

 cent, on the one view, rather more than 53 per cent, on the other. 

 Now, whereas a proportion of only 30 singles to 180 doubles, or nearly 

 86 per cent, of doubles, were recorded in the College garden in 1913 

 (see above), I obtained in my culture of the same year from seed 

 from the same source as many as 185 singles to 224 doubles, or about 

 55 per cent, of doubles, a result entirely in accord with the usual 

 expectation. The evidence, in fact, points to this being a perfectly 

 normal case, both as regards total output of doubles, and also as 

 regards absence of localization at either end of the pods of the double- 

 producing seeds. For in order to test this latter possibility (a view 

 originally put forward by Chate which, however, appears not to be 

 borne out by the facts) a number of pods were halved across, and the 

 seeds of the upper and lower ends sown separately ; from both these 

 sets the same slight excess of doubles was obtained as from the whole 

 pods.* We may then conclude that the actual output of doubles in 

 this particular strain is the same as that of all the other strains 

 previously investigated, and amounts on the average to not more than 

 57 per cent. Where, then, an abnormally high proportion of doubles 

 appears in the beds, we must suppose some selective action coming 

 into play at a later stage than seed production. This selection, as 

 will shortly be apparent, was exercised in this case, though without 

 intent to that end, at the time of planting out, the very natural choice 

 for the beds of the most vigorous young plants resulting in the un- 

 intentional saving of more doubles and fewer singles than would have 

 been obtained from an equal number of the same batch of plants 

 taken at random. That young double Stocks grow more vigorously 

 than the singles I have long suspected, but opportunity for obtaining 

 a considerable amount of evidence on this point was not found until 

 this year. This difference in rapidity of growth is most easily seen if 

 the young plants are raised in pots, a small number of seeds only bemg 



* See also in this connexion " Further Experiments on the Inheritance of 

 ' Doubleness' and other Characters in Stocks." Saunders, Journal oj Genetics, 

 vol. i. No. 4, p. 363, 191 1. 



