External Conditions and Hereditary Values. 485 



zvith d5 to 75% syueotylous offspring, and could there- 

 fore be brought back in one or two generations to the 

 highest point attained by the original race. It is there- 

 fore far removed even from the slightest semblance of 

 a half race. 



How far, in the case before us, selection could lead 

 in the course of years can, of course, only be surmised. 

 But the sunflower is not a suitable species for the con- 

 tinuation of these experiments, on account of the risk 

 of occasional pollen grains of the ordinary sort being 

 brought by insects from distant gardens ; for under these 

 conditions selection would promptly extract a half race 

 which would be the result of hybridization and not of 

 selection, and artificial fertilization in the sunflower is 

 beset with very great difficulties. 



§ 13. THE INFLUENCE OF EXTERNAL CONDITIONS ON 



HEREDITARY VALUES. 



In these cultures my practice has been, first to record 

 the seedlings in the pans and then to plant them out into 

 pots with well manured soil, from which they were trans- 

 planted to the beds in June. Here the plants stood at 

 distances of over half a meter apart. As soon as axillary 

 buds became visible they were removed, and only the 

 terminal head was allowed to flower. Fertilizati(^n was 

 left to insects, for my sunflowers do not set seed without 

 crossing. As soon as the seed is ripe, T cut off the whole 

 head in order to collect and clean the seed. 



The question presents itself, does this method of cul- 

 ture exert any considerable influence on the proportions 

 of syncotyls? In order to provide an answer I have in- 

 stituted a number of subsidiarv cultures in different vears, 



