Inconstancy of Improved Races 771 



might perhaps best be considered to end with 

 the beginning of the resting stage of the ripe 

 seed. Hence it is clear that the variability of 

 seed-propagated annual races has a wider range ' 

 than that of perennials, shrubs and trees. At 

 present it is difficult to discern exactly the part 

 each of these two main factors plays in the 

 process. Many indications are found however, 

 that make it probable that embryonic variability 

 is wider, and perhaps of far greater impor- 

 tance than the subsequent partial fluctuations. 

 The high degree of similarity between the single 

 specimens of a vegetative variety, and the large 

 amount of variability in seed-races strongly 

 supports this view. The propagation and multi- 

 plication of the extremes of fluctuating varia- 

 bility by means of seeds requires a close 

 consideration of the relation between seedling 

 and parent. The easiest way to get a clear con- 

 ception of this relation is to make use of the 

 ideas concerning the dependency of variability 

 upon nourishment. Assuming these to be cor- 

 rect in the main, and leaving aside all minor 

 questions, we may conclude that the chosen 

 extreme individual is one of the best nourished 

 and intrinsically most vigorous of the whole 

 culture. On account of these very qualities it 

 is capable of nourishing all of its organs better 

 and also its seeds. In other words, the seeds 



