138 Phi/siologieal Pre-determination 



decreased with the increasing age of the plants, and the autlior conchided 

 that ths result depended upon the larger quantity of reserve materials 

 in the heavier seeds. In the case of perennial plants the original advan- 

 tage of the heavier seed is araduallv lost. 



C. Conclusion. 



The genera] conclusion to be drawn from this review of the literature 

 is that the effect of parental conditions upon the seed in determining 

 its subsequent course of development may be considerable. 



The environmental conditions operating upon the seed whilst on 

 the parent plant may be divided into two classes, viz. : 



(1) The environment of the seed itself, in other words, its position 

 on the parent plant. The effect of the position of the seed upon the 

 parent plant is most clearly reflected in the size of the seed and is inde- 

 pendent of external conditions. The balance of evidence is in favour of 

 the conclusion that larger seeds give rise to more vigorous plants and a 

 better yield. 



(2) The environment of the parent. Here again differences in the 

 size of the seed are the only effects which are visible in the seed itself, 

 but there is evidence that environmental conditions which affect the 

 parent may also markedly influence the subsequent course of develop- 

 ment of the seeds produced. So that effects which become visible in one 

 generation may have to be traced back to the external conditions which 

 operated in a previous generation. 



The question of the pre-detcrmining effect of parental conditions is 

 much complicated by the ever-present possibility of hereditary factors 

 being concerned, and in most cases the facts have so far been almost 

 entirely considered from the point of view of heredity alone. In the 

 following sections, in which we shall deal with the pre-determining 

 effect of the conditions operating during harvesting, dormancy (storage), 

 and germination respectively, the difficulty of interpreting the results 

 will not be complicated by the intrusion of the question of heredity. 



{To he coniinned.) 



