Harris, A quantitative study of the factors influencing etc. IX 



be regarded as fairly smoothing the observed means, but in NH 

 there is clear evidence of non-linearity. This is also, as already 

 noted, especially conspicuous in the diagram. 



III. Discussion and Summary. 



This paper, which is one of a series dealing with 

 the physiology of seed production, embodies databearing 

 on the problem of the factors determining the weight of 

 the bean seed. 



This first part based upon a series of weighings of 

 about 23,000 seeds drawn from five cultures of three dif- 

 ferent varieties, deals solely with the problem of the 

 dependence of seed weight upon the characteristics of 

 the pod. Other factors will be discussed later. All 

 general discussion of literature and of observations is 

 reserved. The present summary deals only with the find- 

 ings as to facts in the phase of the problem under con- 

 sideration. 



The influence of the characteristics of the pod upon 

 the weight of the seed is easily measured in terms of the 

 correlation between the two variables. That between 

 number of ovules per pod and weight is low. Indeed, 

 both positive and negative values of the coefficient occur, 

 and the rate of change in weight associated with a Va- 

 riation of one ovule in number of ovules per pod ranges 

 only from —.0071 to + .0Q52 grams. Thus number of ovules 

 formed is practically negligible as a factor influencing 

 seed weight. 



For the relatioship between number of seeds matured 



per pod and seed weight the results are more consistent. 



In all cases, the weight of the seeds decreases as the 



number of seeds per pod increases; but the correlations 



are low throughout, averagingonly — .096. The change in 



absolute seed weight for an increase or decrease of one 



seed is only .0055 grams. 



-^ , , • , ! seeds per pod, 



For the relative number of seeds,- -=- — j- 



ovules per pod, 



the correlations are even lower thanfor absolute number, 



averaging only — .073. 



The chances of an ovule developing into a see-d are 

 correlated with the position which it occupies in the 

 pod — the percentage of development increasing from 

 the base towards the stigmatic end. In small pods, the 

 rate of increase may be fairly regulär, but in largerpods 

 it falls off towards the distal end, where the f ecundity 

 may be even lower than in less distal regions. 



The weight of the seed is also postively, but not 

 highly, correlated with its distance from the proximal 



