Harris, A quantitative study of the factors influencing etc. 7 



be exercised in discussing, except upon a groundwork of extensive 

 quantitative data, questions of the physiology of nutrition or of the 

 "causes" of the so-called "fluctutating variability". 



The influence of position in the pocl. 



The possibility of an influence of the position of the seed in 

 the pod upon the weight that it attains is suggested by the general 

 belief that the ovules near the ends show a higher mortality. The 

 causes of this failure are quite unknown. There seems little ground 

 for the assumption that the end seeds have not room to develop. 

 The fact that development is not equally frequent at both ends of 

 the ovary evidences strongly against this view. More probably, 

 the factors are opportunity for fertilization and Variation in plastic 

 materials. If distance from the stigma affects time of fertilization, 

 or if distance from the pedicel influences the chances of obtaining 

 seed-building substances, these factors should theoretically be re- 

 corded in the weights of the seeds as well as in the relative numbers 

 developing in each of the several positions. 



For the series here considered records of the position of all 

 seeds developing as well as of those weighed have been kept. It 

 seems worth while to consider the data. It is idle to ascertain 

 the percentage of development or weight at maturity of ovules in 

 any position in a sample of pods of various numbers of ovules. 

 The pods must be sorted into sub-groups according to the number 

 of ovules which they contain. It might be desirable to sub-sort 

 the ovule classes according to the number of seeds matured per 

 pod, but for our present purposes and on the basis of the available 

 data this extra refinement is out of place. 



The relationship between the position of the ovule in the 

 pod 1 ) and its chances of development is shown in the most Con- 

 densed manner by a graph, Figure 2. 2 ) 



From this diagram, it is perfectly clear that: 



a) The chances of development are much better for ovules 

 situated towards the distal than those towards the proximal end 

 of the pod. 



b) For pods with a small number of ovules (three), the po- 

 sition of maximum development is generally at the tip. In pods 

 with a larger number of ovules the rate of increase in percentage 

 of development is not linear, and there may be a decided falling 

 off at the distal end of the pod. 



') By "position in the pod", we understand the serial order from the 

 proximal to the distal end — the firwt ovule being numbered 1. 



2 ) In the five diagranis, the percentage of the total ovules formed which 

 develop into mature seeds in any position in the pod is shown by the heights 

 of the circles on the scale indicated in part at the side of the graph. The 

 position of the ovule in the pod is indicated by the shift from left to right 

 on the base line. Thus, the reader, with a little trouble (unavoidable, if the 

 data are to be presented in a very Condensed form) may determine with mo- 

 derate accuracy the percentage frequency of development for any position in 

 any of the chief classes of pods. 



