THE ABORTION OF OVULES 347 



as occur indicating only a slight increase in length of the pod 

 as a result of a great increase in the number of seeds, and 

 affording but scant basis on which to found an explanation 

 of the differences in length between the pods of these two 

 species. Thus the rule which we would apply to explain 

 the differences between the two species largely fails when we 

 apply it to the individuals of one of them ; and we are 

 accordingly debarred from using this argument in explaining 

 the fact that the long pod of Vicia sativa has many seeds 

 and few failures and the short pod of V. sepium many failures 

 and few seeds. 



Using legumes of the same set of plants of Vicia sepium 

 and selecting a few at random, 1 found that a pod where all the 

 twelve ovules had developed into mature seeds, a very rare 

 event, had the same length as a pod where only five seeds had 

 matured. So again a four-seeded pod and a nine-seeded pod 

 had the same dimensions. In the aggregate, however, there 

 is a tendency in the pod to increase its length as the seeds 

 increase in number ; but it is quite insufficient to explain the 

 difference in length between the pods of these two plants. 

 Thus ten pods of Vicia sepium containing four or five seeds 

 had an average length in the dry state of 30 millimetres, whilst 

 five pods containing from seven to twelve seeds had an average 

 length of 35 millimetres. Here the doubling of the number 

 of seeds only resulted in the increase of the pod's length by 

 one-sixth. 



There are two other points to notice in connection with 

 the legumes of these two species of Vicia. In the first place, 

 it will have been remarked that the aborted ovules, or more 

 correctly speaking the seed-failures, are complemental to the 

 matured seeds, the two going to make up the complete set of 

 the original ovules. This is well brought out in the results 

 tabulated below ; and on referring to the general table for 

 ovular abortion in fruits given later in this chapter, it will 

 be seen that this principle is characteristic of fruits of all 

 kinds. 



