346 STUDIES IN SEEDS AND FRUITS 



millimetre in size, they all attain a size rather less than a 

 millimetre. It is after this stage that the differences between 

 the two fruits are displayed, and in describing them I will make 

 use of my average results. In the case of Vicia septum four of 

 the original twelve ovules now begin to fail and shrivel, the 

 rest proceeding with their growth until about i'5 milHmetre 

 across, when three more fail, and ultimately only five become 

 mature seeds. On the other hand, with Vicia sativa nearly all 

 the twelve ovules give rise to mature seeds, only one as a rule 

 failing either in the early or later stage above described. I 

 may add that such a study should be made on moist green 

 pods in different stages, since the dry fruit could tell us but 

 little of the history of the ovules. 



Now this conspicuous difference in the history of the ovules 

 is associated with considerable contrast in the growth of the 

 pods, the pod of Vicia sativa, where nearly all the ovules form 

 mature seeds, becoming long and narrow, and that of Vicia 

 sepium, where many_ of the ovules fail, becoming short and 

 broad, so that the ripe fruits differ greatly in appearance. At 

 first sight one would be inclined to connect the shorter pod of 

 Vicia sepium with the greater failure of the ovules, since in 

 both species the original number of ovules is the same. But 

 on closer investigation we find that the contrast in length 

 cannot be so easily explained. In the first place, the ripe pod 

 of Vicia sepium is but partially filled by its seeds, whilst that of 

 V. sativa is nearly or completely filled. If the pod of the first 

 named had been quite full of seed, the argument would have 

 had some cogency ; but as it happens, large unfilled spaces occur 

 at the two ends of the seed-cavity due to the failure of the 

 ovules chiefly in those situations. We thus get an indication 

 of the independence of the size of the pod as far as concerns 

 the number of seeds. 



From this it would follow that the same dimensions of the 

 legume are in the main retained in the few-seeded and in the 

 many-seeded pods of Vicia sepium. Further inquiry indeed 

 shows that this is in a general sense the case, such differences 



