THE ABORTION OF OVULES 25 5 



millimetres. We can thus perceive, as explained with regard 

 to Albizzia pods, why no effect is produced on the form of the 

 fruit by the failure of one of the seeds. Had the ovule failed 

 in an early stage the effect might have been noticeable. But 

 even then, as in the case of Ulex pods, it is probable that there 

 would have been no constriction in the pod's width, a result 

 due to the structure of the pod itself. 



Capsular fruits now claim our attention ; and it may be The failure 

 said of them, as of the legumes, that the mature seeds, the capsules, 

 young seeds that fail before they attain any size, and the 

 ovules that abort early, make up the full complement of the 

 ovules in the flower. This is well brought out in the average 

 results given in the table preceding the summary of this 

 chapter, and one need scarcely labour the point here. They ' 

 all behave, for instance, like the fruits of Arenaria peploides. 

 The primal complement of twelve ovules in this case can 

 almost always be recognised in the fruit, whether the fruit only 

 contains five or six seeds or as many as ten, the failures making 

 up the balance. All the ovules of the unfertilised ovary can 

 be thus accounted for. They are potentially seeds from the 

 beginning. The occurrence of rudiments of ovules in the 

 flower raises quite another question, which will be dealt with in 

 a later page. 



As an example of the influence of the failure of ovules on illustrated 

 the form of capsules, I will first take that of Iris Pseudacorus. iJg Pseuda- 

 Here there are two rows of ovules in each of the three com- «=°''"s- 

 partments of the fruit ; and they all begin to enlarge after the 

 fertilisation of the ovary. If most of the ovules in each of the 

 two rows mature as seeds, the seeds are closely packed and 

 overlap each other and are irregularly wedge-shaped ; but if 

 the ovules in only one of the rows become seeds, whilst those 

 of the other row fail, then the seeds assume a disc-like form. 



Failure of some of the ovules is, however, a normal event, 

 and much depends on their number and on their situation. 

 Thus the average result given in the table at the end of the 



