SEED-NUMBER AND FRUIT-SIZE 341 



plant in the exceptional proportion of its pericarp ? In the 

 single-seeded fruits of Albizzia Lebbek the large size of the 

 pod in relation to the solitary seed is very conspicuous. But 

 those interested in the subject will call to mind other legu- 

 minous plants displaying fruits of the same character. Let 

 us take, for example, the pods of Cytisus Laburnum and of 

 Sophora tetraplera. Occasionally they contain only a single 

 seed ; and in such cases it will not be necessary either to 

 measure or to weigh them in order to perceive that, as 

 compared with the typical many -seeded fruits, the size of 

 the pod is quite disproportionate. However, if we rip open 

 one of these single-seeded legumes, and examine the interior 

 carefully, we make a discovery. There is, it is true, only 

 one seed, but we can discern with a lens the remains of 

 all or most of the missing ovules that existed in the ovary 

 before pollen was applied to the stigma. Here, then, is 

 the clue. 



But this opens up another subject for inquiry which is A problem 

 discussed with some detail in the next chapter, namely, the Si dUP 



abortion of ovules and the failure of fertilised ovules or questions re- 

 lating to the 

 of young seeds. Much depends in the history of the fruit abortion of 



on whether the original pollination of the stigma resulted the failure 



in the fertilisation of the ovules, or merely served to stimulate of seeds - 



the growth of the fruit. In the first event there would be 



produced a normally seeded fruit, but in the second event 



only a seedless one. It is, however, the partial failure of 



the ovules or seeds that will afford the most suggestive 



materials for study. If some of the ovules only are fertilised, 



important alterations in the form of the fruit may result ; but 



the character of the change in shape will be determined by 



the situation of the aborted ovules, whether at the extremities 



of the fruit, or in the midst of the other ovules. Changes 



in shape much less marked will occur, if the fertilised ovules 



or young seeds fail early in their development. If the seed 



fails at a later stage in its growth, but little effect is produced 



on the fruit. 



