THE DEHISCENCE OF FRUITS 



283 



is occupied by numerous aborted seeds, 3 to 5 millimetres long, 

 and varying from twenty or thirty to forty or fifty in number. 



This tremendous waste, not of ovules, but of seeds that could 

 find no room for further development, plainly indicates the 

 existence of a great tension within the living fruit. If the stony 

 walls by their pressure are able to prevent the proper growth of 

 all but a very few seeds, they are subjected in their turn to the 

 opposing strain of the expanding seeds ; and in the end the 

 seeds are successful in rupturing the walls, though too late for 

 the maturation of most of them. This is evidently what happens 

 on the tree, since it is the moist fruits that are found dehiscing. 

 The first stage in the dehiscence of Ravenala fruits is therefore 

 due to the expansive force of the growing seed, and drying does 

 the rest. One may note in passing that the genesis of the thick, 

 tough walls of this and other capsular fruits may lie in its being 

 a response to the expanding pressure of the growing seeds. 



That drying is a potent factor in the completion of the 

 process is shown in the behaviour of the " stones " of Ravenala 

 when allowed to dry after being removed from ripe, unopened 

 fruits. They begin to split loculicidally when they have lost 

 about 15 per cent, of their weight, but some also split septi- 

 cidally at the apex of the valves, the loculicidal dehiscence 

 ultimately prevailing. The loss of water during the drying in 

 air of the entire fruit may here be given, though the subject is 

 also dealt with in tables given in Chapters XII and XIV. 



Results of Drying in Air a Fresh Fruit of Ravenala 

 madagascariensis. 



The loss of weight of the stone without the seeds would be about 40 per cent. 



