58 



Scientific Proceedings^ Royal Dublin Society. 



Buoyancy of Fleshy Fruits — continued. 



It will be seen that while the majority of these fleshy fruits sink at once, 

 their buoyancy is usually increased, sometimes very largely, by drying. 

 Taking the seventeen plants in which the buoyancy of both fresh and dried 

 fruit was observed, we find that the result of drying is to increase the 

 buoyancy from an average of 2'3 days to an average of 12"9 days. While the 

 fresh fruit of only four of these seventeen plants was buoyant, the dried fruit 

 of all but five of them floated for some time. In the case of Berberis vulgaris 

 and of Khamnus Frangula, the effect of drying was to diminish the buoyancy. 



When dried fruits, such as rose-hips, are placed in fresh water, and air is 

 not excluded, fermentation often sets in, and the fruit, either before or after 

 sinking, becomes inflated with gases, and floats buoyantly until disintegration 

 sets in ; what the result of this is on the vitality of the seeds was not tested. 



The seeds of a large majority have no buoyancy, even when dried. All 

 but twelve out of the thirty-six sank at once, and of these twelve only Ilex 

 Aquifolium, Cornus suecica, and Empetrum nigrum floated for a week or ten 



Vaeiability of Buoyancy in Seeds of the same Species. 



In any batch of seed — even in a group of seeds taken from the same seed- 

 vessel — a considerable variation in buoyancy exists. In the case of those that 

 sink at once, the lightest seeds will take twice, or three times, or even four 

 times as long to reach the bottom as the heaviest seeds will. Similarly, in 

 those which float, the most buoyant seeds will sometimes float up to four 

 times as long as the least buoyant. On the whole, to obtain the average 



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