-I yo STUDIES IN SEEDS AND FRUITS 



under i per cent. Ordinary cotton-wool, it may be added, 

 exhibited under my tests a hygroscopic variation of only 2 per 

 cent., which is merely what one would look for in hairless 

 permeable seeds. 



Hygro- We may infer from Berthelot's principle that hygroscopicity, 



germination, being associated with the water which the seed, living or dead, 

 holds in maintaining its equilibrium with the air, has nothing 

 to do with germination. It has, however, often the appearance 

 of bringing about germination. One may gather fresh acorns, 

 separating at a touch from the cupule on the tree, and leave 

 them exposed in a saucer in an ordinary room for two or 

 three weeks, and some of them will germinate. One may 

 stand a dry, open test tube half filled with seeds of Abrus 

 precatorius in water in a tall glass vessel which is subsequently 

 covered over, and in the course of a week or two a few of 

 them will be found in a germinating or at least in a swollen 

 condition. But in neither case has this anything to do with 

 the water of hygroscopicity. 



In the case of the acorns, as shown in a later chapter, they 

 still contain, on falling out of the cupule, a large excess of 

 water, and it is this excess that is utilised in the early 

 germination. In this freshly detached state the embryo of the 

 future oak as it lies enclosed in the shell is almost in the act 

 of germination, and indeed is apt to germinate in spite of its 

 drying condition. As they lie drying on the table the chances 

 are fairly balanced whether the acorns will germinate before 

 the loss of water renders that impossible, or whether the 

 process of drying will proceed so fast that the germinative 

 capacity is unable to assert itself. 



In the case of Abrus precatorius y should the vessel be 

 exposed to the usual diurnal changes of temperature, con- 

 densation of the water-vapour in the heavily charged air would 

 probably occur and liquid water would be likely to come 

 in contact with the seeds, thus introducing another order 

 of phenomena. Nobbe (pp. 105-108) lays stress on the 

 point that contact with liquid water is essential for inducing 



