HYGROSCOPICITY 155 



In the first place, as regards the contrast between (a) That air- 

 permeable and impermeable seeds, it is evident that an s^ds^^^a 

 air-dry permeable resting seed, which has assumed a stable pe«neable 

 weight, subject only to ordinary hygroscopic variations, meable, con- 

 contains only the water of hygroscopicity, and that the watero? 

 water of vitality disappeared in the drying process. It sJMkity 

 also becomes apparent that the impermeable seed con- 

 tains only the water of hygroscopicity, but in a diminished 

 amount, so that when deprived of the protection of its 

 impermeable coverings it at once begins to supply the deficit 

 by abstracting moisture from the air until a stable weight is 

 reached. 



The implication of course is that resting seeds completely 



air-dried, whether permeable or impermeable, possess only 



the water which is independent of vitality. If Berthelot's 



principle is true and the implication is valid, there is in the 



typical resting seed no water that is associated with any vital 



function. (I am not here speaking of water locked up in 



chemical combination in the seed's tissues, since that may be a 



property of both living and dead matter.) Should the seed 



exposed to a temperature of 100° C. in the oven yield up (6) that in 



more water than it subsequently regains from the air, the ^g s^ds^ " 



inference is that it had not completed its drying in air and there is no 



i- . ,. <-i->i ■ ■ 1 waterassoci- 



still contained some of the water of vitality. This residuum ated with 



of the water of vitality left in the deficiently air-dried Unction. 



seed has nothing to do with the life of a resting seed, 



but merely represents the remains of the water of the 



large, soft pre-resting seed of the moist green fruit, a seed 



that would have proceeded with its growth and with its 



development into a young plant without any pause, if the 



resting period had not been imposed on it through external 



influences. The resting seed needs no water to prolong its 



life, the presence of water being more likely to curtail its 



existence than to endow it with longevity. Indeed, there 



would seem to be more than fancy in the speculation of 



M. Demoussy that a perfectly dry seed kept protected from 



