HYGROSCOPICITY 155 



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

 permeable and impermeable seeds, it is evident that an seed?^both 

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



. , 1 . , 3 . , . . . and imper- 



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

 contains only the water of hygroscopicity, and that the wate°"of 

 water of vitality disappeared in the drying process. It g^^T'it 

 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 fngleedr^" 

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



Ml -1 f 1 f • 1- --r-i • • , water associ- 



still contained some 01 the water or vitality. 1 his residuum ated with 

 of the water of vitality left in the deficiently air-dried function, 

 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 



