CHAPTER VII 



HYGROSCOPICITY 



Hygroscopicity in a seed may be defined as the variation of Definition of 

 its water-contents in response to the changes in the hygrometric scScity. 

 state of the atmosphere, such a variation being due to its 

 property of readily imbibing moisture from the air and as readily 

 parting with it. This interesting quality, which is characteristic 

 of all vegetable substances and of much besides, has in recent 

 times been studied by numerous investigators, including 

 amongst others Jodin (1897), Berthelot (1903), Leo Errera 

 (1906), Becquerel (1907), and Demoussy (1907), the years in- 

 dicating the date of publication of the author's paper consulted. 

 The most comprehensive treatment of the subject is to be 

 found in the memoir of Leo Errera entitled " Sur I'Hygrosco- 

 picite comme cause de Faction physiologique a distance " 

 {Recueil de TInstitut Botanique Leo Errera^ Universite de Bruxelles^ 

 tome vi., 1906). Assisted by the previous researches of Classifica- 

 Warburg and Ihmori, he was able to direct attention to certain dXrent^ 

 principles involved and to show that hygroscopicity in its Errera'^ ^^° 

 widest sense has a far more extended significance than is 

 generally imagined, as is suflSciently brought out in his 

 classification of the various forms of this property, both 

 physical and chemical, which I have reproduced in Note 9 of 

 the Appendix. The matter as here dealt with appeals mainly 

 to the physicist and the chemist ; but it is essential, before 

 studying hygroscopicity as affecting plants, to bear in mind the 

 broad treatment of the subject which gives so much importance 



147 



