148 STUDIES IN SEEDS AND FRUITS 



to this paper. Hygroscopicity is there exhibited in the most 

 comprehensive sense, as displayed (a) in the condensation of 

 the water-vapour of the air on the cold surface of a glass ; 

 (^) in the capillarity of hair, wool, cotton, wood shavings, etc. ; 

 (<:) in the imbibition of water from the air by gelatine ; (d] in 

 the deliquescence of common salt ; (e) in the absorption of 

 water from the air by concentrated sulphuric acid ; and (/) 

 in the behaviour of quicklime. Becquerel, in applying this 

 classification to seeds, suggests two kinds of hygroscopicity : 



(1) physical, where condensation is affected by the cold, smooth 

 sides of the seed or by the walls of very fine capillary pores ; 



(2) chemical, when induced by the affinity of certain substances 

 for water (Annales des Sciences Naturelles Botanique, tome v., 1 907). 



Coming to the display of this quality by vegetable materials 

 in general, I will, before handling my own observations, take 

 my cue from the researches of Jodin on peas, and will then 

 look to the principle laid down by Berthelot for guidance in 

 the search after the significance of hygroscopicity in plant- 

 tissues. But it is necessary to preface my remarks by point- 

 ing out that the hygroscopic reaction understood by these 

 investigators, and always intended in these pages, is the 

 response of the permeable seed (by absorbing or yielding up 

 water-vapour) to the varying hygrometric condition of the air, 

 a never ceasing " give and take " process by which the 

 equilibrium between the seed and the air is maintained. 

 Theobserva- Jodin approached the subject from the biological and 

 Jodin'on Berthelot from the physical side, and both arrived at the same 

 peas. conclusion, that we are concerned with a quality that is inde- 



pendent of life. Jodin, in his paper published in the Annales 

 Agronomiques for October 1897, tells us that living and dead 

 peas (those recently grown and those that had long lost their 

 germinative capacity) exhibited much the same hygrometric 

 variation in the course of a year's exposure to ordinary air- 

 conditions. Stated as a percentage of the average weight of 

 the air-dry resting seed, his results give a variation for the live 

 peas of 8 to 23 per cent., and for the dead peas of n to 21 



