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176 STUDIES IN SEEDS AND FRUITS 



that the dry open pods of Gullandma bonducella and C<esalpinia 

 Sappan, as they lay on the table in my room in Grenada, used 

 to vary in their weight as much as i or 2 per cent, from day 

 to day, especially between the evening and the following 

 morning. 



In concluding this chapter we may observe that the question 

 we put to ourselves a few pages ago as to the extreme limit of 

 a seed's hygroscopicity is very far from being answered, and 

 perhaps it may prove to be not altogether pertinent to the 

 subject we are discussing. With the data at our disposal it 

 seems unnecessary to follow up this special point any further 

 at present ; and indeed it will appear from the subsequent 

 chapters that a number of queries claim a reply first. 



SUMMARY 



(1) Hygroscopicity in a seed is defined as the variation of its water- 

 contents in response to the changes in the hygrometric state of the 

 atmosphere (p. 147). 



(2) After referring to the important memoir on the subject of 

 hygroscopicity in general by Leo Errera and to the display of this 

 quality by vegetable materials in particular, special attention is directed 

 to the researches of Jodin and Berthelot. Whilst the first-named 

 investigator approached the subject from the biological and the second 

 from the physical side, both arrived at the same conclusion : that we 

 are here concerned with a quality that is independent of vitality 

 (p. 148). 



(3) Jodin, experimenting on living and dead peas, found that they 

 exhibited much the same hygroscopic variation in the course of a year's 

 exposure to ordinary air-conditions (p. 148). 



(4) Berthelot, experimenting on different vegetable materials (leaves 

 and stems of grasses, etc.), shows that the peculiar property possessed by 

 air-dried vegetable substances and some other materials of regaining 

 from the air the water which they yield up when exposed to a 

 temperature of 100 to 1 10 C. is a function of the hygrometric state of 

 the atmosphere and is essentially a physico-chemical process independent 

 of life. We will take as illustrating this principle 100 grammes of 

 fresh plant-substance which is reduced to 50 grammes by air-drying in 

 an ordinary room. Exposing it then to a temperature of 1 00 to 1 1 o C., 

 its weight is further reduced to 40 grammes ; but on being allowed to 



