HYGROSCOPICITY 



The feature in this table which will prove 

 the greatest significance to us, in respect to the 

 of impermeable seeds when exposed to the air, is 

 which shows that the water regained from the air, 



151 



to be of 



behaviour 



that 



after 



fresh plant-tissues have been exposed to a temperature 

 of 100° to 110° C, is the water of the dead plant and of 

 the plant dried in the air, and is therefore independent of 

 vitality. 



In the above table I have pieced together the indications 

 of different experiments in order to emphasise certain points 

 in the behaviour of plants when exposed to natural and artificial 

 desiccation. After reading Berthelot's paper I experimented 

 on some fresh leaves of the Hazel {Corylus Avellana)^ with the 

 results below given. His principle is well illustrated there, 

 and we can see at a glance that the water which the fresh leaves 

 gained back from the air after being exposed to a temperature 

 of 105° C. is the water which they would have contained as 

 ordinary air-dried leaves. For about three years I have been 



The testi- 

 mony of 

 Hazel 

 leaves. 



Experiments by the Author on fresh Hazel (Corylus Avellana) 

 Leaves in illustration of Berthelot's " Principle of 

 Reversibility." 



Hundred-grain samples of the fresh material were used. In the case of experiments 

 A and B, the sample was first dried in air for about five days, when it reached a stable 

 weight. It was then subjected to a temperature of 105° C. for ih hours, and afterwards 

 left exposed to the air of the room for three or four days, when it ceased to gain weight. 

 In the case of experiments C and D the fresh materials were placed in the oven without 

 previous drying in air. 



