ADDITIONAL EVIDENCE 133 



exposed to a temperature of 100 C. in the broken or divided 

 condition. In five days they regain most of the weight lost, 

 and in a week or two they would regain all, maintaining their 

 original weight subject to ordinary hygroscopic variation. 



When comparing the absorptive capacities of permeable Theabsorp- 

 and impermeable seeds it is requisite that the drying and dtfes of*' 

 shrinking process should be complete. In all these experi- th^dnSg 

 ments only seeds were employed that had accomplished the process has 



not been 



drying process and had attained a stable weight. If we place completed. 



in the oven a seed that has not yet begun to dry, or has not 



yet completed that process, we meet with a very different 



behaviour. A bared fresh Horse-chestnut seed (Msculus) 



cut up in slices, that had had its weight reduced in the oven 



from 100 to 52 grains, increased its weight by only 7 grains 



(52 + 7) during eight days. In the same way the seed of a 



fresh Acorn (Quercus Robur\ after its weight had been reduced 



in the oven from 100 to 58 grains, added only 4 grains to its 



weight during an exposure to the air of eight days. A broken 



seed of Dioc/ea reflexa which had not completed the drying 



process lost 20 per cent, of its weight in the oven, and after 



five days was still 5 per cent, short of its original weight. 



On the other hand, normal resting seeds of the same plant, 



which lost 8 '6 per cent, of their weight in the oven, behaved 



like typical impermeable seeds during an exposure of five days 



to the air, increasing their original weight by 9 per cent. 



On the behaviour of seeds exposed to a temperature of 

 1 00 C. before they have commenced or before they have 

 completed the drying process, the principle of Berthelot, 

 discussed at length in Chapter VII, throws a flood of light. 

 The water which they subsequently regain from the air is 

 merely the water of hygroscopicity, which they would hold 

 whether living or dead. This amounts on the average to 

 only about 5 per cent, of the weight of the moist fresh seed 

 that has not begun to dry. Most seeds lose quite 50 per 

 cent, of their weight in the normal drying process, so that 

 there would be a large proportion of the water which a fresh 



