FATE OF SEEDS INDICATED BY BALANCE 231 



impermeable seed when its coats are broken. Being normally 

 in a state of partial desiccation, it at once begins to supply 

 the deficiency by absorbing moisture from the air. From 

 inorganic substances like glass, we should look for no such 

 behaviour. They have little or no water to lose under 

 desiccating conditions, and in consequence have little or no 

 water to regain. This matter is discussed in Chapters VII. 

 and VIII. It will be there seen that Berthelot lays stress on 

 the contrast in behaviour between inorganic substances (like 

 porcelain and metals) and plant-tissues, the first drying com- 

 pletely in air, whilst the second do not. 



There is nothing to lead us to expect that the kernels 

 of seeds of any type would ever lose their capacity for 

 behaving hygroscopically and become non-hygroscopic, inert 

 substances like porcelain and metals. If this were the case, 

 Berthelot's principle of reversibility would lose much of its 

 significance. It must, however, be admitted that the semi- 

 stony consistence of the kernels of some old permeable seeds 

 would at first sight seem to justify such a belief. At one time 

 I thought that the seeds of Msculus Hippocastanum (Horse- 

 chestnut) and of the Acorn {Quercus Robur) would in time 

 assume some of the characters and behaviour of inorganic 

 material, such as chlorite and opal, as regards the diminished 

 water-contents and the small hygroscopic reaction ; but this 

 proved to be incorrect. As regards hygroscopicity, reference 

 has already been made to the effect of time on the behaviour 

 of the seeds of the Horse-chestnut in their coats, the results 

 of the experiments being tabulated in Chapter VII. We 

 saw there that, whether six months or thirty months old, the 

 hygroscopic reaction was much about the same, namely, 2*o to 

 2*4 per cent. Whilst writing these remarks I have conducted 

 another experiment on the same seeds three or four years 

 old ; but in this case the seeds were first bared of their 

 coverings. The three-year-old seeds give a hygroscopic range 

 of 2-4 per cent., and the four-year-old seeds of 3*5 per cent. 

 So also with reference to the bared seeds of the Acorn. I find 



