THE IMPERMEABILITY OF SEEDS 65 



There are, however, one or two points to which further 

 reference might be made. Thus, to take the first query, it 

 may be replied that even in the case of the most impermeable 

 seeds the effect of being kept in the dry air of a room for 

 many years would be undoubtedly to favour the development 

 of small cracks in the outer covering, thus converting them by 

 degrees into permeable seeds. My observations on the seeds 

 of Entada scandens (Chapter X) will go to show how this could 

 be brought about. We can thus perceive how much less 

 likely it is that impermeable seeds exposed without protection 

 to the weather could withstand year after year the alternating 

 conditions of heat and cold, of sun and shade, of drought and 

 humidity, which in one form or another they would experience 

 whatever their situation. In an elaborate series of experiments, 

 in which he reproduced the extreme changes between moist and 

 dry conditions and between heat and cold in various shapes, 

 such as an ordinary climate would present, Dr Gola found that 

 the seeds lost their impermeability. To come to a matter of 

 my own observation, it is doubtful whether any of the 

 numerous impermeable seeds washed up on tropical beaches 

 could withstand for many years exposure to the sun and rain. 

 All of them would show sooner or later signs of wear and tear 

 in the injuries to the outer coats. 



On the other hand, buried in the soil, the seed would be 

 more or less safeguarded against the risks to which a seed 

 lying on the ground would be exposed. But the degree of 

 protection would vary with the depth below the surface, so 

 that the seed deepest down, as shown by Duvel, Crocker, and 

 Ewart, would have the longer life. At the same time new 

 dangers might arise ; but on the whole it seems likely that 

 under such favouring conditions as characterise the typical 

 Australian forests, the buried seed might retain its imper- 

 meability for much longer periods than when kept dry in 

 cupboards or in botanical museums. 



But this raises again the second question whether the 

 germinative capacity would be similarly retained. Of this it 



5 



