138 STUDIES IN SEEDS AND :FRUITS 



We have seen that the ultra-dryness of the kernel of an 



impermeable seed is maintained through the impervious 



character of its coats. In further illustration of the great 



The resist- resistance which the seed is able to oiFer on account of its 



byimperme- impermeable coverings to the injurious influence of external 



hiehtempe*" Conditions, I will discuss the results of some experiments 



atures. illustrating their behaviour under high temperatures. Although 



none of the seeds germinated after exposure to a temperature 



of 1 00° C., their behaviour under the test was very instructive ; 



and it would seem that in no better way can the contrast 



between permeable and impermeable seeds be shown than in 



their modes of responding to different stages of heat. 



It is of course natural that a seed-covering which is neither 

 As ex- hygroscopic nor pervious should have this influence. Yet 



Batada ^ some very curious effects are produced when impermeable 

 &S?andhia'^ seeds, such as those of Entada scandens and of Guilandina 

 bonducella. bonducella, are exposed in an oven to a temperature of 100° to 

 110° C. They are well brought out in the accompanying 

 table, which contains the results of two simultaneous experi- 

 ments on these seeds ; and in order to emphasise the peculiarity 

 in the behaviour of the impermeable seed when heated with its 

 coats intact, I have added the results for the same seed when 

 subjected to a similar high temperature in the broken condition.- 

 It is shown in the columns of this table that in their coats 

 these seeds behaved in a very similar fashion after an exposure 

 for two hours to a temperature of 100° to 110° C. They lost 

 respectively 2-7 and-i*9 per cent, of their weight, the subsequent 

 efforts of both to supply the loss by absorbing water from the 

 air having a very slight result. Both of them then doggedly 

 resumed in their altered condition their previous im- 

 permeability, making no hygroscopic response to the variations 

 in atmospheric humidity and gaining back no weight on being 

 immersed in water. If we contrast this with their behaviour 

 when deprived of the protection of their coats (as indicated by 

 the average results of several experiments on other seeds of 

 the same species), we find that in the oven test they lost 



