144 STUDIES IN SEEDS AND FRUITS 



the water-contents are lost in the oven ; whilst the seed's 

 attempt to regain from the air the water lost is retarded, but 

 not prevented, the original weight being in time attained. 

 The retardation in the process of re-absorption is, however, 

 very marked, since in the Broad Bean and Scarlet-runner the 

 period is extended from two to six weeks and in the Pea from 

 one to two weeks. 



There are several points raised in the foregoing remarks 

 which will be elucidated in the chapter on Hygroscopicity, 

 notably, that concerned with the return of permeable seeds to 

 their original weight after being heated. Only completely air- 

 dry seeds would thus behave, since seeds that are still drying 

 would fall considerably short of the weight they possessed 

 before being placed in the oven. 



SUMMARY 



(i) This chapter contains the bulk of the data on which are 

 based the distinctions in behaviour between permeable and impermeable 

 seeds, which are described and illustrated by typical examples in 

 Chapter IV. 



(2) The capacity of increasing their weight considerably by absorb- 

 ing moisture from the air, when impermeable seeds are deprived of 

 the protection of their coats, is confirmed by the results of ex- 

 periments on the seeds of other plants. Other results also go to 

 confirm the conclusion drawn for type seeds in Chapter IV, that the 

 gain in weight is far more rapid when the kernel is completely bared 

 than when the coats are merely punctured. The average results of all 

 experiments on this absorptive capacity of impermeable seeds are 

 tabulated ; and it is generally concluded that leguminous seeds of this 

 type when deprived of the protection of their coverings as a rule 

 increase their weight between 5 and 10 per cent, in a few days 



(3) The indications, though limited, go to show that impermeable 

 seeds retain their ultra-dryness for a number of years (p. 119). 



(4) The data show that the capacity of absorbing water from the 

 air when an impermeable seed is bared of its coats is greater in the 

 tropics than in temperate climates, and that the gain in weight is 

 maintained longer when it is acquired slowly, as in filed seeds, than it 

 is when acquired rapidly, as in bared kernels (p. 120). 



