20 STUDIES IN SEEDS AND FRUITS 



its weight to 1012 grains by water-absorption. We thus 

 get the result : — 



Large, soft, pre- ^ . ^ Swollen seed on eve 



resting seed. i^esung iceu. of germination. 



1004 grains. 408 grains. 1012 grains, 



which expressed in ratios becomes : 



Shrinking ratio. Resting seed. Swelling ratio. 



2-46 I 2-48 



Modes of The ideal method of carrying out such observations would 



fheshriXifg naturally be, as was done in the instance just given, to note 

 ^d swelling the shrinkage and swelling of a single seed, that is, to take its 

 maximum weight in the green fruit, to weigh it again after 

 prolonged air-drying, and to weigh it once more when on the 

 eve of germination. This involves the separation of the pre- 

 resting seed from the parent plant ; and although one can 

 choose the time when the cord or funicle is beginning to 

 shrivel and the vital connections are being severed, still it is 

 open to the objection that a seed thus detached does not dry 

 under normal conditions. However, checks can often be 

 found by comparing the state of the coats of a resting seed 

 thus produced with that of a typical resting seed ; whilst any 

 marked divergence from the average can be detected by a 

 comparison of the swelling ratios of the two seeds. With 

 seeds typically impermeable, a resting seed thus artificially 

 obtained often lacks the impermeability of the outer coverings ; 

 and its shrinkage, as indicated by the change in weight, is not 

 so great as with the seed that has properly contracted on the 

 plant. 



On the other hand, typical perineable seeds when dried 

 under these conditions frequently shrink too much. Never- 

 theless, normal results were at times obtained, some of which 

 are mentioned below ; whilst the behaviour of the imperfectly 

 shrunken seeds has ofFered a fruitful field of investigation. 



But there is another plan, and that is by comparing the 

 average shrinkage of a number of detached pre-resting seeds 

 with the average swelling of a number of resting seeds prepar- 



