5C STUDIES IN SEEDS AND FRUITS 



associated with the loss of impermeability, and that these results 

 are primarily due to the deficient shrinkage of the pre-resting 

 seed. In my experiments other impermeable seeds behaved 

 like those of Guilandina honducella. When they had lost their 

 impervious character they swelled less and in consequence 

 required less water for germination. The loss of imper- 

 meability was in fact associated with marked diminution in the 

 swelling ratios. A good example of this result was afforded 

 in the case of the seeds of Dioclea reflexa, gathered by me in the 

 woods of the Grand Etang in Grenada, their mode of occur- 

 rence being described in Chapter V. Here the origin of the loss 

 of impermeability could be readily traced, and the permeable 

 seeds were easily recognised by their larger size, darker hue, 

 softer coverings, and by other indications of deficient shrinkage. 

 The outcome of a number of observations was as follows : — 



The permeable seeds of Dioclea reflexa in swelling for germi- 

 nation increase their weight by about 80 per cent ; whilst the 

 impermeable seeds just double their weight. This difference 

 is not so great as in other impermeable seeds, since the seed- 

 coverings act somewhat irregularly, as described in Chapter IX. 



If the share taken by the coats in the swelling process is 

 eliminated, the contrast between the swelling capacities of 

 these two types of seeds is made more evident, the kernel of 

 the permeable seed showing an increase of weight of about 

 80 per cent., and that of the impermeable seed of about 130 

 per cent. The swelling mechanism of these seeds is discussed 

 in Chapter IX. 



The behaviour of the seeds of Guilandina honducella and 

 Dioclea reflexa must be typical of many other leguminous seeds 

 with impervious coats. Any influence that impedes the 

 shrinking of the soft seed of the green pod tends to prevent 

 the acquirement of impermeability. One may cite in this 

 connection the seeds of Casalpinia sepiaria and Casalpinia 

 Sappany which are often impermeable when allowed to ripen 

 on the plant, but permeable if they have been prematurely 

 detached from the pod, as described in Chapter V. 



