PERMEABILITY AND CLASSIFICATION iii 



ments is the Index of perfect maturation, he proceeded to study 

 the question of permeability from that standpoint. Taking 

 only " germinable " seeds, he finally inferred that the greener 

 seeds are the less mature and the more impermeable. The 

 general trend of my observations is all against such a view, 

 deficient shrinkage and loss of impermeability being uniformly 

 associated. The green colour of imperfectly shrunken seeds, 

 where the normal resting seed was impermeable, often came 

 under my notice ; but always connected with loss of im- 

 permeability more or less complete. 



Taking the seeds of Acacia Farnesiana^ the shrinking process 

 of which I observed in Grenada and Jamaica, I found that 

 full-sized so-called unripe seeds, when allowed to go through 

 the shrinking stage detached from the pod, remained green, 

 though in other respects resembling the normal brown resting 

 seed. I did not test their permeability, but since 85 per cent. 

 of the brown seeds from the same plants proved to be im- 

 permeable, the margin of possible advantage left for the green 

 seeds was small. Dr Gola's results have proved of so much 

 service to me that one feels loth to dissent from him when he 

 associates impermeability with immaturity ; but I feel confident 

 that should he ever extend his researches to the shrinking 

 process of seeds, he will arrive at a different conclusion. 



This chapter may be concluded with the remark that there 

 are several points in the behaviour of seeds, notably those 

 concerned with the differences in the water-contents of perme- 

 able and impermeable seeds, and with their absorptive capacities 

 after the oven test, which will be further elucidated in the 

 succeeding chapters, especially in that dealing with Hygro- 

 scopicity. 



SUMMARY 



(i) According to the existence or absence of impermeable cover- 

 ings, seeds are here divided into three groups : [a) impermeable, where 

 all the normal seeds are impermeable to w^ater ; (/;) permeable, vv^here 

 all the seeds are permeable ; and {c) variable, an extensive group 



