PERMEABLE AND IMPERMEABLE SEEDS 77 



In the first place, the only impervious portion of the seed- 

 shell is the outer skin and the hardened tissue immediately 

 beneath it, but little effect being produced by merely filing the 

 cuticle. . If we file through this outer impervious portion, it 

 makes but little difference in the subsequent behaviour of the 

 seed whether we expose the kernel or file only half through 

 the shell. 



In the next place, it should be noted that whilst the 

 freshly bared seed gains its maximum weight by Imbib- 

 ing moisture from the air in a few days, the filed seeds 

 occupy some months in reaching their greatest weight. 

 They then remain at about the same average weight and 

 behave like permeable sepds in their response to the hygro- 

 metric variations of the atmosphere. But the most note- 

 worthy feature in the behaviour of these filed seeds is that 

 they retain their germinative capacity iafter two years in 

 this condition. 



In the third place, the behaviour of the filed impermeable 

 seeds of Guilandina honducella may be contrasted with that 

 of the permeable seeds of Canavalia ensiformis, where, as 

 before described, the effect of puncturing the seed-covpr- 

 ings is merely to increase to some degree the hygroscopic 

 variation. 



Such, then, is the contrast in the behaviour between 

 permeable and impermeable seeds as described in the case 

 of two type seeds in the previous pages. The principal 

 differences are there outlined to a sufficient extent for this 

 introductory notice of my observations on this subject. 

 But there still remain some interesting features in the 

 absorptive capacity of impermeable seeds to be noticed and 

 some general reflections to be made before this chapter is 

 brought to a close. 



An accident led me to the discovery of another singular 

 quality of impermeable seeds, one that probably could have 

 been foreseen, had the successive stages of this inquiry followed 

 the order adopted in this chapter. However, it was this 



