68 STUDIES IN SEEDS AND FRUITS 



seeds all possess more or less impermeable coats, and three-fourths are 

 leguminous (p. 62). 



(5) It is suggested in this chapter that seed-longevity should be 

 regarded as determined by two factors, represented in the imper- 

 meability of the coats and in the persistence of the protoplasmic 

 constitution of the embryo-kernel (p. 63). 



(6) It is also suggested that, accepting impermeability as an adaptation 

 to soil-conditions, we should leave to the future investigator these two 

 points to determine : [a) whether the impermeable seed would retain its 

 germinative capacity longer in the soil than in the air ; [b) as to the 

 relative durability of the impermeability of the seed-coats and the 

 germinative capacity (p. 64). 



(7) Recent investigators lay stress on the fact that negative results 

 obtained by earlier investigators in testing the persistence of the 

 germinative powers of hard seeds were more probably due to their 

 inacquaintance with the right methods of procuring germination than 

 to failure on the part of the seeds (p. 66). 



(8) Whilst considering that a combination of the theories of Crocker 

 and Ewart would present the best working hypothesis, the author is 

 inclined to the view that the most practical tests of the potential 

 vitality of an impermeable seed are to be found in the constancy of its 

 weight under all ordinary conditions and in the lapse of years. He 

 would presume the germinative capacity of such a seed, whatever its 

 antiquity, provided, as has just been implied, that its coats are sound, 

 that it absorbs no water, and that it makes no response by alterations 

 in its weight to the varying hygrometric states of the air. The author 

 also does not regard it as prudent to ignore altogether the accumulation 

 of evidence respecting the great age of "germinable" seeds found in 

 ancient graves or when an old soil is disturbed (p. 66). 



(9) Lastly, the opinion of Nobbe and of later investigators that the 

 seat of impermeability lies in the outer coverings of the seed has been 

 confirmed by the results of the recent researches of Miss J. White, 

 who places it in the case of small seeds in the cuticle and with large 

 seeds often in the outer palisade cells (p. 66). 



