66 



STUDIES IN SEEDS AND FRUITS 



The little 

 value of 

 negative 

 evidence. 



The seat of 

 impermea- 

 bility. 



may be said that we shall probably be never quite secure in our 

 interpretation of Nature's experiments in this direction. But 

 this insecurity does not invalidate the testimony altogether ; 

 and it scarcely seems prudent to ignore altogether the accumu- 

 lation of evidence respecting the high antiquity of "germinable " 

 seeds found in ancient graves or when an old soil is disturbed. 



With regard to the little value of negative evidence in 

 such an inquiry, I point out in the next chapter that we can 

 never be certain that the failure is due to the incapacity of 

 the germinative powers and not to the method employed. 

 Both Crocker and Ewart are emphatic on the point that it 

 would require more evidence than was deemed necessary by 

 the earlier investigators to convince us that the cause of the 

 failure to respond by germination to the call of their experi- 

 ments lay always with the seeds. I venture to think, and 

 here I am supported by a considerable amount of evidence 

 given in the succeeding chapters, that the truest test of the 

 potential vitality of an impermeable seed is to be found in 

 the constancy of its weight under all ordinary conditions and 

 under the influence of time. If a seed with sound coats 

 gained nothing in weight after weeks of immersion in water, 

 made no response to the varying hygrometric changes of the 

 atmosphere, and preserved the same weight for a number of 

 years, I would presume its germinative soundness, whatever its 

 previous history or whatever its attested antiquity. 



Not the least important part of Professor Ewart's memoir 

 is the account given by Miss White in an appendix of the 

 results of her investigation of the structure of coats of imper- 

 meable seeds. After making a microscopical examination of 

 the coats of nearly seventy species of impermeable seeds which 

 had been the subject of Professor Ewart's inquiry, she formed 

 the following conclusion : " As a general rule in small and 

 medium-sized seeds the cuticle is well developed, and repre- 

 sents the impermeable part of the seed-coat ; whilst in the case 

 of large seeds, such as those of Adamonia Gregorii, Mucuna 

 gigantea^ Wistaria Maideniana^ and Guilandina bonducella^ the 



