VITALITY AND GERMINATION OF SEEDS. 



225 



the seed is dry and even if the integument or outer 

 layers of the seed contained a trace of water it would be 

 withdrawn by the alcohol leaving them perfectly dry, it 

 follows that the only medium by means of which the 

 dissolved salt can be carried into the substance of the 

 seed is the absolute alcohol. The penetration of the 

 mercuric chloride is therefore a measure of the penetration 

 of the absolute alcohol. 



Peas. 



1 day. 



3 days. 



5 days. 



3 weeks. 



6 weeks. 



7 weeks. 



9 weeks. 



HgCl2 Alcoholic 

 Solution. 



82 p.c. 



32 p.c. 



16 p.c. 



6 p.c. 



None. 







Absolute Alcohol. 



95 p.c. 



89 p.c. 



80 p.c. 



28 p.c. 



20 p.c. 



16 p.c. 



None. 



An examination of the percentages given in this table 

 shows clearly that the alcohol even after it has penetrated 

 the integument of the seed and reached the embryo is not 

 immediately fatal. The dormant protoplasm of the seed 

 is not killed by the first traces of alcohol which reach it 

 but resists the action of the alcohol for a short time if the 

 amount which has penetrated is but small in quantity. 

 If, however, the alcohol contains dissolved mercuric 

 chloride the rapidity of its fatal action is much accelerated, 

 though even here the amount of the salt which penetrates 

 must reach a certain degree of concentration before vitality 

 is destroyed. Thus after 21 days immersion in the alco- 

 holic solution on testing with ammonium sulphide, the 

 salt had penetrated at least as far as the outer part of the 

 radicle, which became slightly blackened shewing the 

 presence of the mercury salt. Yet of such seeds 6 per 

 cent, were still capable of germination. The majority of 

 the seeds on examination shewed the embryos to be 

 permeated by the poisonous salt and such seeds were of 

 course incapable of germination. In several cases after 

 so little as three or four days immersion the outer side of 



