VITALITY AND GERMINATION OF SEEDS. 209 



alcohol fails to penetrate the seed coat or penetrates it 

 only with extreme slowness owing to the alcoholic mole- 

 cules being larger than the intermolecular interstices of 

 the external mucilaginous layer. In 50 p.c. alcohol on 

 the other hand, this layer swells up somewhat, though 

 not so much as in pure water. The enlargement of the 

 intermolecular interstices is however sufficient to allow of 

 the passage of the alcoholic molecules and the alcohol 

 which soon penetrates through the inner seed coat to the 

 embryo rapidly destroys its vitality. The greater deadli- 

 ness of 50 p.c. alcohol is therefore due to the fact that it 

 penetrates the integuments of the seed with much greater 

 readiness than does absolute alcohol. Once contact is 

 assured between the vital contents of the seed and the 

 alcohol the destruction of the vitality of the seed is as 

 certain with absolute as with 50 p.c. alcohol. 



After this preliminary observation a series of experi- 

 ments were made with a selected list of seeds. Every 

 experiment was checked by control experiments with 

 normal seeds and in most cases the comparative percentage 

 given is the mean of several similar experiments. The 

 seeds employed were Peas, Haricots, Hemp, Linseed, 

 Wheat and Barley, i.e., albuminous, starchy and oily 

 seeds, with hard and soft membranous coverings, with 

 hard and woody coverings and lastly with an external 

 mucilaginous coat in the case of Linseed. 



In addition to abs. alcohol and 50 p.c. alcohol, for 

 purposes of comparison the effect of water alone and of 

 an aqueous solution of mercuric chloride, on the seeds 

 was noted. The results of the experiments are drawn up 

 for the most part in tabular form, showing the effects of 

 different periods of immersion and also the longest period 

 of time that the seeds could withstand immersion, in the 



