VITALITY AND GEKMINATION OF SEEDS. 



227 



periods than they can withstand immersion in 50 p.c. 

 alcohol, or in absolute alcohol. 



The reason for this is that such a mixture contains a 

 sufficient percentage of alcohol to keep the seed dry, with 

 the molecular interstices of the integumentary coat un- 

 expanded and thus preventing the entrance of either water 

 or alcohol, whilst the amount of water which the mixture 

 contains is sufficient to prevent the drying action, which 

 absolute alcohol exerts by removing from the seed the last 

 traces of water which it contains, from coming into play. 

 The following table gives a comparison between the effects 

 upon Peas of absolute alcohol and alcohol containing a 

 little water. 



Peas. 



1 week. 



3 weeks. 



6 weeks. 



7 weeks. 



9 weeks. 



11 weeks. 



Absolute Alcohol. 



72 p.c germ. 



30 p.c. 



24 p.c. 



15 p.c. 



None. 



None. 



85—90 p.c. Alcohol. 



83 p.c. germ. 



58 p.c. 



42 p.c. 



40 p.c. 



31 p.c. 



18 p.c. 



At the 11th week, owing to the supply of Peas in alcohol 

 being exhausted, the experiment perforce ceased. It has 

 already been seen that the immersion of Peas in absolute 

 alcohol, owing either to the withdrawal of water or to the 

 actual penetration of the alcohol itself, causes a gradual 

 diminution of vitality and finally death. This diminution 

 of vitality seems to be accompanied, in the case of the 

 radicle, with a diminution of its geotropic irritability, for 

 in a few cases after immersion in absolute or 50 p.c. 

 alcohol, on germination the radicle may grow upwards 

 instead of at once bending downwards. If the seed be 

 near the surface of the ground the radicle may grow up 

 into the air and then soon withers. If the tip remains 

 underground it will finally curve downwards though it 

 describes a much wider arc than normally. The radicle 

 only grows upwards when it was pointing upwards to 



