GERMINA TION 



137 



iiitorc-luin<,^o of substance, due to vital action, hetweeu the seed and the 

 surrounding atmosphere, altliough c\treniel\' shght, so long as the former 

 possesses its vitality. 



The evidence as to h-ngtii of time (hiring wliich seeds can retain their 

 vitaHty is extremely contradictory, and the greatest diversity of oj)inion 

 exists concerning this point. Our best authorities bclicxc that we have 

 no conclusive e\'idciic(> that the period is longer than about fifty years, 

 although, u])on the other hand, we have no positive evidence that it is 

 not ver\' nuich Jouiicr. 



Germination. — ('oiidifions of (IcnnliKifioii.- (u-rniination dciiends 

 u])on (Da specific temperature, varying for seeds of dillerent species 

 and for those of the same species when they hav(> become" habituated 



