28 OUR WOODLAND TREES. 
a partial reply by a reference to a few known and 
isolated facts. These lead us to the conclusion 
that the vitality of seeds is extremely variable— 
in some cases being of short duration, in others 
extending over marvellous periods of time, when 
circumstances have prevented the operation of the 
process of germination. Instances of seeds which 
have germinated after having lain dormant for 
more than a century have been authenticated, and 
there is presumptive evidence of the germination 
of seeds which have been disentangled from 
geologic strata. Even if we alone accept the re- 
corded instances of germination suspended over 
the long period of a hundred years, can we do 
otherwise than marvel at the persistent vitality 
thus displayed ? 
