ON TIMBER TREES 
the existing trees have passed and through which 
the diversified hereditary factors were implanted 
in their racial germ plasms. 
A knowledge of this story we owe to the geolog- 
ical botanists. They have sought diligently in the 
rocks for fossil remains, and by joint effort, search- 
ing all around the world, have been able to repro- 
duce a picture of the main story of the evolution 
of existing forms of vegetable life. 
It is by recalling the story which they tell us, 
and thus alone, that we are enabled somewhat 
clearly to apprehend the possibilities of variation, 
and through variation of so-called new develop- 
ment—consisting essentially of the re-combination 
and intensification of old ancestral traits—that we 
have witnessed in the case of many tribes of plants 
in the course of our experiments. 
A brief resume of this story of plant life in the 
past, with particular reference to our own flora, 
will serve in the present connection to explain why 
there is every warrant for believing that each and 
every one of our forest trees contains submerged in 
its heredity the potentialities of a development of 
which its exterior appearance gives but faint 
suggestion. 
It appears that there is full warrant for the 
belief that the modern flora originated in the 
northern hemisphere, and probably in the region 
[181] 
