47 
thousand years ago, long after the precession theory would have 
required the disappearance of the ice age. So whatever effect 
precession has had, it has been obscured so as not to be traceable 
in the vegetation of today. It must be conceded, however, that 
there was land. ; 
The terrestrial changes in the flora, as I have said, are of 
the vegetation which has been turned into coal, and in hydrocar- 
bons and lime beds which are buried in the earth: also erosion has 
been gradual. These three causes have almost completely altered 
the vegetation of the land. 
The paroxysmal changes are those due to alteration of the 
surface of the land, due to earth folds, and are the most important 
of all in relation to the vegetation of today, while the other chang- 
es noted are the most important in geological history. 
It is a practical certainty that vegetable life began in the a 
at the poles, for that is where the first temperature cool enoug 
for vegetable life would be found. This life gradually extended 
temperature 
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The Carboniferous Age, which, compared with today, was 
very early in the earth’s history, was remarkable for the salsa 
development of land vegetation in quantity which has never been 
