224 THE GENESIS AND MIGRATIONS OF PLANTS 



they ever were, and some genera would seem even to have 

 increased in number of species, though on the whole the flora 

 of our modern woods is much less rich than those of the 

 Miocene and Eocene, or even than that of the Later Cre- 

 taceous. The early Tertiary periods were, as we know, times of 

 exuberant and gigantic animal life on the land, and it is in con- 

 nection with this that the vegetable world seems to have 

 attained its greatest variety and luxuriance. Even that early 

 post-glacial age in which primitive man seems first to have 

 spread himself over our continents was one richer both in 

 animal and plant life than the present. The geographical 

 changes which closed this period and inaugurated the modern 

 era seem to have reduced not only the area of the continents 

 but the variety of land life in a very remarkable manner. Thus 

 our last lesson from the genesis and migrations of plants is 

 the humbling one that the present world is by no means the 

 best possible in so far as richness of vegetable and animal life 

 is concerned. 



Reference has been made to the utility of fossil plants as 

 evidence of climate ; but the subject deserves more detailed 

 notice. I have often pondered on the nature of" the climate 

 evidenced by the floras of the Devonian and Carboniferous; but 

 the problem is a difficult one, not only because of the peculiar 

 character of the plants themselves, so unlike those of our time, 

 but because of the probably different meteorological conditions 

 of the period. It is easy to see that a flora of tree-ferns, great 

 lycopods and pines is more akin to that of oceanic islands in 

 warm latitudes than anything else that we know. But the 

 Devonian and Carboniferous plants did not flourish in oceanic 

 islands, but for the most part on continental areas of consider- 

 able dimensions, though probably more flat and less elevated 

 than those of the present day. They also grew, from Arctic 

 latitudes, almost, if not altogether, to the equator ; and though 

 there are generic differences in the plants of these periods in 



