TRANSACTIONS. 219 
in them, might reasonably be taken to indicate the previous exist- 
ence of plant life, as we knew of no other source of unoxidised 
carbon than what is furnished by plants. Passing onwards to the 
Paleozoic period, it was shown that, to its close, the only vegetable 
remains that had been discovered were those of plants allied to 
the humble club-mosses of the present day, then, however, assum- 
ing the dimensions of lofty trees, other gigantic plants related to 
the equiseta or horsetails, ferns in innumerable species, and the 
lowest class of flowering plants (gymnosperms) of the same nature 
as the pine and yew. The characteristic vegetation of the 
Paleozoic period died out in the Permian formation, and the 
flora of the early Mesozoic was at first transitional, although 
there was no great advance. However, about the end of the latter 
period, whether from a gap in the record, or from whatever cause, 
there appeared a sudden and wonderful incoming of the higher 
classes of the vegetable kingdom, including the existing genera, 
so that the aspect of the flora was the same as that of the present 
day, though it was much more varied, and cryptogams and 
gymnospermous phanerogams sank into the subordinate position 
they now occupy. This has been justly described as the true 
Edenic period of the earth’s history, when the dry land was 
clad, perhaps from the very Pole, at least from the latitudes of 
Greenland and Spitzbergen, with an exuberant growth of foliage, 
flower, and fruit, accompanied by a remarkable uniformity of 
temperature throughout the globe. It was a noteworthy fact that 
the successive vegetable forms which have from time to time over- 
spread the earth’s surface appear to have originated within the 
polar circle, and this might now be regarded as established. 
Throughout the greater part of the Tertiary period, the land, in the 
northern hemisphere at least, continued to increase, and was 
tenanted by the “noblest vegetation and the grandest forms of 
mammalian life the earth ever witnessed.” But towards its close 
a gradual refrigeration set in—the ‘great ice age” was approach- 
ing. Slowly, but surely, the ice and snow which formed in the now 
frozen zone spread downwards, until even within the tropics 
glaciers filled the mountain valleys, and the rich and multiform 
Tertiary flora was either destroyed or driven towards the 
equatorial region. This wintry period having at length come to 
an end, the exiled plants straggled back to their native soil, a sadly 
diminished band. The thick-ribbed ice that burdened so large a 
portion of the polar and temperate zones did not, they might be 
