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 

 PaliBozoic peiiod, it was shown that, to its close, the only ve<?etable 

 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 sjjccies, and the 

 lowest class of flowering plants (gymnosperms) of the same nature 

 as the pine and yew. The characteristic vegetation of the 

 Palii30zoic 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 descnbed as the true 

 Edenic period of the earth's history, when tlie 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 



