THE GENESIS AND MIGRATIONS OF PLANTS 203 



if equalled in modern times, and which may have enabled 

 plants so constructed to exist even on the land. 



From these beginnings in the early Palaeozoic, the progress 

 of the vegetable kingdom went on, until, in the later parts of 

 that great period, the Devonian and Carboniferous eras, it 

 culminated in those magnificent forests which have left so 

 many interesting remains, and which accumulated the materials 

 of our great beds of coal. In these the families of the Club 

 mosses, the Ferns and the Mare's-tails attained to a perfection 

 in structure and size altogether unexampled in the modern 

 world, and may be said to have overspread the earth almost to 

 the exclusion of other trees.. Here, however, two new families 

 come in of higher grade, and leading the way to the flowering 

 plants. These are the Pines and their allies and the Cycads, 

 and certain intermediate forms, neither Pines nor Cycads, but 

 allied to both. 1 This wonderful flora, which we have now the 

 materials to reproduce in imagination almost in its entirety, 

 decays and passes away in the Permian system, the last portion 

 of the Palaeozoic, and in entering into the third great period of 

 the earth's history the Mesozoic, we again find an almost 

 entire change of vegetation. Here, however, we are able to 

 understand something of the reasons of this. The Palaeozoic 

 floras seem to have originated in the North, and propagated 

 themselves southward till they replenished the earth, and they 

 were favoured by the existence at that time of vast swampy 

 flats extending over great areas of the yet imperfectly elaborated 

 continents. The Mesozoic floras, on the other hand, seem to 

 have been of Southern or equatorial origin, and to have fol- 

 lowed up the older vegetation as it decayed and disappeared, 



1 Cordaites, etc. As I have elsewhere shown, these are distinct sub- 

 floras in the Lower, Middle and Upper Devonian, and in the Lower, 

 Middle and Upper Carboniferous and Permian, sufficiently different to 

 allow these periods to be determined by the evidence of these fossil 

 plants. Reports prepared for Geological Survey of Canada. 



