lxxxviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [vol. lxxix, 



Middle Devonian plants, but almost to see them growing as a 

 green carpet slowly spreading over the waters of a marsh- encircled 

 lake. The information thus gained can, in some measure at least, 

 be used as an aid in the interpretation of specimens from other 

 localities preserved as impressions, and in themselves affording 

 little evidence of their true nature. 



Newberry's words stimulate the imagination : the realization of 

 the ' spirit of the movement ' would give us the clue to the 

 mystery of evolution. This is not an appropriate occasion for a 

 lengthy excursus into the realms of speculative botany ; but a few 

 general questions may be briefly considered. What conclusions 

 can be drawn, from a general review of the palseobotanical records 

 furnished by Devonian rocks throughout the world, as regards (1) 

 the measure of the progress of evolution afforded by a comparison 

 of the floras which flourished at different stages of the Devonian 

 period; (2) the geographical distribution of plants during the 

 Devonian Period ; and (3) the origin of terrestrial vegetation, and 

 the history of the evolution of the different classes of land-plants ? 



In 1916 Dr. T. G. Halle expressed the opinion that there is a 

 far greater difference between the Lower Devonian flora of Roragen 

 in Norway and those of Upper Devonian age, than between the 

 latter and the Lower Carboniferous. Arber wrote : 



' It is now clear that in Devonian times two terrestrial floras, quite distinct 

 as regards affinity, existed, one in the earlier part, and one in the latter 

 portion of the Devonian Period.' 



The former he named the Psilophyton Flora, and the latter the 

 Arcliceopteris Flora. The majority of Lower Devonian plants are 

 from the Gaspe Peninsula, Norway, and Scotland; a few are 

 recorded from Belgium, the North of France, the Buland Archi- 

 pelago off the western coast of Norway, the Falkland Islands, and 

 one species from China. Middle Devonian plants have been 

 described from Canada, a few localities in the Eastern United 

 States, Scotland, Western Norway, Bohemia, and Germany. 

 While some genera are confined to one or other of these two 

 groups of Devonian floras, there is a general similarity of facies in 

 the older Devonian vegetation as a whole. On the other hand, the 

 Upper Devonian floras are not only much richer, but of a different 

 type. One of the richest and best-known later Devonian floras is 

 that of Bear Island within the Arctic Circle. Reference is made 

 later to other floras of this geological age. In more than one 

 region the line between Upper Devonian and Lower Carboniferous 



