GENERAL LAWS OF ORIGIN AND MIGRATION. 239 



Between 1860 and 1870 the writer was engaged in 

 working out all that could be learned of the Devonian 

 plants of eastern America, the oldest known flora of any 

 richness, and which consists almost exclusively of gigantic, 

 and to us grotesque, representatives of the club-mosses, 

 ferns, and mares'-tails, with some trees allied to the cycads 

 and pines. In this pursuit nearly all the more important 

 localities were visited, and access was had to the large 

 collections of Prof. Hall and Prof. Newberry, in New 

 York and Ohio, and to those made in the remarkable 

 plant-bearing beds of New Brunswick by Messrs. Matthew 

 and Hartt. In the progress of these researches, which 

 developed an unexpectedly rich assemblage of species, the 

 northern origin of this old flora seemed to be established 

 by its earlier culmination in the northeast, in connection 

 with the growth of the American land to the southward, 

 which took place after the great Upper Silurian subsi- 

 dence, by elevations beginning in the north while those 

 portions of the continent to the southwest still remained 

 under the sea. The same result was indicated by the 

 persistence in the Carboniferous of the south and west of 

 old Erian forms, like Megalopteris. 



When, in 1870, the labours of those ten years were 

 brought before the Royal Society of London, in the 

 Bakerian lecture of that year, and in a memoir illustrat- 

 ing no less than one hundred and twenty-five species of 

 plants older than the great Carboniferous system, these 

 deductions were stated in connection with the conclusions 

 of Hall, Logan, and Dana, as to the distribution of sedi- 

 ment along the northeast side of the American continent, 

 and the anticipation was hazarded that the oldest Palaeo- 

 zoic floras would be discovered to the north of Newfound- 

 land. Mention was also made of the apparent earlier 

 and more copious birth of the Devonian flora in America 

 than in Europe, a fact which is itself connected with the 



ater northward extension of this continent. 



