GENERAL LAWS OF ORIGIN AND MIGRATION. 241 



fair inference that the northeastern end of the Appala- 

 chian ridge was the original birthplace or centre of crea- 

 tion of what we may call the later Palseozoic flora, or of 

 a large part of that flora." 



"When my paper was written I had not seen the ac- 

 count published by the able Swiss palseobotanist Heer, of 

 the remarkable Deyonian flora of Bear Island, near Spitz- 

 bergen.* From want of acquaintance with the older 

 floras of America and western Europe, Heer fell into the 

 unfortunate error of regarding the whole of Bear Island 

 plants as Lower Carboniferous, a mistake which his great 

 authority has tended to perpetuate, and which has even 

 led to the still graver error of some European geologists, 

 who do not hesitate to regard as Carboniferous the fossil 

 plants of the American deposits from the Hamilton to 

 the Chemung groups inclusive, though these belong to 

 formations underlying the oldest Carboniferous, and char- 

 acterised by animal remains of unquestioned Devonian 

 age. In 1872 I addressed a note to the Geological Society 

 of London on the subject of the so-called " Ursa stage " 

 of Heer, showing that, though it contained some forms 

 not known at so early a date in temperate Europe, it was 

 clearly, in part at least, Devonian when tested by North 

 American standards ; but that in this high latitude, in 

 which, for reasons stated- in the report above referred to, 

 I believed the Devonian plants to have originated, there 

 might be an intermixture of the two floras. -Sut such a 

 mixed group should in that latitude be referred to a 

 lower horizon than if found in temperate regions. Dr. 

 Nathorst, as already stated, has recently obtained new 

 facts which go to show that plants of two distinct hori- 

 zons may have been intermixed in the collections sub- 

 mitted to Heer. 



* " Transactions of the Swedish Academy," 1871 ; " Journal of the 

 London Geological Society," vol. xxviii. 



