388 THE CANADIAN NATURALIST. [Vol. viii. 



The plants described by those gentlemen from the Old Red 

 Sandstone of Callender, I should suppose, from their figures and 

 descriptions, to belong to the genus Arthrostigma, rather than 

 to PsilopJiyton. I do not attach any importance to the sugges- 

 tions referred to by them, that the apparent leaves may be leaf- 

 bases. Long leaf-bases, like those characteristic of Lepidofloyos, 

 do not occur in these humbler plants of the Devonian. The 

 stems with delicate " horizontal processes " to which they refer 

 may belong to Ptilophyton or to Pinnularia. 



In conclusion, I need scarcely say that I do not share in the 

 doubts expressed by some British Palaeontologists as to the dis- 

 tinctness of the Devonian and Carboniferous Floras. In Eastern 

 America, where these formations are mutually unconformable, 

 there is, of course, less room for doubt than in Ireland and in 

 Western America, where they are stratigraphically continuous. 

 Still, in passing from the one to the other, the species are for 

 the most part different, and new generic forms are met with, 

 and, as I have elsewhere shown, the physical conditions of the 

 two periods were essentially different.* 



It is, however, to be observed that since, as Stur and others 

 have shown, Calamites radiatus and other forms distinctively 

 Devonian in America, occur in Europe in the Lower Carboni- 

 ferous, it is not unlikely that the Devonian Flora, like that of 

 the Tertiary, appeared earlier in America. It is also probable, 

 as I have shown in the Reports already referred to, that it ap- 

 peared earlier in the Arctic than in the Temperate zone. Hence 

 an Arctic or American Flora, really Devonian, may readily be 

 mistaken for Lower Carboniferous by a botanist basing his cal- 

 culations on the fossils of temperate Europe. Even in America 

 itself, it would appear from recent discoveries in Virginia and 

 Ohio, that certain Devonian forms lingered longer in those 

 regions than further to the North-east ;f and it would not be 

 surprising if similar plants occurred in later beds in Devonshire 

 or in the South of Europe than in Scotland. Still, these facts, 

 properly understood, do not invalidate the evidence of fossil 

 plants as to geological age, though errors arising from the neglect 

 of them are still current. 



* Reports on Devonian Plants and Lower Carboniferous Plants of 

 Canada. 



f Andrews, Palaeontology of Ohio, Vol. II. Meek, Fossil Plantg 

 from Western Virginia, Philos. Society, Washington, 1875, 



