510 r. H. KNOWLTON EVOLUTION OF GEOLOGIC CLIMATES 



York^ where it has been studied by Dr. John M. Clarke. There is no 

 indication, however, that this affected the temperature of the oceans as 

 reflected by marine life. Concerning this point Dr. Clarke writes me 

 as follows: "Data from the invertebrate marine faunas are not merely 

 negative. I think they are constructively positive in favor of absence 

 of climatic zones ; that is to say, in the main corroborative of your gen- 

 eral proposition of a uniform undifferentiated climate .^^ 



Recently Mr. G. F. Matthew ^ has published a paper under the title, 

 "Were there climatic zones in Devonian time?^^ in which he attempts to 

 show that there are marked ecological differences between certain floras 

 of the eastern United States and Canada, on which he predicates the 

 climatic differences. But this is based on material that comes from beds 

 of undoubted Carboniferous age which are compared with plants of un- 

 doubted Devonian age — the perpetuation of an error to Avhich the author 

 has long been wedded. No further discussion of this contention seems 

 necessary. 



Carboniferous' floras. — In general. — During Carboniferous time plant 

 life had become so abundant, so diversified, and so widely dispersed over 

 the globe that a complete analysis of this flora in all its phases would 

 demand far more space than is at command, hence only an outline of the 

 salient facts bearing on the question of climatic conditions can be at- 

 tempted. Although there have been some differences of interpretation 

 there seems now to be substantial agreement on the essential points under 

 discussion, namely, that there was an abundant supply of moisture, n 

 wide distribution with little indication of climatic zones or marked 

 botanical provinces, and that the climate was equable. This leaves open 

 for consideration the fixation, if reasonably possible, of the probable 

 temperature range. 



Mississippian floras. — It might be presumed that in passing from the 

 Devonian into the Mississippian there Avould.be a gradual merging of 

 plant forms, but in certain regions, at least, there is found to be a quite 

 unexpectedly sharp difference in the floras. The early Mississippian was 

 a time of sea expansion, and in many widely scattered parts of the world 

 conditions became favorable for the formation of coal. This new flora, 

 which, according to White, 



"lived in the restricted basins of the early Mississippian consists of Triphyl- 

 lopteris, the broad, large-pinnuled Aneimites, the linear type of Sphenopteria, 

 Cyclostigma, Eokdalia, and the acuminate Lepidodendra chiefly of the cori'u- 

 gatum group. . . . 



G. F. Matthew : Trans. Roy. Soc. Canada, 3d ser., vol. 5, sec. 4, 1911, pp. 125-153. 



