DAVID WHITE 
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THE CARBONIFEROUS FLORAS 
MISSISSIPPIAN (“‘LOWER CARBONIFEROUS”’) 
Characters—The step from the Upper Devonian flora to that of 
the Mississippian (“‘ Lower Carboniferous”’) is marked by a floral con- 
trast which, in some regions, is unexpectedly sharp though the warping 
of the Devonian floor to form the new Carboniferous synclines and 
the contraction of the seas naturally premise distinct climatic as well 
as other environmental changes. ‘The new flora which lived in the 
restricted basins of the early Mississippian consists of Triphyllopteris, 
the broad, large-pinnuled Aneimites, the linear (flaccida) type of 
Sphenopteris, Cyclostigma, Eskdalia, and the acuminate Lepido- 
dendra chiefly of the corrugatum group. 
Lowest stage—Pocono.—The early Mississippian was a time of 
sea expansion; and in a number of distant areas, such as the northern 
part of the Appalachian trough, northern Alaska, the eastern Arctic, 
Scotland, and southern Siberia, the conditions at this moment were 
favorable for the formation of considerable coals. 
Source.—Since the vegetation was presumably most luxuriant in 
these regions of coal formation, and since greatest evolution of forms 
attends most rapid and luxuriant expansion of a flora, we are perhaps 
safe in supposing that these are probably the regions of evolution of 
the flora as a whole. 
Regional differences—In this connection it may be noted that, 
either on account of land or marine barriers, or because the climatic 
conditions throughout the northern hemisphere may at the outset have 
been less uniform than in the preceding epoch, the different areas 
exhibit more or less distinct local floral differences. ‘Thus in the 
Pecono of West Virginia and Eastern Pennsylvania where Triphyl- 
lopteris and the corrugatum type of Lepidodendron are almost without 
competition, the former achieved a remarkable differentiation far sur- 
passing that known in any other area. In Nova Scotia, on the other, 
hand, the Horton series, which I regard as practically contempo- 
raneous with the Pocono, contains the same Lepidodendra, accom- 
panied, however, by Aneimites instead of Triphyllopteris. In both 
these regions the formations are in close relations with the Upper 
Devonian—in fact, probably in continuous sequence at one point or 
another. But the Pocono flora is apparently nearer to the Arctic 
