CHAPTER VII 



THE UPPER PALEOZOIC FLORAS, THEIR SUCCESSION 



AND RANGE' 



DAVID WHITE 



CONTENTS 

 Stratigraphic Value of Land Plants 

 The Devonian Floras 

 Middle Devonian 

 Upper Devonian 

 The Carboniferous Floras 



Mississippian ("Lower Carboniferous") 

 Pennsylvanian ("Upper Carboniferous") 

 Westphalian (Pottsville and Allegheny) 

 Stephanian (Conemaugh and Monongahela) 

 Permian 

 "Permo-Carboniferous" Climates 



STRATIGRAPHIC VALUE OF LAND PLANTS 



Diastropkism and floral changes.— Tht terrestrial plant is insepa- 

 rably dependent on the conditions, not only of the soil and the water, 

 but also of the air from which it derives an important part of its sub- 

 stance. Any change, therefore, in the climatic, terrestrial, or water 

 conditions of its environment directly affects the plant and causes 

 morphologic changes to a greater or less degree, the greater plant 

 variations corresponding usually to the greater environmental changes. 

 The great floral revolutions of geologic history are connected with the 

 great diastrophic movements. 



Sensitiveness of land plants to complicated environment. — The land 

 plant, being essentially without the power of locomotion except by 

 accidental dispersion of its progeny, is most vitally susceptible to 

 changes in composition, temperature, etc., of its environmental 

 elements. Accordingly it constitutes a most sensitive indicator of 

 changes in these elements. The more highly organized the type the 



I Published by permission of the director of the U. S. Geological Survey. 



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