3i8 The Ohio Naturalist. [Vol. XI, No. 6, 



record of plant life is poor (2-1:). But enough fossil vegetation has 

 been recovered in the surrounding states to show that all the lead- 

 ing groups of the Devonian flora were represented with an asso- 

 ciated insect life. The different areas exhibit distinct floral and 

 growth-form differences, and suggest either barriers or differences of 

 water content in the soil. The plant associations are varied and 

 of several aspects. The vegetation is remarkably cosmopolitan 

 in distribution which would premise the absence of climatic zones. 

 Alany plants exliibit a striking xerophily; the leaves are reduced 

 to linear organs, the stomata have special constructions and are 

 heavih^ coated and hardened; the stems show development of 

 water storage tissue; the roots are extended horizontally. The 

 general desiccation effects of the habitat resulted, however, not 

 in the extennination of plants favoring free water, but in the lim- 

 itation of their functional activity to periods of moist or rainy 

 seasons and in the increase of functional responses. The differen- 

 tiation has become a factor in distribution and has given the 

 plants a greater range of dispersal; the new place-functions had a 

 survival value in the competitive struggle among the organisms, 

 and in the environmental selection. These phenomena, as will be 

 shown below, are not suggestive of greater severity of climate, but 

 indicate unfavorable conditions in the peat}^ substratum of the 

 marshes. 



The era was brought to a close by an emergence of consid- 

 erable areas of shallow lowland which with their vegetation con- 

 stitute the great Carboniferous or Pennsylvanian system and 

 its important Coal-measures. The land area of Ohio grew in 

 spite of the fact that it was periodically depressed and degraded. 

 The withdrawal of the sea ultimately resulted in the union of 

 separate land masses and the extension to its present borders. 

 The formations are a series of beds somewhat unlike any hereto- 

 fore considered. Irregularly distributed through the Carbonif- 

 erous series are six or eight strata of sandstone, part of them con- 

 glomerates, characterized by the presence of quartz pebbles which 

 sometimes are of large size. Next to them are beds of shale in 

 great variety of colors; they are frequently replaced with sand- 

 stone la3^ers or sheets of limestone. The former are frequently 

 crossbedded, the agents of deposition being rivers or the wind; the 

 latter are all of them thin and partly of fresh water origin, and 

 partly of marine origin as is shown b}' the abundant fossils which 

 they contain. The limestones ai^e in many cases deposits of a 

 calcareous nature, and frequently associated with beds of iron ore 

 or with a layer of clay of varying degree of purity. The clays are 

 always overlain with seams of coal ranging from a mere black line 

 to a dozen feet and more in thickness. Each of these coal seams 

 stands for a former low and undrained land surface and its vegeta- 

 tion cover. The well-marked order of arrangement of the strata 



