The Ohio Naturalist. 
[Vol. XI, No. 6, 
318 
record of plant life is poor (24). 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. 
Many plants exhibit a striking xerophily; the leaves are reduced 
to linear organs, the stomata have special constructions and are 
heavily 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 extermination 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 peaty 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 layers or sheets of limestone. The former are frequently 
crossbed'ded, 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 by the abundant fossils which 
they contain. The limestones are 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 
