CLIMATOLOGY OF THE LATE PALEOZOIC 239 



protection of the stomata on the leaves of Sigittaria; and for the water-storage 

 tissue in the trunk of Lepidodendron all swamp types. 



"As the Conemaugh is apt to be marked by the deposition of thick red beds, 

 especially in the Appalachian trough, it would at first seem that the characters 

 of the flora only confirm the explanation that redness resulted from aridity. 

 However, in opposition to such a conclusion it must be noted that (a) the flora 

 in the red beds has not been observed to differ very markedly from that in the 

 regions of dark contemporaneous sediments, including coal; (b) the plants, though 

 less varied, are not reduced in size, nor possibly, in number; (c) coal, usually 

 thin, to be sure, occurs in the midst of the red beds of the Conemaugh both in the 

 eastern and the Rocky Mountain regions of America, as well as in Europe, some 

 of the coal being thick; (d) the evidence of seasonal growth ('annual rings') in 

 the Conemaugh woods yet examined is slight, though the rings are a little more 

 distinct than in the Allegheny woods; (e) the great calamitean growth appears 

 unimpeded, though many of the giant species are provided with thick xylem 

 and cortex; (/) the nearest living relatives of the Psaronii, the Marratiaceae, 

 are now exclusively tropical. In view of these facts it is evident that in the 

 Conemaugh the climate was still mild and practically free from frost, and that the 

 rainfall was at times certainly ample for the production of peat under fresh-water 

 conditions. The absence of coal at other levels may, as in other series, be largely 

 due to lack of proper adjustment of bottom and water-level. 



"Granting that the Calamaria^ were swamp plants, and that many other 

 types, including the enormous Sigillaria, were also inhabitants of the marsh, it 

 still remains obvious that aridity was not sufficiently developed to dry up all 

 the swamps. Bearing in mind also the protection of the stomata in the lycopods 

 and Calamariae, and the villous development of the Pecopteris species, the water- 

 storage equipment of many of these types, including the tree ferns, the develop- 

 ment of waxy covers in some Neuropteris species, and the presence of resin canals 

 and other secretory cells in many of the ferns, cycadofilices, lycopods, and 

 Calamaris, or, in fact, that the gymnospermous woods were perhaps of kinds less 

 affected by dry seasons, it nevertheless is evident that in general the rainfall was, 

 at certain stages at least, sufficient, even at warm temperatures, to permit coal 

 formation over great areas in nearly every coal field. It seems not improbable 

 that during most of Conemaugh time the total rainfall was distinctly less than in 

 Allegheny time, and it is possible that for brief intervals the climate may 

 have been dry as compared to the latter; but it appears improbable that during 

 ordinary red-bed deposition say, in the Appalachian trough the climate even 

 closely approached aridity as that term is employed in reference to present-day 

 conditions. Such intervals must have wrought greater changes, more sweeping 

 extinctions in the flora. From the paleobotanical standpoint the widely current 

 belief that aridity in the actual sense is to be assumed as causally and almost 

 indispensably associated with red-bed deposition is not well founded. The 

 generalization seems to be too broad and too sweepingly applied. In this connec- 

 tion it may be noted that although in the Broad Top and the Potomac basins 

 red beds are almost absent, redness of color extends diagonally downward into 

 the top of the Allegheny, which is still coal-bearing, near the Kentucky-West 

 Virginia line in the Kenova quadrangle. Withal it must not be forgotten that 

 the xerophytic characters are, perhaps, confined to aquatic or swamp plants, and 

 that the protections are exactly those adopted by bog plants of today to insure 

 against exposure to too great loss of water, or to increased toxicity of the sub- 

 stratum resulting from an unusual reduction of the water cover. 



