492 PALAEONTOLOGY OF ILLINOIS. 



remarks would seem also to authorize an affirmative answer to the often pro- 

 posed questions : 



1st. Does what we already know of the Coal Measures give us a just idea of 

 the boggy vegetation of which the coal is a compound ? 



2d. Is the vegetation of the bogs of the coal a true representation of the 

 whole flora of the epoch ? 



For though it is argued, with an appearance of right, that the whole flora 

 of the Carboniferous time could not have been limited to that of the swamps, 

 that a part of the land was high and dry, and as we have now, on our peat 

 bogs, a peculiar group of plants appropriate to that kind of soil, and without 

 analogy to the vegetation of our dry land, the same differences should have 

 existed at the time of the formation of the coal. The contrary proposition, 

 considered hypothetically, could be equally well sustained. From all appear- 

 ances, the land, especially on our western coal fields, was, at the Carboniferous 

 period, represented merely by a series of flat swamps, separated by lagoons, 

 and therefore the whole vegetation of the land was essentially of the boggy kind. 

 But, even if at this epoch there was any elevated land, the extreme atmospheric 

 humidity should have forced upon it the same vegetation as that of the bogs, 

 as it happens at our time in some parts of Ireland and Germany, where, under 

 the influence of atmospheric humidity, peat bogs ascend on inclined slopes to 

 the top of high mountains. Prof. Schimper says, in speaking of the ferns 

 which constitute the essential vegetation of the coal formations : there is no 

 other natural order of plants whose intensity of vegetation so much depends 

 upon atmospheric humidity. Ferns are true natural hygrometers, whose indi- 

 vidual as well as numerical development is always in direct proportion to the 

 humidity of the climate wherein they live. Therefore, the land vegetation of 

 the Carboniferous period must everywhere bear the same general character. 

 A confirmation of this assertion seems also to be found in the fact, that even 

 in the formations of great thickness of Nova Scotia, where trees are seen stand- 

 ing and imbedded at different altitudes, and where no coal is seen in connec- 

 tion with them, these trees are recognized as belonging to species, or at least 

 to genera of the coal : Sigillaria, Lepidodendron and Catamites. But on the 

 other hand, we have to account for the presence in the slate and sandstone 

 overlying our coal strata, of various kinds of fruits or hard nuts, whose relation, 

 for some of them at least, can not be traced to any species of the coal flora 

 known by other kinds of remains: leaves, stems, etc. It is true that as fast 

 as our acquaintance with this ancient vegetation becomes more intimate, some 

 of these so-called fruits are recognized as peculiar vegetables of the coal, for 

 example, some species of Trigonocarpum or Carpolithes, as tubercles of Equi- 

 setacese, or as vesicular appendages grown at the end of leaves of Stigmaria. 

 But an explanation of this kind can not be admitted for nutlets, representing 



