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 Calcimites. 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 Tngqnocarpum or Carpolithcs, as tubercles of Equi- 
aetacese, 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 
