CHAPTER I. 
Ch PAChOuUS FOSS PLANTS 
FROM MINNESOTA. 
BY LEO LESQUEREUX. 
In looking over the long series of the groups of plants which have inhabited the 
earth at the divers periods of its evolution, none appear so remarkable, none excite 
so much of interest and stimulate so forcibly the mind to researches by problems of 
importance and magnitude, as that of the Middle Cretaceous known in North America 
as the flora of the Dakota group. 
The geological area occupied by the formation, its thickness and the constitution 
of the rocks are well known.* Some portions of its flora have been already 
described by European and American authors in more or less complete memoirs 
which have put in evidence the great variety and luxuriance of its constituents. It 
seems, therefore, that the vegetation of that period should be satisfactorily known, 
from the fossil remains which have been determined until now, but, nevertheless, 
every new research in this field brings forth some facts which contribute to more 
evidently expose the peculiar character of the flora and its wonderful diversity. 
Though the above assertion has been made already at different times, it is now 
suggested again, by the examination of some lots of specimens procured in Minne- 
sota, representing a number of species, which, described below, give occasion to some 
remarks upon the origin, the distribution and the peculiar characters of the vegeta- 
tion prevalent during the period of the Middle Cretaceous, generally known as the 
Cenomanian. 
In the present stage of its progress, vegetable paleeontology has discovered evi- 
dent traces of land vegetation as far down as the Middle Silurian. The most ancient 
remains of land plants represent species of the three orders, composing the class of 
the Acrogens or cryptogamous vascular plants, viz: the Eyuisetacee, the Filices (or 
*See for what relates to the geographical and stratigraphical distribution of the Dakota Broun: F. V. Hayden's 
reports of the United States Geological Survey of the Territories, “Vol. VI, Cretaceous Flora, pp. 13- 
