92 SISTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



9. THE FLORA OF THE DEVONIAN PERIOD. 



It is only within a comparatively recent period, that we have 

 learned to look for a distinct and well-marked Flora in the Devo- 

 nian rocks of this country; or, in other words, in the rocks of the 

 Hamilton, Portage and Chemung groups, with their subordinate 

 beds. During the Geological Survey of New- York, when for the 

 first time the sequence of the formations was determined, it was 

 likewise ascertained that remains of land-plants characterized 

 certain of these formations. The greater part of them, it is true, 

 were fragmentary, and those which were in more perfect con- 

 dition were recognized as of known Carboniferous genera. At 

 that time so little was known of any flora older than that of the 

 Carboniferous period, that reasonable doubts were entertained 

 whether these plant-bearing beds, with Ferns and Stigmaria, par- 

 ticularly of the Chemung group, were not of true Carboniferous 

 age. Nor has this idea been entirely banished by a more complete 

 knowledge of the Fauna of the period, which continued investiga- 

 tions have made known. 



While the limits between the Carboniferous and Devonian for- 

 mations have been very clearly made out along the borders of 

 New- York and Pennsylvania, both by the physical features and 

 carefully studied limits of formations, as well as by the fauna, 

 there has arisen a question as to the relative age of certain beds 

 in Ohio and other Western States. Although the study of the 

 Flora of the Pre-carboniferous rocks of Canada, New-Brunswick, 

 Maine, New- York, and to some extent Ohio, offers a very satis- 

 factory solution of the problem, we are deprived of this means of 

 identification in more western localities. Whatever may be the 

 final determination as to the age of the strata underl3^ing the 

 Coal conglomerate of Central and Southern Ohio, and those of 

 Michigan, Indiana, Illinois and Iowa, which directly underlie the 

 well-marked Carboniferous limestone, the investigation is likely 

 to receive little aid from the Flora. Few or no land-plants occur 

 over the greater part of this area, so far as at present known ; 

 while the Fauna is much more abundant than that of the Chemung 

 rocks of New-York. 



