1877.] tJUt fLesquereux. 



On the Progress of the North American Carioniferous Flora, in prepara- 

 tion for the Second Geological Survey of Pennsylvania. 



By L. Lesquereux. 



{Bead before the American Philosophical Society, January 5, 1877.) 



The purpose of this memoir is to give a short account of the progress 

 which has been made, to this day, in the preparation of the North Ameri- 

 can Coal Flora as one volume of the current Keports of the Second Geo- 

 logical Survey of Pennsylvania. 



At, first it seemed appropriate to prepare for publication, and in order to 

 preserve the right of priority of names, a catalogue of the species which 

 have to be described in the Flora, and to define the essential points of the 

 classification, especially the generic divisions. 



Details of classification, however, cannot be positively fixed before 

 all the materials used in the preparation of the descriptions of the species 

 have been definitely examined. Then the manuscript of the flora will be 

 ready for the printer and a synopsis of it would be useless. Moreover, a 

 mere enumeration of names would offer little of general interest. 



It is therefore more advisable to give in advance an expose of the plan 

 which has been followed in the researches deemed necessary for the pre- 

 paration of the work ; of the available sources of information ; of the ma- 

 terials, when and where collected for it ; of the point arrived at until now, 

 and, therefore, of the more interesting data which have to be exposed in 

 the publication of this Flora. 



Those who have ever examined what is generally called specimens of coal 

 plants, know that they generally represent parts of trunks, whose surface is 

 marked by peculiar impressions; or branches without leaves, whose relation 

 is recognized also by the scars upon their bark; or, for the ferns, especially, 

 fragments or pinnae of fronds will leaflets, or more generally, of detached 

 pinnules, which, though they may be beautiful, do not give, when con- 

 sidered separately, an idea of the general or true character of the vegetable 

 to which they belong. The classification of the living species of the great 

 family of the ferns is derived more especially from the characters of their 

 fructifications. In the coal, though the ferns constitute by far the greatest 

 part of the vegetation, their fructifications are rarely found, and when found, 

 they are mostly attacho'd to branches or pinnae separated from the sterile 

 fronds, which then, were, as they are now, of.en very different in aspjct 

 and characters fi'om the fruiting ones. Hence it is very difficult to ascertain 

 tliL'ir correlation ; and thus the paleobotanist may place in one genus a sterile 

 branch when he has to describe the fertile pinna of the same tern, in another. 

 Long ribbon leaves, hard fruits of various shape, also are frequently seen 

 in the shale of the coal ; but these are most rarely, if ever found attached 



PTiOC. AMER. PHILOS. 80C. XVI. 99. 2x 



