PREFACE. PP. ix 



horizon. The strata are mostly of a material which soon 

 breaks down into clay and loose matters which obscure the 

 outcrops. Beside this, there has been much surface action, 

 and owing to the depth to which decomposition has pene- 

 trated it is very difficult to get sound material. These 

 causes have prevented us from procuring from the upper- 

 most beds such a collection as we wished ; hence we cannot 

 claim to present, from this portion of the field, such com- 

 prehensive details as from the Waynesburg coal bed. Still. 

 we have plants from widely separated localities and hori- 

 zons in this upper portion, and they suflfice to give import- 

 ant indications of the character of its tiora. 



As we made our collections ourselves we had opportuni- 

 ties to study the plants in situ, and to examine and com- 

 pare a large amount of material which we could not have 

 had if the collecting had been done by others. 



In the preparation of our work we are indebted to Prof. 

 Newberry, of Columbia College, New York, for the use of 

 books, and especially to Prof. Lesquereux of Columbus, 

 Ohio, for the liberal loan of many works not otherwise ac- 

 cessible to us. 



Mr. G. Gutenberg and Prof. Mertz, of Wheeling, W. Va. 

 have kindly loaned to us, for the purpose of comparison, 

 specimens of plants collected by them from the horizon of 

 the Pittsburg coal, near Wheeling. Mr. T. L. Hazzard, of 

 Washington and Jefferson College, Penn., also loaned us 

 plants collected by him from the Upper Barrens of Penn- 

 sylvania. To all these gentlemen we return our thanks. 



The Authors. 



W. Va. University, 



MORGANTOWN, W. Va., JuTie ^5, 1878. 



Note. — The order of our names on the title page has no significance, as we 

 are equally and jointly responsible for this work. 



The Authors. 



