PREFACE. 



tween the northern and southern portions of the Union, 

 the proximity of the lower portion of it to the coast, a 

 water boundary of 50 miles, streams penetrating the interior, 

 with shores alternately covered and left bare by the tides, 

 the variety of surface it presents, rugged hills, level plains, 

 extensive meadows, sphagnous swamps, vast marshes, and 

 almost every variety of soil to be found east of the Alle- 

 ghany Mountains. 



The compiler takes pleasure in acknowledging his in- 

 debtedness to Prof. A. Gray, of Cambridge; Dr. W. Dar- 

 lington and Joshua Hoopes, of West Chester, Pa.; Dr. E. 

 Michener, of New Garden, Pa.; Dr. G. Engelmann, of St. 

 Louis, and others, for their kind assistance in the prepara- 

 tion of the Catalogue. 



Appended are the names of a number of plants which 

 may probably be found within our limits. This will at 

 least show that completeness is not claimed for the present 

 Catalogue. We are well aware that much remains to be 

 done in the way of exploration, and are sure that efforts 

 to extend the list would not be unsuccessful. 



We are pleased to be able to add a list of species of 

 Diatomacea3 and Desmidiese, identified by Mr. Christian 

 Febiger, of Brandywine, as existing in the vicinity of 

 AVilmington. Whilst so much remains to be done in this 

 attractive and comparatively unexplored field of micro- 

 scopic research, we feel sure that any contribution to our 

 knowledge of species and localities will be acceptable to 

 observers elsewhere, and hope that it may both stimulate 

 and facilitate the inquiries of others at home. 



E. T. 



Wilmington, April 2f>, 1- 



