IV ADVERTISEMENT. 



The Appendix, which is added to the whole, consists of a catalogue 

 of North American genera of plants arranged according to the order in 

 the text, with the number of species belonging to each genus as far as 

 they are at present determined, besides several tables exhibiting the rela- 

 tive proportions of the different families, &c, and an index. The first 

 and only work of this kind, before the present was by the late distinguished 

 Abbe Correa, who prepared it for the use of a botanical class to which he 

 lectured in Philadelphia, in 1815.* It is entitled li Reduction of all the 

 Genera of Plants contained in the Catalogus Plantarum Americce 

 Septentrionalis of Dr. Muhlenberg, to the Natural Families of Jus- 

 sicii." At that time our Botany was but little known, and the Natural 

 System itself was in a very imperfect state. 



The catalogue which 1 have prepared, embraces a considerable num- 

 ber of genera and species which are not described in the latest general 

 Floras, but it is by no means asserted to be complete. There are exten- 

 sive districts in North America which have never been visited by a Bo- 

 tanist, and even in the United States there are large spaces which are but 

 little known or very imperfectly explored. There are also many plants 

 collected by Douglass, Richardson, Drummond, Scouler, Nuttall, and 

 others, which have not yet been published, so that it is probable that North 

 America, excluding the Mexican states, contains not less than 5000 pheno- 

 gamous plants. 



In preparing the list of cryptogamous genera, I have been kindly as- 

 sisted by my friends A. Halsey, Esq. and the Rev. L. D. Schweinitz. 

 The latter gentleman kindly alowed me to copy the genera of the Fungi 

 from his manuscript work on the North American species of this tribe, 

 which he lately offered to the Philosophical Society of Philadelphia, for 

 publication in their transactions. 



The mark (§) prefixed to a name in the catalogue signifies that the 

 plant has been introduced. A note of interrogation expresses a doubt 

 whether the genus is referred to the right natural order. The numbers 

 following the orders refer to the pages of the Introduction. J. T. 



New York, November 4, 1831. 



* It was published without a name in a pamphlet form, and was afterwards re- 

 printed in the American edition of Smith's Grammar of Botany, where it is incor- 

 rectly stated to have been written by Dr. Muhlenberg. 



