it lias been necessary, in many instances, to alter andanriend 

 the characters of genera and species as they were described 

 in previous works, and also to make some changes in 

 nomenclature. He is well aware of the, great inconvenience 

 of changing established names, but this must necessarily be 

 done while botany is an advancing science. A large pro- 

 portion of our plants have not been examined since botany 

 has assumed a philosophical character : hence they have been 

 imperfectly described, and, in many instances, referred to 

 wrong genera and species. We are, therefore, often under 

 the necessity of using erroneous names, or of changing thena 

 for such as are more appropriate. It appears to us that the 

 interest of science requires us to adopt the latter alternative ; 

 but, at the same time, to make no alteration except such 

 as the natural progress of botany renders necessary. There 

 can be little doubt that Linnceus himself, had he lived to 

 this day, would have materially altered both his system 

 and nomenclature ; as he did in each successive edition of 

 his own works. In all cases where there was not especial 

 reason for the contrary, we have adopted the names given 

 to plants by those who discovered or first described them ; 

 thus we have revived the neglected name of Bartonia, 

 given to a plant by Muhlenberg, and described in 1801, in- 

 stead of adopting Centaurella of JVIichaux, which was several 

 years later ; Gi/mnopogon of P. de Beauvois has been pre- 

 ferred to Anthopngon of Nuttall, and Brasenia of Schreber 

 to Hydropdlis of Michaux. So in specific names, Frasera 

 carolinensis and Utriculnria injlata of Walter, have beea 

 used instead of F. Walteri and U. ctratophylla of Michaux. 



The most important changes of this kind have been intro- 

 duced in the Gkamine^, a family which has been less attended 

 to by our botanists than any other of the phanerogamia. 

 Mr. Nuttall has exhibited his usual acuteness in reforming 

 their characters, but, as thfe Agrostographia of P. de Beau- 

 vois had not reached this country when he published his 

 valuable work, most of his new genera must give place 

 to those of the French botanist. It is principally to this 

 work, and to the recent Agrostographia of Trinius, that the 

 author is indebted for the improved generic characters of 

 the grasses, as well as for the somewhat new arrangement 

 which he proposes. 



The Umbellifeu* are adopted with but Httle alteration 

 from Sprengel, as they are elaborated by him in the 6th vo- 

 lume of Roemer & Schultes' Systema Vegetabilium, though 

 his distribution of the North-American species of this tribe is 

 not ahogether satisfactory. 



Of the Cryptogamia, it is concluded at this time to* de- 



