FOREST-TREES OF THE UNITED STATES. 5 



accompanying catalogue enumerates about 400 species, the greater por- 

 tion of which are represented by specimens in the collection. 



Some portions of the country have been so incompletely explored that 

 our knowledge of their vegetation is imperfect; yet it is probable that 

 this catalogue presents, with great accuracy, our present knowledge of 

 the trees of the United States. In two or three instances only, foreign 

 species have been admitted, because of their extensive naturalization in 

 wome sections. 



The two largest genera of trees are the oaks and the pines, of which 

 we have about 30 species of each. Of coniferous trees, including the 

 Pines, Firs, Cedars, Larches, Cypress, Sequoias, &c., we have about 60 

 species. The Rose family, including the Plums, Cherries, Thorns, &c., is 

 represented by over 30 species. Of the order Leguminoscc, or trees of the 

 pod- bearing family, we have over 20, embracing the Locusts, Acacias, 

 Redbuds, Mesquits, &c. Of ericaceous trees we have 8 species, includ- 

 ing the Califoruian Manzanita and Madrone trees, the Sorrel tree of the 

 Southern States, and others. Of Maples we have 8; of Magnolias, 7; of 

 Ash, 11; of Elms, 6; of Walnuts and Hickorys, 13; of Poplars, 8; and 

 of Birch, 6 species. 



The usual difficulty has been encountered of deciding as to the stand- 

 ing of certain forms which some botanists regard as species and others 

 as only varieties. In most well-marked cases, these are entered in the 

 catalogue under distinct numbers, either as species or as varieties, as the 

 evidences in the case seemed most convincing. 



The range, or botanical region, of each species is indicated in a general 

 manner, thus: Those trees which occur more or less extensively over the 

 whole or the larger portion of the country east of the base of the Rocky 

 Mountains or east of the Mississippi River are marked Eastern United 

 States. This region is subdivided, by a line running eastward from the 

 mouth of the Ohio River to the Atlantic, into two portions, one of which 

 is called Northeastern United States, and the other Southeastern United 

 States. Other localities are indicated as Southern States, New England 

 States, Western States, Alleghany Mountains, &c. The western portion 

 of the United States and Territories is marked in detached regions, as 

 follows: Rocky Mountains of Colorado, or Rocky Mountains of Colorado 

 and Utah; Sierra Nevada Mountains of California, Oregon, and Wash- 

 ington Territory ; California; Southern California ; Arizona. The por- 

 tion of the country adjoining the Mexican border is indicated by the 

 locality Western Texas and westward. 



Certain portions of our country have not yet been sufficiently explored 

 to determine accurately all the species of trees thereto belonging, This 

 is the case with respect to the southern portion of Florida. Some spe- 

 cies which at one time were thought to be indigenous in that region 

 have not been confirmed by any late investigations, and will probably 

 have to be erased from our list. The same difficulty occurs with respect 

 to some of the trees of the Rocky Mountains and the western coast, par- 

 ticularly the Conifers and the Willows. 



In the short time allotted to making this collection, it has not been 

 possible to obtain wood specimens of every species given in the catalogue. 

 The number wanting, however, is but a small percentage of the whole. 



Among the good results growing out of this work, we may mention, 

 first, that much information has been gained respecting species hitherto 

 imperfectly known ; and, secondly, that four or five new species, or species 

 before unknown to our flora, have been obtained. These are mainly in 

 South Florida, and include two exogens, viz, an Anona or Custard 



