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 
some 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 Leguminose, 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 Californian 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 givenin 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 beep 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 
