FORESTS AND TREES OF NORTH AMERICA. 247 



their name (abbreviated) in small capitals in the last column. The 

 character (?) prefixed to a locality indicates doubt whether this or 

 some allied species is really the one attributed to that place. 



Future information may lead to the addition to the general lists of 

 some trees included in the lists of trees nearly peculiar to Florida 

 and Mexico, or to the contrary change. The numbers and letters 

 prefixed to the names are intended to refer to charts of the distribu- 

 tion of trees, now in course of preparation. As trees do not form a 

 natural series distinct from other plants, and as size does not serve 

 as a criterion for their separation from shrubs, it might be considered 

 more scientific to have included all looody plants in this catalogue ; 

 but as that would have swelled the list entirely beyond bounds, I 

 have made a selection, guided first by the size, and secondly by utility, 

 independent of size. It may be advisable in future to add to or to 

 omit some of the species. Thus, as to the grape vines, Prunus 

 maritima and Cerasus pumila, I included these and a few more woody 

 plants, not properly trees, for various reasons. Some of the vines 

 grow a foot in diameter, and are of use for wood as well as fruit. 

 The others are interesting as analogues of trees, growing under 

 peculiar circumstances. They may, too, become worth cultivation 

 for fruit ; and one of my objects was to include all such as far as pos- 

 sible. The species of Crataegus and Pr?w?is mostly come under this 

 exception. 



The reason for giving the maximum heights is, that it is thought 

 the cultwation of trees will become some day a matter of national 

 interest, and I wish to show what they are under the best natural 

 circumstances, supposing that, with cultivation, they will at least 

 equal this standard. Some of the western plants are little more than, 

 shrubs ; _ but as the western regions are comparatively poor in trees, 

 I have stretched the limit a little there, since shrubs become more 

 valuable where trees diminish in number. 



Nearly all the varieties mentioned by various authors are given ; 

 because, first, the difterence between a species and a permanent variety 

 is scarcely definable ; second, because they are often as truly charac- 

 teristic of botanical regions as the species themselves. In this article 

 Popuhis canadensis is separated from P. monili/era for example, 

 because Micliaux could not identity the latter east of the Mississippi ; 

 and we look upon it as belonging rather to the Rocky Mountain than 

 to the Apalachian province. 



As Michaux notices a diflference in the beeches of Canada and the 

 more southern United States, we preferred (as in the other supposed 

 varieties) to consider them as species having distinct ranges, until 

 enough good specimens can be procured to determine the fact. It is 

 doubtful whether there are any trees extending entirely across the 

 continent, within the limits of the United States, which are not more 

 properly included among those of the Lacustrian or Mexican provinces. 



Collections of the leaves, fruits, bark, and wood of our native trees 

 are particularly desirable, and from as many localities as possible, in 

 order to determine both their range and abundance, and also to decide 

 those knotty points as to true specific distinctions, which still perplex 



