38 



Geographical Botany of the United States* 



United States forms no exception to the observation which applies 

 to other parts of the globe, viz : that in approaching the tropics the 

 vegetable forms become not only more rich in their colouring, and 

 more luxuriant in their growth, but also that the number of the spe- 

 cies is greatly increased. To confirm what has just been said, I 

 need only repeat, that Mr. Elliott, in his Flora of South Carolina 

 and Georgia, enumerates as found in these two states alone, about 

 300 more Phenogamous plants, than belong to all the Northern 

 and Middle States. It may also be added, that of 619 genera, 

 described by Elliott as belonging to South Carolina and Georgia, 

 132 are not found in the Flora of the Northern States ; and that of 

 592 genera enumerated in Torrey's Compendium, 73 are not found 

 in the work of Elliott, though some of these occur in Virginia., 



Proceeding to the North, the species just cited as characteristics 

 of the Southern vegetation, gradually disappear ; and as we reach 

 yirginia, we meet with other forms indicative of a more northern re- 

 gion. This may be said to be the neutral ground between the north 

 and the south, and does not assume the decided character of either. 



As we reach Pennsylvania, New-Jersey, and New- York, a change 

 in the aspect of the forests is observable. The Pinus rigida, L. 

 (pitch pine,) Pinus strobus, L. (white pine,) Pinus canadensis, L+ 

 (hemlock spruce,) which in the south are confined to the mountain- 

 ous ranges, and then stinted in their growth, rise to their nati ve height 

 on the lowlands. The same may be said of the Pinus alba, Jliton, 

 (white spruce,) Pinus nigra, Aiton, (black spruce,) and Pinus mi- 

 crocarpa, Lamb. P. pendula, (red and black larch.) Here, on the 

 banks of streams, in marshes and elsewhere, are the Thuja occiden- 

 talis, L. (white cedar,) Betula papyracea, Mich. B. populifolia, 

 Aiton, (white birch,) Betula lenta, L. (black birch,) and Betula ez- 

 celsa, Aiton, (yellow birch,) which, if found at all in the Southern 

 States, are confined to the Alleghanies. Of the smaller trees, the 

 Willows are also peculiar in this respect. Of from 40 to 50 species, 

 at present known as belonging to the United States, not more than 

 six are found much south of Pennsylvania ; and Mr. Elliott remarks, 

 that the Salix nigra, L. (black willow,) is the only species which is 

 found in the low country cf Carolina, except the exotic, 8. babyk- 

 nica, and the S. vitettina, which are occasionally cultivated in gar- 

 dens. Among other plants, peculiar to the Northern Atlantic re- 

 gion, may be named Xylostcum ciliatum, Pursh, DierviUa cana- 

 densis, Rhodora canadensis; several species of Ribes, Celastrus, 



