Statistics of the Flora of the Northern States. 



205 



nous plants now comprised in the volume,* and mark the true 

 division eastward between our southern and our northern bo- 

 tanical regions, namely, at the northern limit of the Live Oak, 

 the Long-leaved Pine, and the Black Moss (Tillandsia usneoides) 7 

 which grows pendent from their boughs. 



On the Mississippi, the plant most southern in character which 

 crosses the parallel is Jussicea repens. This sparingly extends up 

 the Ohio to lat. 38°, where also the Taxodium reaches about as 

 far north as on the Atlantic coast. 



In the elevated region through which the middle of our 

 southern boundary passes, great numbers of northern plants are 

 of course found to extend much farther southward. 



Our western boundary, the Mississippi Eiver, while it takes in 

 a considerable prairie-region, excludes nearly all the plants pe- 

 culiar to the wide western woodless plains, which stretch from 

 the Saskatchewan to Texas and New Mexico, and approach our 

 borders in Minnesota and Iowa. A list of the plants which we 

 may be said to have derived from this region, will be given here- 

 after. 



The northern boundary, being that between the United States 

 and British America, varies through about five degrees of lati- 

 tude, and nearly embraces Canada proper on the east and on the 



* It would apparently exclude from the flora of the Northern States the follow- 

 ing species : — 



Gordonia Lasianthus. Benzoin melisseefolium. 



Stuartia Virginica. Tetranthera geniculata. 



Zanthoxylum Carolinianum. Stillingia sylvatica. 



Berchemia volubilis. Quercus virens. 



Viburnum obovatum. " cinerea. 



Mitreola petiolata. Sagittaria falcata. 



Liatris odoratissima. Burmannia biflora. 



" paniculata. Tillandsia usneoides. 



Sericocarpus tortifolius. Smilax Walteri. 



Chrysopns gossypina. " lanceolata. 



Baccharis glomeruliflora. Zygadenus glaberrimus. 



Kalmia birsuta. Mayaca Michauxii. 



Ilex Cassine. Paepalanthus flavidus. 



" myrtifolia. Laehnocaulon Michauxii. 



" Dahoon. Vilfa Virginica. 



Gelsemium sempervirens. Ctenium Americanum, 



Forsteronia difformis. Uniola paniculata. 



Olea Americana. Paspalum distichum. 



Fraxinus platycarpa. " Digitaria. 



Probably a good many more southern species inhabit this corner of Virginia, of 

 which I have as yet no indications. There is little doubt that the long-leaved Pine 

 crosses the line, and perhaps an arborescent Yucca grows on the sea-shore. — Of char- 

 acteristically southern trees that have found their way still farther northward on the 

 coast, even beyond Virginia, I can only mentiun two, namely, the Red Bay (Persea 

 Carolinensis) and the Bald Cypress {Taxodium distichum), both found in Delaware, a 

 little beyond lat. 38° 30'. Two other characteristic trees, viz., the Palmetto and 

 Magnolia grandifiora, stop about as far short of our line as the two former pass be- 

 yond it. 



