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a political limit, has always been made a conventional line between 
the northern and southern floras of the States east of the Mis- 
sissippi river, or the temperate region of eastern North America. 
Although contiguous, the mountains of North Carolina and 
Virginia are of two very different types, and any one accustomed 
to collecting in the wilderness of the western portions of the former 
State is immediately struck with the great topographical differ- 
ence between the two regions. In the tract of country under 
consideration the mountain ridges and valleys are usually long, 
although much varying in length, and run in nearly parallel lines, 
whereas in North Carolina, in place of the parallel system, there 
is a mass of short ridges and peaks thrown together in all con- 
ceivable positions and at every possible angle and relation to one 
another. As can naturally be inferred, there is considerable dis- 
similarity in the floras of the two tracts. The conventional line 
between the two states is by no means absolute, and there is 
much overlapping and intergrading of their respective floras. 
This was especially observed, and it furnished many facts con- 
cerning the geographical distribution of species. 
The two factors that have exerted the greatest influence in 
producing such an extensive flora as there exists are the varied 
character of the contour of the region and the variety of the 
geological formations of its valleys and its mountain ranges, 
which latter are the Blue Ridge, the Alleghanies and the Cumber- 
land Mountains. As to the former, there are all conditions of 
erosion and varying altitudes ranging from the valleys, some of 
which are 2,000 feet above the level of the sea, to ridges 
5,000 feet and peaks nearly 6,000 feet in height. The latter fac- 
tor's influence can readily be understood when we consider both 
the restricted and extensive limestone valleys followed by thick 
strata of the different sedimentary rocks on thé mountain slopes 
and ending with the granite or gneiss of the higher peaks, each 
formation supporting a greater or less number of peculiar species 
and varieties. In addition to these there are two other factors, 
the climatic and meteorological conditions as they prevail there. 
They may not exert as much power in enlarging the flora as in 
rendering it as luxuriant as it is. The temperature seems to be 
just about the requisite degree, seldom so hot as to produce exces- 
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