NOTE. 
In the annexed descriptions of genera and species, care has 
been taken to select such plants as may be most easily obtained 
for purposes of analysis: for this reason most of the common 
exotics have been admitted ; as flowers from the garden may 
often be at hand, when circumstances would render the collec- 
tion of wild plants inconvenient. 
BOTANICAL DISTRICTS. 
Eaton considers North America as divided into two botanical 
districts, northern and southern. The dividing line to be drawn 
from the mouth of Delaware river, (N. Lat. 39°, W. Lon. 75°,) 
to the south end of Lake Michigan, (N. Lat. 41° 31) ; leaving 
in the northern district all Pennsylvania, and the north part of 
Delaware, Maryland and Ohio. The division line thus rises as 
we go towards the west, because southern plants extend to high- 
er latitudes on the western side of the Allegany range, than on 
the eastern side. 
The northern district is divided into eastern and western, by 
a line drawn from the intersection of the Allegany range and 
the Potomac river, in the direction of Cayuga lake. The Alle- 
gany mountain is the dividing line in the southern district. 
Explanation of figures, letters and characters, used in the Gen- 
eric and Specific descriptions. 
NUMBERS. 
The first number following the generic description, is the 
number of the natural order of Linnaeus, to which the genus 
belongs: the second number is that of Jussieu. The first num- 
ber on the left of the generic name, is the number of the artifi- 
cial class to which it belongs ; the second, of the artificial order; 
the first on the right, is the number of the natural order of 
Linnaeus ; the second , of Jussieu. 
LETTERS. 
E and If' are used to denote that the plant is found in the 
eastern or western division of either of the districts. 
<$, at the end of a description, shows that the plant grows in 
the southern as well as northern district. 
