32 
§ II. Fruit not dated; the margin opaque. 
THIN LEAVED ALDER. 
ALNUS tenuifolta; foliis lato-ovatis subacutis duplicato- 
crenatis glabris basi rotundatis longe petiolatis, stipulis 
deciduis, pedunculis fcemineis duplicato-ramosis. 
This very distinct species of Alder which arranges 
with our common species, (A. sen-data ,) was met with 
on the borders of small streams within the range of the 
Rocky Mountains, and afterwards in the vallies of the 
Blue Mountains of Oregon, a chain which may be called, 
as it were, in comparison of their elevation, the Alle- 
ghanies of the West. 
This species falls short of the character of a tree, but 
yet it is scarcely inferior in size with our common spe- 
cies, growing to about the height of a man, with nume- 
rous short branches, covered with a smooth grey bark. 
The leaves are about 2 inches long by li wide, with 
slender petioles, from a half to f of an inch in length; 
they are of a thin consistence, and usually smooth, with 
obtuse denticulations. The fruiting branches are often 
subdivided, each branch bearing from 3 to 5 small 
roundish ovate aments, of which the scales are very 
distinctly lobed. The fruit is unusually small and ellip- 
tic, terminated by the 2 remaining styles, and having a 
thin opaque margin. 
Plate X. 
A branch of the natural size. a. The fruit. 
