76 SILVA OF NORTH AMERICA. BETULACES. 
shores of Kicking Horse Lake’ to the valley of the lower Fraser River in British Columbia, and 
southward through the Rocky Mountains to northern New Mexico, to the Sierra Nevada of southern 
California, and to Lower California.” In the northern interior region of the continent it is the common 
Alder by mountain streams; it is very abundant on the eastern slopes of the Cascade Mountains and 
of the California Sierras, and forms great shrubby thickets six or seven thousand feet above the sea 
along the head-waters of the rivers of southern California which flow to the Pacific Ocean ; it is the 
common Alder of eastern Washington and Oregon, Idaho and Montana, and is very abundant in 
Colorado and northern New Mexico, where it grows to its largest size, often lining the banks of streams. 
The wood, which has not been examined scientifically, is sometimes used for fuel. 
Alnus tenuifolia was first distinguished by Thomas Nuttall,? who, in 1834, found it, during his 
journey across the continent, by the banks of small streams on the Blue Mountains of Oregon. Subse- 
quently it was considered a variety of Alnus incana, the Speckled Alder of the northeastern part of 
the continent, but this differs from it in its thicker and less pointed rarely lobed leaves, pale and 
pubescent on the lower surface, its darker bark, and the conspicuous persistent white spots that cover 
its branches. 
1 Macoun, Cat. Can. Pl. 438 (Alnus incana, var. virescens). 3 See ii. 34. 
2 Brandegee, Zoé, iv. 216 (Alnus incana, var. virescens). 
g' P] ? 
EXPLANATION OF THE PLATE. 
Puate CCCCLV. ALNUs TENUIFOLIA. 
. A flowering branch, natural size. 
Scale of a staminate ament, rear view, enlarged. 
A staminate flower, enlarged. 
- Pistillate flowers with their scale, front view, enlarged. 
- A fruiting branch, natural size. 
. Scale of a strobile, enlarged. 
A nut, enlarged. 
ONAMAPR WH 
. A winter-bud, natural size. 
