SILVA OF NORTH AMERICA. RHAMNACES. 
38 
shoots in axillary umbellate cymes on slender pubescent peduncles varying from half an inch to nearly 
an inch in length! The pedicels are slender, pubescent, a quarter of an inch to almost an inch long, 
and four or five times longer than the calyx, which is narrowly campanulate with more or less spreading 
acuminate lobes. The petals are minute, ovate, and deeply emarginate at the apex, and enfold the 
short stamens whose filaments are somewhat thickened at the base. The style is crowned with a slender 
two to three-lobed stigma. The fruit is globose or broadly obovoid, a third to half an inch in diameter, 
and very slightly or not at all lobed, with thin rather juicy pulp and two or three nutlets. It is at first 
green, then red, and finally black at maturity. The nutlets are obovate, usually a third of an inch 
long, rounded on the back, and flattened on the inner surface by mutual pressure, with two bony tooth- 
like enlargements at the base, one on each side of the large scar of the hilum, and a thin gray or pale 
yellow-green shell. The testa of the seed is thin and papery, its outer surface of a yellow-brown color, 
and its inner surface, like the cotyledons, bright orange-colored.’ 
Rhannus Purshiana is widely and very generally distributed from the region surrounding Puget 
Sound southward into Lower California; it extends eastward along the mountain ranges of northern 
Washington to the Bitter Root range in Idaho and the shores of Flat Head Lake in Montana. It 
occasionally occurs on the eastern slopes of the Sierra Nevada Mountains and reappears on the moun- 
In one of its forms it is scattered through the mountainous 
Rhamnus Purshiana 
tains of Colorado and western Texas. 
portions of southern California, Arizona, New Mexico, and northern Mexico. 
is a shade-loving plant. In northern California and in the region west of the Cascade Mountains 
in Washington and Oregon, where it attains its greatest size, it is usually found along the bottoms 
and the sides of canons, growing under the shelter of coniferous forests. Farther south in California 
it occurs on cool northern hillsides about the margins of the forest, or in sheltered ravines where it 
receives the protection of other trees and shrubs, and where it occasionally assumes the size and habit 
of a small tree. In the immediate neighborhood of the California coast, where Rhamnus Purshiana 
sometimes rises only to the height of a few inches, with prostrate stems forming broad cushions of 
scanty foliage, and in the Sierra Nevada at elevations of more than two thousand feet above the sea- 
level, as in the region south and east of these mountains, it occupies more exposed situations, and does 
not assume the habit of a tree.° 
The wood of Rhamnus Purshiana is light, soft or hard, and not strong. 
thin medullary rays, and broad bands of open ducts marking the layers of annual growth. It is brown 
It contains numerous 
1 In some parts of California near the coast the flowers of Rham- 
nus Purshiana, like those of many species of Frangula, continue to 
appear during the growing season, which lasts until the advent of 
frost, and it is not uncommon to find expanding flower-buds and 
The fruit is red for 
only a short time, deepening gradually in color until it becomes 
ripe fruit on the branch of a single season. 
black. The first crop, the only one in regions of scanty rainfall, 
ripens usually in September and October. 
2 Extreme forms of the black-fruited Rhamnus of western 
America are easily distinguished, although they are connected by 
so many intermediate forms that it does not seem practicable to 
characterize them specifically, or even to find satisfactory varietal 
characters for them, except in the case of the plant of the Mexican- 
boundary region. The differences consist in the shape, size, and 
texture of the leaves, and not in the more essential characters of 
flower and fruit, which do not vary in any important respect in the 
innumerable forms this plant assumes under the influence of widely 
dissimilar climatic surroundings. In the humid atmosphere of the 
northwest-coast region and of the northern Rocky Mountains, where 
Rhamnus Purshiana grows in the dense shade of coniferous forests, 
it becomes a tree with slightly pubescent bright red or green 
branchlets, and large thin broadly elliptical obtuse or abruptly 
pointed deciduous leaves, rounded or sometimes even cordate at 
the base, and somewhat hairy on the upper surface and on the prin- 
cipal veins below, with short pubescent petioles and prominent 
veins. In the less humid climate of central California the leaves 
are semipersistent, usually thicker and smaller, and often lan- 
ceolate and acuminate. The pubescence increases as humidity 
decreases, the principal veins are less prominent, and their reticu- 
lation is more conspicuous. In central California, however, indi- 
viduals occur in favored localities with the large thin leaves of the 
Washington and Oregon plant, while near them will be found 
others with the narrow coriaceous leaves of the more common Cal- 
ifornia form. On the western slope of the Sierra Nevada Moun- 
tains the plants are shrubby, with slender virgate branchlets often 
covered with bright red bark (R. rubra, Greene, Pittonia, i. 68), 
and rather thin narrow leaves. This extreme form passes on the 
one hand into the broad-leaved form of the north, and on the other 
into that of the California-coast region. In the dry climate of the 
region north and south of the Mexican boundary the branchlets and 
under surface of the leaves are densely coated with short fine pale 
tomentum. 
8 Rhamnus Purshiana is also known in some parts of the country 
as Bitter Bark, Shittim-wood, Wahoo, and Bearwood. 
