IMPORTANT WESTERN BROWSE PLANTS 97 
mainly in the pifon, oak-brush, and covillea belts; it is grazed—some- 
times extensively so—by cattle and other livestock, though its 
average palatability is probably not over fair. 
Littleleaf sumac (2. microphylla, syn. Rhoeidium microphyllum), 
occurring on dry, “desert ” foothills from western Texas to southern 
Arizona and south into Mexico, is a common, spreading edible- 
fruited bush of characteristic aspect; it occurs usually in scattered 
stand and its palatability appears to be very low. 
Evergreen sumac (/?. virens, syn. ? R. choriophylla), which 
ranges from western Texas to southern Arizona and south into 
Mexico, is reported by Bray (12) to be a pioneer in the vegetation 
of limestone ledges in west Texas, forming a protection for other 
species which occupy more slowly the difficult situations. It thus 
has a local, conservative influence with regard to water supply and 
erosion. 
POISON IVIES AND POISON OAKS (TOXICODENDRON SPP.) 
Closely related to the sumacs and sweet-sumacs (Rhus spp.), and 
united with them by some botanists, are the poison oaks, poison 
ivies, and poison sumacs (Zowxicodendron spp.), whose juices are very 
poisonous to the skin of most persons. While more data on this 
subject are needed, animals as a rule seem not to be affected by this 
plant, though dogs sometimes have their eyes swollen from nosing 
around the bushes. There are two western species. 
Poison oak (7. diversilobum, syn. R. diversiloba) ranges from 
Washington to California and is said to be the most widely dis- 
tributed shrub in California. It ranks as slight to fair cattle feed. 
Western poison ivy (7. rydbergii, syn. R. rydbergii) occurs from 
British Columbia to South Dakota, western Oklahoma, Arizona, and 
Idaho. It is sometimes grazed by livestock but, on the whole, is 
nearly worthless. 
STAFF TREE FAMILY (CELASTRACEAE) 
To the staff tree family in the West belong four woody genera, in 
addition to Pachistima, represented by 11 species of shrubs, small 
trees, or woody vines, all apparently without palatability to livestock. 
American bittersweet (Celastrus scandens) is an eastern woody 
climber which gets as far west as Montana and New Mexico and has 
bitter herbage. 
Western wahoo (Luonymus occidentalis) and eastern wahoo (£. 
atropurpureus), both known as burningbush, are the better known 
of the three species of Euonymus (spelled by some Evonymus), 
ernamental shrubs and small trees occurring natively in the West. 
The western species ranges from Washington to western Nevada and 
California, and the eastern reaches Montana. 
Greasebush (Morsellesia spinescens), known also as greasebrush, 
is the best known and most widely distributed of the four species 
of Forsellesia (syn. Glossopetalon). It occurs from Washington 
to California, Chihuahua, Oklahoma, and Colorado, mainly in dry, 
rocky sites at low elevations. Greasebush is of interest to the ecolo- 
gist as a pioneer species, able to establish itself in solid granite rock. 
21259°—31——7 
