176 MISC. PUBLICATION 101, U. S. DEPT. OF AGRICULTURE 
are regarded as a potential source of supply for the drug santonin 
(740); it would appear, therefore, that they should have value in 
eliminating intestinal worms from livestock and game animals. 
Alkali sagebrush (A. natronensis) is a species typical of moist to 
wet shores of alkaline lakes and ponds in eastern Idaho, Wyoming, 
and adjacent Colorade. It is one of the important winter sheep- 
browse plants in southeastern Idaho. Some authorities hold it to 
be a form of A. longifolia. 
Stiff sagebrush (A. rigida) is a low bush found on scab lands and 
other rocky, mountainous sites in the Northwest. The woody twigs, 
with their clusters of linear or linearly dissected leaves, simulate 
somewhat, save for their silvery silky sheen, a spray of pinon or 
some other short and rigid needled pine. In some places this is a 
valuable winter browse plant, and ordinarily it is accounted fair 
sheep forage; it is of especial interest because of a predilection of 
horses for it (47). : 
Threetip sagebrush (A. ¢ripartita) occurs from Washington to 
California, Colorado, and Montana. It is a much-branched, silvery- 
white, fine-leaved shrub, 6 to 48 inches high, and is typical of sunny 
open park areas, and of sandy gravelly rocky soils, between about 
5,000 and 8,000 feet, frequently being an associate of bitterbrush 
and wild-ryes. In some areas, notably portions of southern Idaho, 
it is the most abundant species of sagebrush. It is practically 
worthless as summer browse but is fair sheep feed in very early 
spring and again in fall, especially after frost; it is of most value 
when it occurs on winter range. 
Wright sagebrush (A. wrightii, syn. A. bakevi) is a species of the 
woodland and yellow pine zones of southern Colorado, New Mexico, 
and eastern Arizona. In Arizona it is usually held to be poor 
forage save in early spring, when it assumes considerable local 
importance. In northern New Mexico and contiguous Colorado 
it is commonly held to be fairly good spring and fall browse for 
sheep and goats and fairly good or good winter horse and cattle 
feed. 
Groundsel Tribe (Senecioneae) 
GROUNDSELS (SENECIO SPP.) 
Some of the woody groundsels are limitedly browsed; such are 
S. longilobus (syn. S. filifolius) and S. spartioides of the Southwest 
and Middle West. The palatability of these undershrubs is, how- 
ever, low, especially as compared with some of the herbaceous species 
of this genus. 
HORSEBRUSHES (TETRADYMIA SPP.) 
Tetradymia is a group of low, rigid, hoary, sometimes spiny 
shrubs inhabiting dry sites. The genus is confined to the Western 
States, consists of about nine species and two subspecies, or varieties, 
and is chiefly represented in the Great Basin region. Under normal 
grazing conditions the palatability of horsebrushes is usually nil 
or else very low except, perhaps, on desert, winter and early spring 
range. 
Littleleaf horsebrush (TVetradymia glabrata) is a small-leaved, 
rather slender-branched shrub, known also as greasewood and spring 
rabbit brush, 1 to 4 feet high, ranging on dry hills and plains from 
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