IMPORTANT WESTERN BROWSE PLANTS 45 
prevail, it may be desirable to graze closely enough to make the 
plants assume a bushy and more spreading form. However, to do 
this with any class of livestock but goats will cause overgrazing of 
the herbaceous vegetation and result in erosion. Continued over- 
grazing seriously affects forage production and may even kill the 
plants. On the whole true mountain-mahogany is somewhat better 
regarded from the forage standpoint in the Southwest and the Great 
Basin than it is farther north and west. In the mountainous regions 
of southern Utah this is almost uniformly regarded as the most 
palatable and important browse for cattle, sheep, and goats. Aldous 
and Shantz (2) figure the carrying capacity of mountain-mahogany 
range, including the abundant grasses occurring with the browse, 
as 20 to 40 head of cattle per section for the period of each year 
that the lands occupied by this type can be grazed without injury 
to the vegetation. The species is one of the most valuable winter 
feeds for deer and sther herbivorous game animals. 
Pammel (96, p. 38) quotes Greshoff to the effect that the glucoside 
amygdalin, partly convertible into HCN, occurs in true mountain- 
mahogany and states that this species must be regarded as poisonous. 
However, no authentic case of poisoning due to any species of Cerco- 
carpus has ever been reported to the Forest. Service and evidences 
of this particular species’ value as browse are so abundant, uniform, 
and harmonious from all western regions that it is difficult to con- 
ceive of the species as harmful. It is probable that the quantity of 
glucoside in true mountain-mahogany is so small as to have only 
chemical rather than practical significance. 
Silver mountain-mahogany (C. argenteus) and birchleaf moun- 
tain-mahogany (CC. betulozdes, syn. C. betulaefolius), the former of 
the Southwest and the latter of California, are two species very 
closely related to C. montanus and of similar palatability. C. argen- 
teus is one of the most valuable goat browses of New Mexico and 
Arizona, usually being ranked as excellent, and it is well relished also 
by cattle and sheep. C. betulozdes is frequently abundant enough to 
be an important factor in the carrying capacity of cattle and sheep 
ranges and often attains tree size. | 
Curlleaf mountain-mahogany (C. ledifolius), frequently known 
simply as curlleaf or mountain-mahogany (3), is much the com- 
monest, most widely distributed. and best known of the narrow- 
leaved and hard-leaved species. It ranges from eastern Washington 
to California, Arizona (north of the Grand Canyon), Colorado, and 
Montana, occurring between about 2,000 and 4,500 feet in the north- 
ern and northwestern and up to 9,000 feet or perhaps even higher, 
in the southern part of its range. It is found mainly on warm 
dry rocky ridges, mostly on southern, the drier western, or (in 
its Pacific States range) on eastern slopes, but is sometimes observed 
on clayey or loamy soils. It is perhaps the largest and most typically 
treelike of the species of the genus. On winter range, or very late 
and very early in the season when other feed is scarce curlleai moun- 
tain-mahogany has slight forage value; otherwise it is ordinarily 
deemed next to worthless. The evergreen nature of the leaves 
renders them subject to yearlong utilization. Standley (/26) states 
that the Gosiute Indians of Utah used the wood of this species in 
making their bows. 
