IMPORTANT WESTERN BROWSE PLANTS 67 
The browse value of several of the native western plums and “ wild 
cherries” on sheep and cattle range is considerable, perhaps 
especially so on sheep allotments and in late summer and fall. The 
species, however, do not as a rule resist overgrazing well. Livestock 
are most apt to take the season’s twigs, and repeated cropping of 
this sort so rapidly devitalizes the bushes that sheep and goat killed 
cherry and plum thickets are not an uncommon sight wherever there 
has been overstocking or other mismanagement. The plum char- 
acteristic of stooling out from the base or by root suckers is con- 
ducive under too close utilization to sapping the vitality of the root 
system. 
The cherries, chokecherries, and laurel-cherries, or cherry-laurels, 
have a more or less well-marked tendency (doubtless associated with 
the often pronounced almondlike odor of the herbage) to develop 
hydrocyanic (prussic) acid (HCN), involving the poisoning of 
livestock (16, 17, 19, 44, 53, 68, 76, 77, 81, 95). Long points out 
that Schrader, as long ago as 1803, made a chemical study of cherry- 
laurel poisoning. The statement is frequently made that cherry 
leaves are poisonous only when in a wilted condition, and that they 
are practically innocuous when fresh, but experiments have demon- 
strated that this is largely a fallacy. Howard (90) has found, in 
the case of the eastern chokecherries that the largest, most tender, 
and most succulent leaves develop the greatest amount of hydro- 
eyanic acid and that the dry, woody leaves of mature plants yield 
so little as to render them nearly harmless. He considers, there- 
fore, the greatest danger to be from the vigorous, succulent leaves 
of young shoots (which cattle and sheep are probably most lable 
to eat). Such leaves when wilted are also poisonous and even 
_ when dried are still to be regarded with suspicion. Fortunately the 
most virulent part of the plant, the seed pit, is not eaten by live- 
stock or, if swallowed with the harmless fleshy part of the fruit, 
passes unassimilated out of the digestive tract. 
Despite the numerous notes in literature there is still much to be 
learned about the details of western chokecherry and cherry-laurel 
poisoning, such as the quantity of leafage (for various species) nec- 
essary for a lethal dose, and the time or times of greatest danger. 
It is evidently the part of safety not to graze cherry patches too 
early or at other times when young, vigorous shoots and leaves 
are much in evidence, not to drive sheep when hungry along trails 
extensively lined with these species, nor to permit livestock to gorge 
themselves on cherry alone without a liberal admixture of other 
feed. | 
- Birds, as well as rodents and some other mammals, exhibit a 
marked fondness for the fruits of the native species of Prunus and 
are largely responsible for the dissemination of these plants, which 
are, therefore, species of importance in the study of indigenous wild 
life and its conservation. 
Black chokecherry (Prunus melanocarpa, syns. Cerasus demissa 
melanocarpa, Padus melanocarpa, Prunus demissa melanocarpa), 
known locally as cherry, chokecherry, and (black) western choke- 
cherry (131), is a shrub (or small tree mostly shrubby and branch- 
ing at or near the base) varying when fully grown trom about 20 
inches to a known but very unusual height of 30 feet. The spheri- 
