20 BULLETIN 575, U. S. DEPARTMENT OF AGRICULTURE. 



however, that this treatment does not bring about a real cure. It is 

 important that herders should recognize the plant and so far as pos- 

 sible avoid ranges or parts of ranges where it is especially abundant. 

 Generally speaking, when a band of sheep is found to be suffering 

 from this plant it is because they have been eating it for some time, 

 and perhaps a single large f eeding may have precipitated the trouble, 

 which is mainly due to the accumulated effect of prolonged feeding. 



OAK. 



Throughout the grazing regions of the West there is a very general 

 belief in the poisonous properties of oak leaves, more particularly in 

 regard to their supposed toxic properties for cattle. It is quite 

 generally thought that poisonous effects are produced in the spring 

 when cattle are eating the buds and young leaves. This belief 

 applies especially to the Gambel oak (Quercus gambeUii), which is a 

 common scrub oak of Colorado, Utah, and New Mexico, and to the 

 shinnery oak (Quercus Tiavardi), a low shrub in eastern New Mexico 

 and western Texas. Extended experiments are being carried out 

 upon these plants by the U. S. Department of Agriculture. These 

 experiments are still in progress, and the results can not be considered 

 as definitely conclusive. It seems probable, however, that oak 

 leaves do not have any distinctly poisonous properties, but, on the 

 contrary, especially when the leaves are mature, form a valuable 

 element in the forage of range animals. When cattle are fed exclu- 

 sively on oak leaves they suffer from constipation, so that on an 

 overgrazed range this condition may become so serious as to pro- 

 duce illness and death. No serious results need be expected, how- 

 ever, provided the forage is sufficiently abundant so that there is 

 enough variety to preclude the exclusive use of oak. 



PSORALEA TENUIFOLIA. 



This is a very common plant on the plains of Colorado, Wyoming, 

 and Montana, and is found as far east as Illinois. There have been 

 many reports of its poisonous effects on horses and cattle, and it is 

 said to have been used hj the Indians for poisoning fish. Several 

 species of Psoralea have been examined by chemists, and have been 

 found to contain poisonous principles. One of the species has been 

 popularly known as a loco weed. There has been no experimental 

 work to prove its effect on domestic animals, and as it is distasteful 

 to grazing animals it can not, under any circumstances, be considered 

 an important poisonous plant. There is good reason, however, to 

 suspect it of sometimes being harmful, if animals are forced to eat 

 it by reason of poor pasturage or because it is present in large quan- 

 tity in hay. Plate XXX is a picture of this plant. 



