18 BULLETIN 1245, U. S. DEPAETMEXT OF AGRICULTURE. 
lower levels. The two plants intermingle to seme extent, but after a 
little experience one is able to distinguish between them, as there 
are certain noticeable differences in the leaA^es. Oxytropis besseyi is 
known in Montana sometimes as the red loco, because of the color 
of the flowers. Although the plant is closely related to the white 
loco and grows in the same regions, there is abundant experimental 
evidence that it is harmless. It should not be considered as a loco 
plant. The writer considers that the term " loco " should be applied 
only to such leguminous plants as have been proved to have poison- 
ous properties. 
Purple Loco (Astragalus mollissimus). 
Astragalus molUssimus, popularly known as purple loco, woolly 
loco, and sometimes as Texas loco, is a plant that has been histori- 
cally known as the true loco. It is probably the first plant which was 
recognized as a loco dangerous to livestock. It does not grow north 
of Nebraska, and perhaps is most abundant in the Panhandle of 
Texas, although it is found in adjoining regions of New Mexico, 
Colorado, Kansas, and in Nebraska. The leaflets are very hairy and 
are much broader than those of the white loco. The plant also has a 
true stem, while the white loco has sometimes been known as the 
" stemless loco." 
Plate XVIII shows a very small plant of this loco. The flowers are 
not so conspicuous as in the white loco, and the corolla is of a deep- 
purple color. The pods are shorter, thicker, and of a deep-brown 
color. Large plants of purple loco may under favorable circum- 
stances be about a foot in height and perhaps 2 feet in diameter. It 
does not commonly grow in the great abundance characteristic of 
the white loco, but there are sometimes fairly extensive fields. Where 
it grows in connection with the white loco the purple loco is more 
inclined to grow in depressions, while the white loco is found more 
abundantly at slightly higher levels. Purple loco is particularly 
destructive to horses; cattle may be poisoned by it, too, although this 
is rarely the case, perhaps because cattle do not eat it very readily. 
Blue Loco (Astragalus dipiiysus). 
Plate XX is a picture of Astragalus diphysits, known as blue loco, 
which is a type of a number of loco plants growing in the South- 
west. These plants differ in their appearance very markedly from 
the white and purple locoes. The leaflets are small and of a deep- 
green color like alfalfa. 
Closely allied to the plant illustrated are a number of species 
which there is every reason to consider as true loco plants and which 
it is incumbent upon stockmen to prevent stock from eating. 
In past years the blue loco has been known mainly as a horse-pois- 
oning plant, and has been responsible for heavy losses in Arizona. 
However, it will affect also cattle and sheep, and recently has caused 
much trouble with cattle. 
Astkacaius NOTOXTS. 
This loco, shown in Plate XXI. is a low. spreading plant which 
grows in considerable abundance in southern Arizona. It is thought 
