124 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



a closely related species of Oxytropis are generally charged with the 

 trouble in question. 



Dr. Rotbrock (in Wheeler's. Report) says: 



The term loco, simply meaning foolish, is applied because of the peculiar form of 

 dementia induced in the animals that are in the habit of eating the plant. Whether 

 the animals (horses chiefly) begin to eat the plant from necessity (which is not likely) 

 or from choice I am unable to say. Certain it is, however, that once commenced, 

 they continue it, passing through temporary intoxication to a complete nervous and 

 muscular wreck iu the later stages, when it has developed into a fully marked dis- 

 ease, which terminates in death from starvation or inability to digest more nourish- 

 ing food. The animal toward the last becomes stupid or wild, or even vicious, or 

 again acting as though attacked with "blind staggers." 



Several analyses have been made of the plants which are said to be 

 the cause of this affection, but without satisfactorily ascertaining what 

 is the peculiar poisonous principle. No antidote has been discovered. 

 If the plants can be ascertained and exterminated, the trouble should 

 come to an end ; but, even if the plants are recognized, their extermina- 

 tion over large tracts of country will be difficult and expensive. 



We append descriptions and figures of the two plants which, in Colo- 

 rado and New Mexico, have been most frequently charged with the 

 noxious effects. 



Astragalus mollissimus — Loco Weed. 



A perennial herbaceous plant of the region of the great plains from 

 Colorado to New Mexico, Texas, and Arkansas. It belongs to the order 

 Leguminosce or pea family. There are usually a great many stalks pro- 

 ceeding from a large strong root-stock. They are reclining toward the 

 base and erect above. These stalks are so short that the leaves and 

 flower-stalks seem to proceed directly from the root. They are branch- 

 ing at the base and give rise to numerous leaves and long stems bearing 

 the flowers and pods. The leaves are usually from 6 to 10 inches long, 

 composed of 9 to 15 leaflets (in pairs except the upper one). These 

 leaflets are of oval form, J to § of an inch long, of a shining, silvery hue, 

 from being clothed with soft, silky hairs. The flower-stalks are about 

 as long, or sometimes longer than the leaves, naked below, and at the 

 upper part (J to J) bearing a rather thick spike of flowers, which are 

 nearly 1 inch long, uarrow, and somewhat cylindrical, the corolla of a 

 velvet or purple "color, the calyx half as long as the corolla and softly 

 pubescent. The flower has the general structure of the pea family, 

 and is succeeded by short, oblong, thickish pods, J to f inch long, very 

 smooth and with about two seeds in each. 



This is said to be less common than the next plant described {Oxytro- 

 pis). Plate I. 



Oxytropis Lambertii — Loco Weed. 



A plant belonging to the same family as the Astragalus mollissimus. 

 It is about the same height, and like it grows in strongly rooted clumps, 

 but it differs in having an erect habit, with shorter leaves and longer 

 and stiffly erect flower-stalks. The leaflets are longer and narrower, 

 about 1 inch long, by \ to £ inch wide, and hairy especially on the 

 upper surface. The flower stalks proceed from the root-stock, are usually 

 9 to 12 inches long, and naked except near the top, which has a rather 

 close and thick cluster of flowers, much like those of the Astragalus in 

 general appearance, but differing in some minute characters which sep- 

 arate it into another genus, and are succeeded by erect lance oblong, 

 pointed pods, of about an inch in length. This plant is very abundant 



