COMPOSITAE THISTLE FAMILY ARNICA 795 



Distribution. Higher altitudes of the Rocky Mountains, from Colorado to 

 California and British Columbia. 



Arnica mollis Less. Hook. 



A leafy branching perennial, tomentose or villous-pubescent or nearly 

 smooth; leaves denticulate or dentate, acute or obtuse; lower leaves tapering 

 into a margined petiole, upper broader at the base and clasping; flowers much 

 smaller than the preceding; ray flowers yellow; achenes hirsute-pubescent. 



Arnica monocephala Olin. 



An erect, simple, branching perennial, from 1-2 feet high; leaves opposite; 

 long peduncled heads; leaves narrow, oblong and lanceolate, the upper linear; 

 ray flowers, yellow. 



Distribution. Grows in woods and moist localities, Montana to New Mex- 

 ico and westward. 



Poisonous properties. This well-known arnica has, for some time, been sus- 

 pected of being poisonous. When bruised all the plants exhale the odor of 

 arnica. Chesnut and Wilcox state : 



It has an odor and taste much like that of the official drug, and, in fact, an extract 

 made from the heads is considerably used locally as a liniment. No specific cases of pois- 

 oning caused by the plant have been reported from Montana, and we are not aware that it 

 is eaten, but it has, nevertheless, been suspected of being poisonous to stock. 



Dr. S. B. Nelson states that a sheep ate 2 pounds (of the leaves?) of A. alpina within 

 a day without experiencing any bad effect. The plants had been gathered eighteen hours. 



25. Senecio (Tourn.) L. Groundsel 



Perennial or annual herbs; shrubs or trees; leaves alternate; heads many 

 flowered, solitary, corymbose or paniculate; involucre cylindrical or bell shaped; 

 principal bracts in one series, distinct or united at the base, usually with some 

 shorter rays, outer ones pistillate or none; disk flowers perfect; corolla tubular; 

 achenes terete or those of the marginal flowers compressed; 5-10 ribbed; pappus 

 of numerous capillary bristles. A large genus of 1000 species of wide distribu- 

 tion. Some ornamental. Some species have been looked upon as poisonous. 



Dr. Day, in the Twenty-third Annual Report of the Bureau of Animal In- 

 dustry, 1906, gives the following in regard to a disease supposed to be asso- 

 ciated with a species of this genus : 



At the present stage of the work there appears reason for associating this malady with 

 an affection of cattle known in Nova Scotia as Pictou disease, with Winton disease of horses 

 of New Zealand, and with Molteno cattle disease of South Africa. The tissues examined 

 present practically the same lesions as those described for the above-mentioned affections 

 namely, interlobular connective tissue hyperplasia, fatty infiltration of the liver cells, and 

 hemorrhages into the spleen. 



Pictou disease, Winton disease, and Molteno cattle disease have been investigated time 

 and again in an endeavor to find a causative agent. All inoculation experiments have failed, 

 and it has only been found of late that feeding experiments with certain weeds have given 

 seemingly reliable results. 



Pictou disease, occurring in Pictou and Antigonish counties, Nova Scotia, is now 

 ascribed to the ingestion of a weed called ragwort. Winton disease is thought to be caused 

 by a member of the ragwort family, Senecio Jacobaea. The Molteno disease of South 

 Africa is probably induced, according to recent investigations, by still another ragwort, 

 Senecio Burchelli. At least these weeds when fed to animals in their respective localities 

 have produced diseases followed by a train of symptoms corresponding to those seen in the 

 naturally induced disease. The post-mortem findings were also quite similar. It was also 

 proved that these plants were most dangerous in the young state. Yet another variety 

 known as Senecio latifolius was found to be deadly to stock. 



In some parts of the states in the west Senecios are common but they are not 



