POISONOUS ACTION OF LOCO-WEED 85 



THE POISONOUS ACTION OF LOCO-WEED 

 AND LADIES' SLIPPER. 



The ranges of Astragalus moUisimus and Aragalus 

 lamherti general known as "loco-weed," include several of 

 the more important stock-raising districts of the west. In 

 some regions both species were known to be extremely harm- 

 ful to grazing animals, while in other places no damage 

 resulted from its consumption by cattle and horses. In all 

 of the earlier investigations of the chemical properties of 

 these plants water extracts failed to show any toxic principles, 

 and hence the reports of the poisonous action of loco by 

 ranchers were more or less discredited. Recently, however, 

 Mr. A. C. Crawford of the Bureau of Plant Industry has 

 found that a toxic principle is present, that it can not be 

 extracted by water, but is readily obtained by the use of solu- 

 tions of the animal digestive ferments. 



Furthermore it was found that this toxic principle could 

 only be obtained from plants grown on soils containing 

 barium, and hence it is reasoned that the poisonous action 

 is in reality due to barium compounds, the effects of which 

 are closely simulated. 



The author of this note found that the leaves and 

 stems of three species of Crypripedinm (C. SpcctabUe Salisb., 

 C. piihescens R. Br., and C. parviflorinn Salisb.) were 

 strongly irritant to the skin of a large proportion of the 

 persons by whom the test was made, confirming various re- 

 ports that had been made of the matter earlier. An analysis 

 of this action resulted in the localization of the poisonous 

 action in a secretion produced by the large glandular hairs. 

 (Minn. Bot. Stud. 1:32. 1894 and 2:450. 1895.) The 

 publication of these results was followed by many reports 

 of similar experiences, the most recent of which is that of 

 O. E. Jennings with the large yellow ladies' slipper in 

 Pennsylvania, and also the pink ladies' slipper, as described 

 in the Plant World for August, 1907. 



