11 



Poisonous Principle. 



The poisonous principle, as has been already stated, is called cicu- 

 toxin. This substance is found principally in the tuberous under- 

 ground parts of the plant, i. e., in the rootstock and in the tuberous 

 roots. When the little green shoots first come up in the spring they 

 contain considerable amounts and are almost as poisonous as the tubers. 

 Later only very small amounts are present in the lower part of the 

 stem and in the lower leaf stalks. The chemistry of cicutoxin is fully 

 discussed by Dr. C. A. Jacobson in Bulletin No. 81 of this Station. 



Time of Year When Most Dangerous. 



The early spring while the leaves are still poisonous is the time when 

 the plant is the most dangerous. At this time also the tubers may be 

 trampled or pulled out of the ground and eaten; but later they 

 develop fibrous roots and are so anchored by these and by the roots of 

 other plants, that it is almost impossible for grazing animals to pull 

 them. In the early spring in some soils the tubers are loosened and 

 often stand partly above the surface of the ground, heaved up by 

 winter frost and ice. The first leaves grow rapidly because they are 

 nourished by food stored in the tuber ; they make tempting feed before 

 other plants have made much growth (see frontispiece and Figure 6). 



Purpose of the Experimental Feedings. 



At the time when our feeding tests were undertaken, although the 

 plant had long been considered poisonous, only a few experiments had 

 been made to determine exactly what parts of the plant are poisonous 

 and how much of each part it will take to make an animal sick or to 

 cause death. Moreover, different experimenters had obtained very 

 different results. 



Because of this lack of exact information the Nevada Station has 

 made a long series of experimental feedings of various parts of the 

 plant to sheep, cattle, and horses. The old tubers were fed at different 

 times during the growing season; the new tubers, when they had 

 formed in midsummer; the leaves, when they first appeared in the 

 spring, while the older tops were fed at different times during the 

 summer. As all of the Nevada material was collected near Reno, and 

 because it seemed possible that differences of climate and soil might 

 make a difference in the poisonous quality of the plant, a few other 

 feedings were made with material which was collected in Nebraska. 

 The results of all of these feedings follow. 



TABLE No. I 



POISON PARSNIP (WATER HEMLOCK). FRESHLY GATHERED OLD TUBERS 



FED TO SHEEP 



