28 BULLETIiSr 365, U, S. DEPARTMENT OF AGEICULTUEE. 



As a result of the study of the stem structure of 30 species of 

 Delphinium and 2 species of Aconitum it has been found possible^ 

 by an examination of cross sections of the stems, to distinguish be- 

 tween Delphinium and Aconitum and between six groups of species 

 in the genus Delphinium. This has been put to practical use 

 in the examination of the contents of the rumen of poisoned cattle, 

 by which means it has been possible to determine whether the animal 

 had eaten Delphinium, and to which group of species the plant 

 eaten belonged. 



PART II.— EXPERIMENTAL WORK. 



THE STATION AT MOUNT CARBON, COLO. 



The station for the detailed study of larkspur poisoning was 

 located four miles north of Mount Carbon village, in Gunnison 

 County, Colo. (PI. A^I, fig. 1). Through cooperation with the Forest 

 Service, a ranger's station, including a cabin, barn, corrals, and 

 pastures, was jorovided for the experunental work. This station was 

 in the Ohio Creek A'^alley at an elevation of about 9,000 feet, in a 

 region where Delphinium harbeyi and Delphinium men^iesii were 

 extremely abundant. In this region, also, losses which are attributed 

 to larkspur occur every year to a greater or less extent, and in some 

 years the losses have been very heavy. This station was selected, too, 

 because it was a favorable location from which studies could be made 

 upon a number of other plants supjDosed to be poisonous. It was in- 

 tended, however, that the principal experimental work should be 

 upon these two species of larkspur. The station was equipped with 

 the necessary laboratory facilities, and arrangements were made for 

 cattle and horses for experunental purposes, the work being in- 

 augurated on June 10, 1909, and continuing through that summer 

 until October 1. In 1910 and 1911 it was resumed about the middle 

 of May, and continued until nearly the 1st of October. During 

 these seasons experimental work was conducted upon cattle, horses, 

 and sheep". Acknowledgment should be made to the Forest Service 

 not only for the assistance rendered by equipj^ing the station, but for 

 the continual help of the officers of the Service during the progress 

 of the experimental work. It is desired also to acknowledge the 

 assistance rendered by the stockmen who had cattle upon the Castle 

 Creek and Anthracite ranges. Through the courtesy of these men a 

 large number of cattle were loaned for the experimental work, and 

 thus much material assistance was rendered. Wliile the experimental 

 work was going on the force kept in close touch with the men con- 

 trolling the cattle upon the ranges, and one or more members of the 

 station force accompanied the stockmen during the time the cattle 

 were driven from the Castle Creek range to the Anthracite range, 



