28 BULLETIN 365, U. S. DEPARTMENT OF AGRICULTURE. 
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. (PL VII, fig. 1) . Through cooperation with the Forest 
Service, a ranger's station, including a cabin, barn, corrals, and 
pastures, was provided for the experimental work. This station was 
in the Ohio Creek Valley at an elevation of about 9,000 feet, in a 
region where Delphinium barbeyi and Delphinium menziesii 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 supposed 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 experimental 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 equipping 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. While 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, 
