84 BULLETIN 365, U. S. DEPARTMENT OF AGRICULTURE. 
in Farmers' Bulletin No. 720, Prevention of Losses of Live Stock 
from Plant Poisoning. 
After the plant has matured, as has been shown elsewhere, its 
toxicity diminishes, and cattle, finding at the same time an abun- 
dance of other more attractive feed, eat very much less of the larkspur 
so that the danger of poisoning is very slight, and in the fall, after 
the plant begins to dry, cattle may and do eat it in large quantities 
with impunity. 
It is generally considered by stockmen that poisoning is more 
likely to occur immediately after a rain, or even when the plants are 
wet with dew. There seems to be no reasonable explanation of the 
supposed fact of the greater toxicity of the plant when wet. It 
seems possible, however, when cattle are feeding hastily in a larkspur 
area after a rain, that rather than thrust their heads and faces into 
the wet grass they may eat more of the higher plants; in this way 
they would consume more of the larkspur and consequently become 
poisoned. Cattle, too, in the time of a storm gather together in the 
valleys and under trees where larkspur is very abundant, and doubt- 
less eat more of it on this account. 
Probably, also, when cattle are handled upon a supposed poisonous 
area it would aid somewhat in preventing loss if pains were taken 
to make sure that none of them were constipated. This probably 
could be accomplished, where cattle are watered at specific places, 
by the use of a small amount of magnesium sulphate or sodium 
sulphate in the drinking water. 
GENERAL SUMMARY. 
1. The larkspurs from very ancient times have been recognized as 
poisonous plants, but complaints of stock poisoning by these plants 
have been confined almost entirely to the mountain ranges of western 
North America, where heavy losses have been reported, especially 
among cattle. 
2. It is rarely possible to recognize macroscopically larkspur ma- 
terial in the stomach contents of cattle. By means of microscopic 
sections of stems, however, not only can Delphinium be distinguished 
from other plants but groups of the genus can be distinguished from 
each other. The genus falls into six different types of stem struc- 
ture. 
3. Experimental feeding of larkspur was carried on for three 
seasons at Mount Carbon, in Gunnison County, Colo. In this work 
four species of Delphinium were used which have been identified as 
Delphinium barbei/i, D. menziesii^ D. andersonii, and D. robustum. 
A large number of animals were used in this work, including horses, 
cattle, and sheep. Similar feeding experiments were conducted 
