26 



hungry animals will. Further, poor half -starved animals are more 

 easily and readily poisoned than when well fed. Thus the condition 

 of the animal determines in a large measure the extent to which it will 

 graze poisonous plants and the probability of serious or fatal poisoning. 



THE SHOWY-LEAVED MILKWEED AND OTHERS AS 

 POISONOUS PLANTS 



After two years of observation in the field and in the feeding corrals 

 we have good reason to believe that the narrow-leaved milkweed is of 

 far greater importance as a poisonous plant than any other species of 

 milkweed growing in Nevada. For that reason only a few experiments 

 with the other milkweeds have been made at this Station. The follow- 

 ing discussion of the other species found in Nevada will give a general 

 idea of their appearance and poisonous properties : 



The Showy Milkweed (Asclepias speciosa). 



This species of milkweed can be found in many parts of Nevada, but 

 it does not seem to be very abundant anywhere. It requires about the 

 same conditions for growth as does the narrow-leaved milkweed, and 

 they are often found growing together. 



Live stock do not like it, and it is eaten only under stress of hunger. 

 Often fields grazed by cattle may' be closely cropped, with this milk- 

 weed standing untouched. 



As a poisonous plant it seems to be much less important than, the 

 narrow-leaved milkweed. Figure 4 shows the general appearance of 

 this plant growing in the field. 



Feeding experiments were made with (1) the green leaves, (2) the 

 leaves as they had dried up naturally in the field, (3) the seeds, and 

 (4) the pods. 



TABLE X 



The Showy-Leaved Milkweed Green Leaves, Pods, Seeds, and Dried Leaves 



Fed to Sheep 



The above feedings seem to show that ( 1 ) the green leaves are poison- 

 ous, (2) relatively large amounts are required to cause poisonous symp- 

 toms in a mature range ewe, (3) the pods alone are poisonous, (4) the 

 seeds are highly poisonous, and (5) the plant dried naturally in the 

 field contains little of its original poisonous matter. 



Lambs have been fatally poisoned by grazing upon the tender growth 



