STOCK-POISONING PLANTS OF THE RANGE. 
31 
RAYLESS GOLDENROD (Isocoma wrightii). 
In the Pecos Valley in New Mexico and Texas there has been for 
many years a disease of animals known as mill?: sickness, alkali 
disease, and trembles. It was noted especially in cattle, and, because 
the disease may be conveyed through the milk, not only caused losses 
by- death, but seriously interfered with the dairy business. For a 
time it was supposed to be a contagious disease, but recently it has 
been shown that it is produced by Isocoma wrightii, popularly 
known as the rayless goldenrod or jimmy weed. While the most 
serious effects of the weed in the Pecos Valley have been upon cattle, 
it will poison also horses and sheep. 
The plant is shown in Plate XLII. It is a perennial, growing 
ordinarily to a height of 2 feet, but it may reach 4 feet or more. 
It is very abundant in some localities, frequently making a thick 
hedge along ditches. 
One of the most prominent symptoms is the muscular trembling 
which has given rise to the name " trembles " as applied to the disease. 
It has been shown that 
sometimes the offspring 
are poisoned by the 
mother's milk. 
Figure 29 shows a 
sheep poisoned by ray- 
less goldenrod. This 
animal trembled vio- 
lently and could stand 
only a minute or two. 
In Figure 30 is a steer 
in the last stages, 
shortly before death. 
It is important that 
stockmen should make 
certain that their ani- 
mals get no large quan- 
tity of the plant. If 
animals are found eating it, they should be removed immediately to 
locations where there is none. In the early stages of the disease 
animals recover very quickly if put on good pasture. 
The plant is rather easily destroyed by grubbing out to a depth 
of 2 or 3 inches, and thoroughly cleared pastures remain clear for a 
long time. 
Another rayless goldenrod, /. c or onopi folia, found in southern 
Arizona, is thought to produce the same harmful effect as the- /. 
wrightii, but there has been no experimental work to confirm this 
belief. 
FERN. 
Fig. 30. 
A steer poisoned by rayless goldenrod {Iso- 
coma wrightii) ; just before death. 
The common bracken fern, Pteris aquilina, which is illustrated in 
Plate XLIII, should be mentioned here as one of the poisonous 
plants, although the losses from it are probably not large. It has 
long been known abroad that the fern is poisonous to cattle and 
horses. There have been comparatively few reports in this country 
