Colorado Plants Injurious to Livestock 
57 
example, prickly lettuce, sow thistle, and prickly poppy all have a milky 
juice, yet are not true milkweeds. The three above-mentioned have 
alternate leaves, while the true milkweeds have opposite leaves. 
There are many species of true milkweeds within our borders. 
All are herbs, with opposite leaves (rarely alternate), or sometimes 
several at a joint on the stem. The leaves and stems are often some¬ 
what woolly, sometimes smooth. The flowers are in umbels, pink, 
purplish, or white in color, and peculiar in shape. The fruit is a pod 
which splits open at maturity allowing numerous seeds to come ouc, 
each of which has a silky tuft of hairs at the end. 
The most common milkweed in our section is the showy milkweed 
(Asclepias speciosa) (fig. 8o). It is perennial 2 to 5 feet high with 
large, opposite leaves, and purplish flowers in spherical, terminal clus¬ 
ters. It grows in good, rather moist soil on plains and in foothills 
throughout the state. 
The low milkweed (Asclepias pmnila) (fig. 81) is 2 to 15 inches 
tall, and grows from a woody root. The leaves are very narrow and 
crowded on the stem. The pods are long, slender and much smaller 
than those in the preceding species. It prefers dry, sandy soil. It is 
most common at low altitudes. 
The whorled milkweed (Asclepias verticillata) (fig. 82) is a leafy 
plant, I to 2 ^ feet high. The long, narrow leaves are several at a 
joint oif the stem. It grows on dry plains. 
There are several so-called green milkweeds in Colorado, the chief 
one being the green-flowered green milkweed (Acerates viridiflora). 
It is a plains plant. 
Poisoning by milkweeds. —Many of these plants have an acrid 
juice. The showy milkweed is said to b' poisonous. It con¬ 
tains asclepion. Another species (A. verticillata) grows extensively 
along river bottoms and native meadows of Colorado, and is suspected 
of being posonous. At Olathe several cattle died with symptoms oif 
poisoning that had eaten hay containing considerable quantities of this 
weed. A sack of the plants was sent to the Experiment Station for 
examination. Rabbits refused to eat it and watery and alcoholic ex¬ 
tracts were tried, but the chances are that the animals in this instance 
died from some other cause. While many of the milkweeds are pois¬ 
onous they are for the most part rejected by animals. 
BLACK NIGHTSHADE, STUBBLE-BERRY (Solanum nigrum) 
An annual low, spreading plant (fig. 83.) with oval leaves. The 
white flowers are in small drooping groups along the side of the stem. 
They are of the potato type: 5-parted calyx, 5-parted corolla, 5 stamens. 
The berries are black, smlooth and spherical. The plant is introduced 
from Europe and assumes weed habits with us. It occurs at low alti¬ 
tudes in the states, it is not abundant, however. 
THREE-FLOWERED NIGHTSHADE, WILD TOMATO (Sola- 
nuni triflorum) 
A low, spreading annual (fig. 84) with deeply cut leaves. The 
flowers are usually arranged in groups of three, on nodding stalks. 
