STOCK-POISOXIXG PLANTS OF THE EAXGE 



59 



THE NIGHTSHADE OR POTATO FAMILY (SOLANACEAE) 



The nightshade family contains many plants poisonous to stock, 

 the best known perhaps being the jimson weed. Datura stramonium, 

 an introduced plant which has made itself at home in the United 

 States, especially in the South. However, the only plants of this 

 family which have caused trouble, under range conditions, are the 

 wild tobaccos, Nicoticma trigo?iophyIIa, found in southern Nevada, 

 Utah, Colorado, and Mexico, and east to central Texas, and N, atten- 

 uata, found from Washington to Mexico and east to central Colorado; 

 they have been shown to be poisonous to cattle, sheep, and horses, 

 and N. trigonophylla is known to have caused considerable losses of 

 cattle and sheep in Xew Mexico. The plants cause the typical symp- 

 toms of nicotine poison- 

 ing, cattle and horses 

 being more susceptible 

 than sheep. While pre- 

 sumably the tobaccos 

 are distasteful to graz- 

 ing animals, when other 

 they 

 eat considerable 

 quantities, enough to 

 cause sickness or death. 

 N. attenuata (pi. 42). 

 plants are easily recog- 

 nized by their resem- 

 blance in form and 

 odor to cultivated to- 

 bacco. They ordinarily 

 grow in small, thick 

 patches, and under such 

 conditions can readily 

 be destroyed, as they are annuals and only need to be cut down before 

 the seeds are formed. 



forage is scarce 

 may 



Figure 27. — A horse poisoned by the horsetail milkweed. 

 Asclepias galioides. The violent convulsions are 

 characteristic of poisoning by the whorled milkweeds 



THE ASTER FAMILY (ASTERACEAE) 



COCKLEBUR (SPECIES OF XANTHIUM) 



The cocklebur or clotbur (fig. 28), is represented by a number of 

 species (Xantkiuni spp.), is very widely distributed, and has been 

 the cause of losses of cattle and swine in many localities, especially 

 in Oklahoma, Texas, and Xew Mexico. While long supposed to be 

 poisonous, it is only very recently that definite, experimental proof 

 of its toxic character has been obtained. 



It is said that the burs produce mechanical injury by irritating the 

 alimentary canal or by becoming matted together to form balls which 

 cause intestinal obstruction. It is claimed that there have been cases 

 of the lodging of burs in the throat. Some recent author- have 

 stated that the only injury produced by cockleburs is the mechanical 

 effect. There is now, however, positive proof of the poisoning of 

 swine, sheep, cattle, and chickens. There are reports also of the 

 poisoning of horses. All the poisoning is by the young plant in the 



