POISONOUS AND INJURIOUS PLANTS 89 
poisonous to all classes of livestock and humans. Symptoms of lucky- 
nut poisoning include vomiting, cold clammy skin, sunken eyes, and 
convulsions, followed by death. Fortunately, all parts of the plant 
are very unpalatable and not likely to be eaten. Humans, especially 
children, should be warned against eating parts of the plant out of 
curiosity. 
MANAGEMENT AND Controt.—The scarcity of plants and their oc- 
currence in inaccessible places lessens the chances of livestock poison- 
ing and reduces the control measures necessary. Livestock do not 
browse on luckynut ordinarily; however, animals should be denied 
access to the plants. Undesired plants may be either grubbed out or 
killed with selective herbicides provided surrounding plants are not 
endangered by their use. 
PLANTS THAT CAUSE MECHANICAL INJURY 
Some plants common to the Virgin Islands are hazardous to live- 
stock because they can cause external or internal mechanical in- 
juries. These plants usually possess sharp awns, burs, spines, or 
thorns, which may cause injury by tearing the flesh, especially around 
the eyes and mouth, cripple animals by working into their hoofs, 
or produce ulcers or compactions in the digestive tract. Some of 
these plants are poisonous also. 
The spines on the fruit of burgrass (Cenchrus echinatus L.) mahoe 
(Triumfetta semitriloba Jacq.), and on the stems and fruits of nickers 
(Caesalpinia spp.) render these plants dangerous. Stinging nettle 
(Tragia volubilis L..) and cowage (Stizolobium pruriens (Stickm.) 
Medic.) vines may cause serious skin irritations to browsing animals, 
especially around the mouth parts. Other common pasture weeds that 
cause injury by becoming lodged in the hoofs or other body parts of 
grazing animals include casha (Acacia spp.) ; so-called century plants 
(Agave spp.) and (Yucca spp.) ; fleshy, attractive ornamental spurges 
of the genus Ewphorbia: all of the cactaceous plants; and pingwing 
(Bromelia pinguin L.). 
Hairballs of plant origin are caused by the massing together of 
plant hairs or fibers in the stomachs or intestines of animals to form 
intestinal blocks which may eventually result in death. Three-awn 
grass (Aristida adscensionis 1.) and bedgrass (Sporobolus spp.) are 
known to cause such compactions. The spines on the fruits of bur- 
grass and mahoe may cause ulcers in the digestive tracts of animals. 
The leaves of elephant-ear (A/ocasia macrorhiza (1.) Schott) con- 
tain crystals that are harmful to the mouth parts and tongue of 
browsing animals. Plants that cause mechanical injury to livestock 
are listed on page 90. 
Many of these plants are also harmful toman. For example, plants 
that have the contact poisons of (A) stinging hairs such as stinging 
nettle and (B) irritating acrid sap or juice such as the spurges should 
be avoided where possible. Serious injury may result from getting 
thorns or spines into the hands, feet, or other body parts. 
