Poisonous plants
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Read about Poisonous plants in the Standard Cyclopedia of Horticulture
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The first group includes those plants which are mainly harmful to farm cattle, causing serious troubles which may result eventually in the death of the animal. This group includes such plants as the crimson clover, Trifolium incarnatum, spiny cacti (Opuntia), the hairs and spines of which form the hair-and spine-balls known as phyto-bezoars. The branched hairs of the calyx of the crimson clover, if eaten by horses and cattle, when in full flower, are rolled together to form the hair- balls which have been responsible for the death of many animals. The spines of species of Opuntia in Mexico and the southwestern United States cause the laceration of the mouth and tongue of cattle and death has resulted in a number of cases, where these spines have been rolled into phyto-bezoars. AEgagropilae are balls formed from animal hairs which have been licked off and swallowed. Through the peristaltic movement of the intestines these have been rolled into balls. The silex in the stems of the scouring-rushes (Equisetum) is responsible for inflammation of the digestive organs of cattle. The hygrometrie structures attached to the fruits of such grasses as Stipa capillata (Russia), S. spartea (United States), Aristida hygrometrica (Queensland), and Heteropogon contortus (New Caledonia), by their spiral movements cause the pointed ends of the fruits to bore into the skin and flesh of animals in those regions of the earth. The blue-mold, Aspergillus fumigatus, which lives at blood temperature, penetrates the lung tissues of calves and pigeons, and its masses of spores fill up the air-cavities and lung-passages, causing asphyxiation. These are some of the illustrations of plants that kill, or cause injury, by mechanical means. The poisonous plants, however, are those that contain some chemical poison which either produces irritation, disease, or death by its direct action. The season of the year has a direct influence on the activity of a poisonous plant. Melter (1899) records that his horse ate 500 pounds of the dried hay of Passiflora incarnata in August without injury, while in March, eight months later, 25 pounds of the hay of this plant killed another horse. The condition or age of the plant is important. The poisonous principle in the spotted hemlock, Conium maculatum, is volatile, and hence the dried plant is less poisonous than the fresh. The leaves of wild black cherry, Prunus serotina, are more poisonous when dry than when fresh, owing to the development of hydrocyanic acid. Some parts of a plant are more poisonous than others. For example, the seeds of the Jamestown weed, Datura Stramonium, are more deadly than the remainder of the plant. Again it may be said that the relative amounts of poisonous substance vary in different individuals of the same species and that small doses of some poisons are taken with beneficial results, for instance the use in medicine of belladonna, strychnine, and aconite. The toxic properties of plants are not due in all cases to the same chemical substance. It is well known that several plants contain a number of toxic bodies. For example, the green hellebore, Veratrum viride, contains the alkaloids jervin, cevadin, and veratrin. Sometimes the same poison is present in more than one species, as solanin in the tomato and the potato. Not all animals are equally affected by the same poison, as for example, the darnel which poisons men, dogs, horses, and sheep, but is innocuous to cows, pigs, and ducks. Some persons are susceptible to poison ivy, others are not. This susceptibilty may be increased by sickness, or a rundown condition. Some animals acquire a craving for certain injurious plants, as for example, the loco weeds of the United States, stemless loco weed, Oxytropis Lambertii, and in Australia, according to Maiden, the indigo plant, Swainsona galegifolia. Kobert divides poisonous plants into three groups: (1) irritants which cause gross anatomic changes, as croton-oil; (2) blood poisons, as ricin; (3) poisons which kill without anatomic changes, as morphin, digitalin, and the like; and a fourth class may be added, (4) skin-irritants, as poison ivy. The most poisonous lower plants are fungi belonging to the genus Amanita. The two most virulent are the toadstools, Amanita muscaria, which contains muscarin, and A. phalloides with phallin. Fortunately, an antidote has been discovered for the first in the administration of hypodermic injections of atropin beginning with 1-100 of a grain, and increasing the dose to a strength of 1-60 of a grain. For phallin, no antidote is known. Of the higher plants, the most noted poisonous ones are: Aconitum Napellus (monkshood) ; Delphinium Geyeri (larkspur); Oxytropis Lambería and Astragalus mol- lissimus (loco weeds); Rhua radicans (poison ivy), which is a serious skin-irritant; Khus vernix (poison sumac), which is also decidedly toxic to the skin; Cicuta maculata (cowbane), which contains two poisons conin and cicutoxin; Conium maculatum, the classic poisonous plant, from which came the death-draught of the philosopher Socrates; Kalmia latifolia and A". angustifolia, the two poisonous laurels; Datura Stramonium (Jamestown weed); Atropa Belladonna (deadly nightshade) and others too numerous to mention. Popular interest usually attaches to the poison ivy, Rhus radicans or R. Toxicodendron (Fig. 3088), a root- climbing vine with temate leaves, and the poison sumac, Rhus vernix (Fig. 3089), with pinnate leaves. Both of these plants have white fruits and hence are easily distinguished from the non-poisonous sumacs. The poison ivy is everywhere in the eastern states along roads, fence-rows and uncultivated ground, while the poison sumac grows in swamps and is less common. Both are skin-irritants, causing what physicians call dermatitis. If the susceptible person thinks he has come into contact with the plants, he should wash his hands and face with alcohol, as this dissolves and removes the non-volatile oil, toxicodendrol. Smoke from a brushwood fire containing these plants is toxic, and so is the Japanese lacquer made from the inspissated juice of a sumac, Rhus vernicifera. Unfortunately, all parts of these plants are virulent and at all seasons of the year. One of the best remedies is an alcoholic solution of sugar of lead, and the extract of grindelia (sold at drug-stores) is sometimes used. Local remedies are fresh bean leaves, stems of touch-me-not (Impatiens) and plantain leaves (Plantago lanceolate). At least, these leaves allay the burning sensation of the inflamed skin. An authoritative work on toxic plants is the "Manual of Poisonous Plants," by L. H. Pammel, professor of botany in Iowa State College of Agriculture, in two parts, Part I (1910) and Part II (1911) with a total of 977 pages. Other publications have been issued. Two plants much in prominence at the present tune in Wyoming on account of their poisonous effect on livestock are discussed by H. G. Knight, as follows: "Woody aster, Xylorrhiza Parryi (Fig. 3090), is found throughout the state of Wyoming, but is confined to certain districts characterized by a gumbo clay soil, more or less intermixed with gravel and containing more or less of alkali and other salts. This plant probably causes greater losses among sheep in the state of Wyoming than all other poisonous plants together, but may be easily recognized by those familiar with the range. So far as is known, sheep are the only species of range animal susceptible to poisoning by woody aster. No antidote is known and there is much question whether a satisfactory antidote will be obtained as the action of the poison is powerful and death comes speedily with many pathological changes." Pammel writes, "Death camas, Zygadenus intermedius, is a near relative of the better known Zygadenus venenosus. In Wyoming the most common species is the Z. intermedius and the greatest losses noted have occurred in early spring when the plant is in bloom, and before early forage is plentiful. The plant grows on the sandy plain as well as in the drier and stonier foothills. It has been found that the poisonous properties are due to the presence of alkaloids, one of which at least is new to science. An antidote has not as yet been determined." John W. Harshberger. CH
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References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
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