A very large number of plants have at various times been suspected of possessing poisonous properties and causing harm to live stock. Of these it is quite probable that many are in practice entirely harmless, but some must be included as possibly deleterious, complaints having been made which vary in gravity from a slight irritation to causing death.

Purging Flax (Linum catharticum L.). It is perhaps doubtful whether this plant is really poisonous unless taken in considerable quantity by animals—as it is quite unlikely to be. It may, however, be included here, as it is stated to contain a glucoside which is purgative and which on fermentation yields prussic acid.

Furze or Gorse (Ulex europÆus L.). In view of the fact that Gerrard isolated from the seeds of Gorse the alkaloid Ulexine, which is identical with Cytisine (p. 27) and that the alkaloid is also contained in less quantity in the bark of young shoots, this plant has been suspected of possessing toxic properties. Experiments (179)^[7] with the alkaloid definitely showed it to be a nerve and muscle poison, 3 milligrammes having killed a chloroformed cat with convulsions in three minutes, though the animal could be kept alive as long as artificial respiration was kept up. As, however, Gorse has long been used very widely and in considerable quantities as a fodder the percentage content of the alkaloid must in general be exceedingly small, and no harmful effects need be feared from the consumption of the cut and bruised plant. Possibly the seeds might prove injurious if eaten in quantity.

Melilot (Melilotus sp.) may at times cause injury. Ewart (82) writes: “All the species contain Cumarin, a volatile odoriferous principle, which in excess produces a disinclination to locomotion, paralysis and ultimately fatal symptoms. No harm is to be apprehended if the amount present does not exceed 10 per cent. of the herbage.”

Silver Weed (Potentilla Anserina L.). This well-known and elegant little weed is scarcely likely to be eaten to any extent by farm stock, though it may possibly be taken occasionally on roadsides. It has not been proved to be poisonous, but Pott states that it has a strongly constipating effect (213).

Tormentil (Potentilla Tormentilla L.). In relation to supposed bracken poisoning (see p. 87) in regard to which experiments were conducted by the Board of Agriculture and Fisheries, Tormentil occurred in several instances with the bracken in localities where this plant was reported to cause poisoning. Two feeding experiments in which the weed was fed to heifers gave negative results. In a further case, however, 4 or 5 lb. were collected from a field where sick animals were grazing, and fed to a heifer; it appeared to be the cause of rise of temperature (to 106° F.), diarrhoea, and the passing of a considerable quantity of blood in the fÆces for three days, after which the animal improved. It was, however, slaughtered, and lesions were found similar to those found in animals dying in the field from so-called bracken poisoning. Though the plant was suspected, results generally were not held to prove that it was the cause of poisoning (25). According to Van Rijn the root of Tormentil contains a considerable quantity of Chinovic acid (C₃₂H₄₈O₆?).

Wall-Pepper (Sedum acre L.) is regarded as emetic and purgative, but to lose the harmful properties on drying.

Sundews (Drosera sp.) are reputed to be poisonous to sheep, but no evidence has been found.

White-Rot or Marsh Penny-Wort (Hydrocotyle vulgaris L.) is stated to have caused inflammation of the digestive tract, and hÆmaturia; and to contain a toxic substance Vellarin (213).

Wild Parsnip (Pastinaca sativa L.). This plant has often been supposed to be poisonous, but Pammel shows that in Iowa the plant is quite harmless, as it appears to be in Britain.

Devil’s-Bit (Scabiosa succisa L.) is stated by Moir to have caused injury to cattle in one instance (Vet. Record, 1899), causing salivation, gritting of the teeth, twitching of facial muscles, and slightly protruded, abraded, swollen and sensitive tongue. An experiment on cattle showed the plant to induce violent inflammation of the mouth and tongue.

All-Heal (Valeriana officinalis L.) is not likely to be eaten by stock in sufficient quantity to cause poisonous symptoms, though it is stated to contain the poisonous Valerianic acid and Oil of Valerian. According to Chevalier (vide Henry) this plant contains an alkaloid not yet fully characterised.

Canadian Erigeron (Erigeron canadensis L.), sporadic in England, is suspected in America. It contains an oil, chiefly a terpene (C₁₀H₁₆). It has an acrid taste, causes smarting of the eyes, soreness of throat, aching of extremities, and colic; and irritation to people handling it (203).

Mayweeds (Anthemis sp.). It is not at all clear whether these plants are more than irritant in character, and they are so very common and widely distributed that there would probably be more evidence if they were poisonous. A. Cotula is regarded as suspected by Smith and Halsted, while Ewart says that it is obnoxious to stock on account of its unpleasant flavour, and if eaten by them in time of scarcity is apt to give their flesh, milk, or butter an unpleasant flavour. GÜssow states that this species blisters the mouth and nostrils of animals. In his investigations at Kew, Greshoff found that the seeds of A. Cotula and A. arvensis contain much hydrocyanic acid. (He further found that the cyanogenetic glucoside from A. aetnensis Schouw. and A. chia L. belongs to the amygdalin type, giving off hydrocyanic acid and benzaldehyde on hydrolysis. “The strong odour of benzaldehyde may even be observed on grinding the seeds with water. Species of Anthemis contained from 0·15 down to 0·03 per cent. of hydrocyanic acid.”)

Cat’s-Ear (HypochÆris radicata L.). No record of poisoning of Cat’s Ear has been found, but it may be mentioned here, since Ewart says of it: “It contains a bitter, milky sap, which makes it unpalatable though not entirely poisonous.... An exclusive diet of this weed could not help but injure stock eventually.”

Dodders (Cuscuta sp.), when parasitic on clovers and fed as fodder or hay, have been suspected of causing digestive troubles in horses and cattle in the United States. MÜller records a case of poisoning of young pigs by C. europÆa, with inflammation of the intestines and nervous symptoms. Barbey determined the presence of the glucoside Cuscutin in C. Epithymum.

Viper’s Bugloss (Echium vulgare L.) is suspected of being poisonous; according to Friedberger and FrÖhner it causes slavering (see also Cynoglossum).

Hound’s Tongue (Cynoglossum officinale L.). To what extent this plant is actually poisonous is not clear, but with some other members of the order (Echium vulgare, Anchusa officinalis), it contains the two alkaloids Consolidine and Cynoglossine—the former of which paralyses the central nervous system and the latter the peripheral nerves. (Greimer, 1900: vide Henry).

According to Hooker, Hound’s Tongue is narcotic and astringent, and Smith includes it as a simple vegetable irritant, causing nausea and purging. No records of actual poisoning of animals have been found.

Broom-rape (Orobanche minor Sutt.) has been suspected, and according to Boitel is liable to cause violent colic when it occurs in considerable proportion in clover and is ingested with it (73). On the other hand, in a case noted by Stapledon, in which Broom-rape (O. minor) had completely overrun the aftermath on a farm near Fishguard, two-year-old cattle devoured the plant with apparent relish and cleared off most of it in a few days after being turned in. The farmer stated that he saw no trace of colic or other ill effects. (Jour. Bd. Agric., September, 1916.)

Great Mullein (Verbascum Thapsus L.). Though it does not appear to be touched by farm live-stock the Great Mullein must be mentioned here. The leaves and flowers have been used medicinally as an emollient and pectoral, while the seeds possess narcotic properties and serve to stupefy fish (73). Pammel states that the plant causes irritation, but is probably not very poisonous to stock.

Toadflax (Linaria vulgaris Mill.). Cornevin describes Toadflax as acrid and poisonous, but says that stock reject it, and he could record no accidents to animals. In his full and excellent account of this weed, Kraus says it is regarded as poisonous, or suspected of being so, but that according to most accounts it is not harmful to cattle (168). Leunis regards it as suspicious on account of its acridity. Some German authorities say it is willingly eaten by cattle, but it is generally believed to be avoided, and owing to its disagreeable odour and acrid taste this view is probably correct. The plant has not been exhaustively studied, and while Smith gives the toxic principle as Oil of Snapdragon and the resin Gratiolin, it may be observed that Toadflax contains the glucoside Linarin (C₆₄H₅₆O₄₀).

Figworts (Scrophularia nodosa L. and S. aquatica L.). These plants are not likely to be eaten by animals, but Cornevin states that the former is strongly emetic and purgative, and that in excess it may cause superpurgation ending in death. MÜller says that the two species have respectively caused poisonous symptoms in a cow and a sheep; in the case of the cow there were loss of appetite and symptoms of paralysis. From S. nodosa Walz extracted a bitter, crystalline substance, Scrophularine.

Yellow Rattle (Rhinanthus Crista-galli L.). When grass land is put under the plough Yellow Rattle present may re-appear in a cereal crop as a semi-parasite, and its seeds may later be ground up with the grain, imparting a reddish or violet-brown colour and an unpleasant taste to the flour and even bread made from it. It is strongly suspected of being poisonous, like Pedicularis and Melampyrum, but it is by no means clear how far it may prove harmful to stock. It is believed by some people to impart a bad taste to the butter made from the milk of cows grazing on infested pastures. Lehmann ate without harm 35 grammes (about 1¼ oz.) of the seeds made into a cake and cooked; and during four days he gave a rabbit 1238 grammes (2·7 lb.) of the fresh plant with half-ripe seeds, without apparent injury (73).

In some poor pastures it occurs in excessive quantity, and would appear to be only very slightly poisonous, or would have attracted wider attention. It is possibly only poisonous after being eaten for a prolonged period, as in the case of Lolium temulentum, and Lathyrus sativus. The seeds contain the bitter-sweet glucoside Rhinanthin (C₂₉H₅₂O₂₀), which is suspected of having poisonous properties.

Cow-Wheat (Melampyrum arvense L.). It seems clear that Cow-Wheat is at least not poisonous unless eaten in very considerable quantities—amounts in fact which in practice are most unlikely to be eaten. The seeds may occur in cereal grains, and hence be ground up into meal. As they are said to contain a glucoside analogous to Rhinanthin, have a bitter taste and peculiar odour, and impart a violet coloration to flour, their presence in cornfields is most undesirable. According to Pammel this plant induces sleepiness and colic.

Ground Ivy (Nepeta Glechoma Benth.) is, according to Schaffner, poisonous to horses. It contains a volatile oil and bitter principle, as also does Catmint (N. Cataria). In a case which came before the Board of Agriculture and Fisheries in 1906 three horses became ill with symptoms of poisoning, and the only weed found in the lucerne they were getting was Ground Ivy, and this was suspected but not proved to be the cause. In a further case, reported in 1909, eleven horses were believed to have been poisoned by this weed, and in one of the dead horses scarcely any food but Ground Ivy was found, and to it the veterinary surgeon in attendance attributed death. During preceding years several horses had died in the locality (Ely), owing, it was believed, to poisoning by the same weed. The losses, however, were not proved to be due to this plant.

In the Veterinary Journal (October, 1914, p. 515) poisoning of horses by this weed was noted (after Ferenczhazsy in the Recueil de MÉdecine VÉtÉrinaire). The author observed nine cases of intoxication due to the weed, though it is stated that it “has occasioned no trouble in cattle and sheep that consumed it.” The symptoms in horses were “anxious look, dyspnoea, salivation, sweating, dilatation of the pupils, cyanosis, signs of pulmonary oedema.” Two horses died. In 1913 similar cases were observed by other owners, and terminated fatally.

Hooker states that N. Glechoma is “bitter and aromatic, formerly used for beer, occasionally for tea.”

Orache (Atriplex sp.). So far as known these plants are not poisonous, but it may be stated that Greshoff found the seeds of five species, and the leaves of two species, to contain a Saponin.

Nettles (Urtica sp.). Nettles are not generally regarded as poisonous otherwise than as causing painful nettle rash on the bare skin, but Urtica dioica L. is stated to have caused the death of dogs (Berliner TierÄrztliche Wochenschrift, 1909).

Yellow Flag (Iris Pseud-acorus L.). The wild Flag was noted by LinnÆus as dangerous to cattle, but no case of actual poisoning has been found in the literature. The plant is stated to have marked emetic and purgative properties, and Cornevin remarks that in Belgium intense gastro-enteritis is attributed to it. It contains the glucoside Iridin (C₂₄H₂₆O₁₃).

Narcissus sp. Various Narcissi (e.g. N. pseudo-narcissus, N. poeticus, and others) have been regarded as irritant to the hands. They would rarely if ever be eaten by live-stock in Britain, but it is stated that on the Continent many poisonings of cattle, goats, and pigs have been recorded, not infrequently ending in death after two or three days. The Narcissi are strongly narcotic, emetic, and purgative, and cause dilated pupils. Pott states that they cause inflammation of the digestive tract, and convulsions, sometimes with fatal results; and according to Pammel N. poeticus induces intense gastro-enteritis. N. pseudo-narcissus contains the alkaloid Narcissine (C₁₆H₁₇O₄N), which with cats causes nausea and purgation (Henry).

Common Fritillary (Fritillaria Meleagris L.). The Fritillary or Snake’s Head occurs only in a few places in England, and truly wild perhaps only rarely in southern and eastern counties—not in Scotland or Ireland. No definite case of poisoning has been found in the literature, but the plant is stated to be poisonous. It contains the bitter alkaloid Imperialine (C₃₅H₆₀NO₄), which is a heart poison.

Bog Asphodel (Narthecium ossifragum Huds.) has by some been regarded as a poisonous plant, and MÜller says that the poisoning of cows has been recorded, and also that a cat died after drinking the milk of an affected cow. The toxic property is believed to be the glucoside Narthecin.

Molinia caerulea, Moench. A short account by Pott shows that when forming the principal part of moorland pasture grasses, and hence extensively eaten, this grass causes brittleness of the bones of stock, and in sheep chlorosis and wool eating. It also induces hÆmaturia, but if free from parasitic fungi (e.g. Claviceps microcephala) and not covered with microscopic, sharp crystals, is quite harmless if only eaten as a secondary or incidental fodder. This grass seems to be very poor in lime (Immendorf, 1898), and Schulze and Castoro found the internodes of the stem to contain a considerable quantity of a pentosan (Xylan). It is poor in nutritive constituents. The harm done is due perhaps in part to this fact, and in part to more or less accidental or occasional constituents (as 0·046 per cent. of lead oxide in a case of the var. altissima near some lead works). Plants said to be occasionally similarly harmful are Juncus sp., Nepeta Glechoma, and Hieracium Pilosella.