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ON THE GENUS EUPHORBIA.
BY JOHN R. JACKSON, A.L.8.,
Curator of the Museum, Royal Gardens, Kew.
(With a Coloured Plate.)
The natural order, Euphorbiaceæ contains some of the most curious forms of plant life to be found in the vegetable kingdom. The species have a wide geographical range, being found in Africa, North America, India, and Europe, their head-quarters, however, is in equinoctial America. The characteristic properties of the order are acrid and poisonous, most of the plants abound in a milky juice ; some, however, yield oils, as the castor oil and the croton oil ; some starch, as cassava or tapioca; and some caoutchouc—the principal commercial source of which is Siphonia brasiliensis, and S. elastica, both plants belonging to the Euphorbiacea. The poisonous principle of this order appears to be volatile, the application of heat in most cases removing it, as is instanced in the cassava root, which is a violent poison in its raw state, but when cooked becomes a nutritious food.
It is to the genus Euphorbia, which gives its name to the order, that we are now more especially concerned; it comprises a very large number of species distributed nearly all over the world, and varying very considerably in their general appearance. In the warmer regions of the southern hemisphere they grow to the size of shrubs or small trees, while in the more temperate parts of the northern hemisphere they are mostly herbaceous. The plants bear monacious flowers, arranged in heads, surrounded by bracts, which, in some species, are of a bright scarlet colour. These bracts form an involucre, more or less cup-shaped, but lobed or toothed; the lobes, which are four or five in number, alternating with numerous glands. In the centre of the involucre is a single three-celled stalked ovary, surrounded by what appears at first sight to be numerous stamens, and so giving to the flower-head the appearance of being a single flower; upon a closer examination, however, it will be seen that each stamen is jointed in the middle, and has a distinct scale at its base, so that in fact each one of these apparent stamens is a separate male flower arranged round a central-stalked female flower; the ovary being surmounted by a three-cleft style. The fruit is composed of three, usually very distinctly lobed, one-seeded carpels. Though the
VOL. III.- NO. VI.
botanical characters hold good in all the species, the general forms, as we have before remarked, vary very much according to their geographical position.
Some idea of the habits and tree-like forms of some of the African species may be obtained from the coloured plate which is from a drawing by Mr. Baines, to whom I am indebted for much of the following information on the general characters of the plants inhabiting those regions of Africa traversed by him. Among the many curious forms of vegetation distributed over that section of the globe, the Euphorbias claim a prominent position as well for their extended range as for the great variety of forms they assume, for while some are dwarf and cactus-like, destitute of any leaves, but forming thick fleshy stems, others are tall and straight, with nearly square or flat-sided stems, while others again are nearly triangular with depressed sides, some are equal in thickness throughout their whole height, some compressed at intervals up the stem, of three, six, nine, or twelve inches, and all are more or less armed along the edges with short sharp spines or thorns.
In Africa the tall growing species-like Euphorbia grandidens, Haw., which grows to a height of thirty or forty feet,-form a peculiar feature in the landscape, while numerous smaller growing species are spread over the country, either crouching low upon the ground in single plants, or growing in clusters from the clefts of the rocks. E. grandidens is one of the species cultivated in greenhouses on account of their singular appearance. It sends out from its main stem whorls of branches, candelabra fashion. I received at the Museum, a few years since, a fresh specimen of the trunk of this species, and kept it in a tolerably warm room, hoping by that means to dry it gradually and so preserve it, but so succulent was its nature, and so highly charged with milky juice, that it remained some months without any visible diminution of its bulk, keeping perfectly green, and the milk flowing from it upon the slightest fracture of the bark. At the expiration of a year the outer portion of the stem began to shrivel, and at the end of sixteen or eighteen months, it had become quite separated from the inner or heart wood, and hung round it like a coat several sizes too large. Amongst the smaller forms of South African Euphorbiæ, Euphorbia caput-medusæ is one of the most common, it grows in a hemispherical mass composed of a number of fleshy stems or branches about the thickness of a man's finger. Its head quarters is at the Cape of Good Hope. A species having a somewhat similiar habit seems to be common in Abyssinia, judging from the photographs taken during the late campaign, some exceed
ingly fine specimens of the plants appearing in a view of the church at Attegerat.
The juice of E. caput-medusa, like most of the other species, is thick and milky, exceedingly acrid and poisonous, so that the natives use it both to poison their arrows and to pour into the pools of water where fish abound for the purpose of capturing them. Mr. Chapman, the African traveller, speaks in his journal of an excursion he made, accompanied by one of his boys, into the mountains for the purpose of collecting some of the milk of the Euphorbia, and notwithstanding the greatest caution imposed upon the boy, he allowed a thorn to prick his hand on which he had some of the milk; no blood came from the wound, but he soon began to feel intense pain, which increased, and in four or five days time he had to be carried into the waggon, the excruciating pain and sickly feelings becoming alarming, blisters arose on his skin wherever he had scratched himself with the thorns, although great care had been taken to see that he washed his hands immediately after handling the poison. Mr. Chapman says:-It was evidently a very near go with him, I did not know what medicines to give him. I gave him the usual remedies; but think his life was saved by the juice not getting properly, or plentifully, into his blood. The plant said to have been discovered in Barbary in the time of King Juba, and named by him after his physician Euphorbus, is referred by some to E. officinarum, L., a very angular succulent species armed along its edges with double spines, and which now grows in the north of Africa, others consider it to have been E. antiquorum, L., a species very widely dispersed over Africa, the East Indies, etc., having triangular or quadrangular branches thickly studded at the angles with very sharp spines. The gum-resin, known in commerce as Euphorbium, and which occurs in small irregular yellowish tears frequently pierced with holes, and often with the remains of the spines of the plants imbedded in them is no doubt produced partly by the two above-named species, E. Canariensis, E. tetragona, and probably several other species lending their aid. The Euphorbium of the shops is procured from Barbary, the natives collect it by making incisions in the branches of the plants and allowing the juice to flow from them, it soon hardens by the heat of the sun, while it still remains attached to the stem, after a time, however, the lumps fall off and are collected, the collectors being very cautious how they handle them, the gum being so acrid that it soon excoriates the skin, and the dust and small particles are so apt to enter the mouth and nostrils, producing con
tinued irritation and incessant sneezing, that the natives protect those organs by tying a cloth over them.
The chief physiological effects of Euphorbium upon man is that of a most violent acrid, the pain and irritation to the eyes and nose, endured by those occupied in grinding this drug, is said to be intense, various contrivances have been adopted to protect them, such as masks, coverings of crape, etc. Continued exposure to the influence of the dust produces headache, giddiness, and delirium. Pereira says, that an old labourer at one of the drug mills assured him that this substance produced in him a feeling of intoxication, the same writer also mentions the case of an Irish labourer who was made temporarily insane by it, and who, during the fit, insisted on saying his prayers at the tail of the mill-horse. The following case, in which insensibility and convulsions have been produced by Euphorbium, is also recorded :-A man was engaged at a small mill where Euphorbium was being ground, and remained in the room longer than was considered prudent. Suddenly he darted from the mill-room, and ran with great velocity down two pair of stairs. On arriving at the ground floor, or yard, he became insensible, and fell. He was attended to within five minutes when he was found lying on his back, insensible and convulsed; his face was red and swollen, his pulse frequent and full, and his skin very hot. He was bled, and within half an hour he became quite sensible, but complained of great headache. He had no recollection of his flight downstairs, which seemed to have been performed in a fit of delirium.
Dr. Christison mentions two experiments on the effects of Euphorbium, upon dogs; in the first, half an ounce of powdered Euphorbium was introduced into the stomach and retained there by a ligature on the gullet. The dog died in twenty-six hours and a half, an examination of the animal showed the whole coats of the stomach, but especially the villous membrane to be of a blackish red colour; the colon and the rectum, especially the latter, were of a lively red internally, and their inner membrane was checkered with little ulcers. In the second case, two drachms of the powder was inserted in a wound made in the thigh, and secured by covering it with the flaps of the incision, the dog exhibited no other remarkable symptoms, but great langour, but died in twenty-seven hours, the limb and a portion of the body was found after death to be much inflamed.
Euphorbium when taken internally by man, produces vomiting and purging, and large doses bring on cold perspirations,