melon-thistle; a genus of the monogynia order, belonging to the icofandra class of plants. To this genus Linnaeus has added the cereus and opuntia; but to avoid the embarrassment occasioned by the description of such a variety of species, we choose, with Mr Miller, to describe them as three distinct genera. See CERES and OPUNTIA.

Species. 1. The melocactus, with 14 angles, commonly called great melon-thistle. 2. The intortus, with 15 angles spirally twisted, and erect spines. 3. The recurvus, with 15 angles, having broad recurved spines set very close. 4. The mamillaris, closely covered with bearded tubercles; or smaller American melon-thistle. 5. The proliferus, or small chilting melon-thistle.

All the species of this genus are plants of a singular structure, but especially the larger kinds of them; which appear like a large, fleshy, green melon, with deep ribs, set all over with strong sharp thorns; and, when the plants are cut through the middle, their inside is a soft, pale-green, fleshy substance, very full of moisture. The fruit of all the species is frequently eaten by the inhabitants of the West Indies. The fruits are about three quarters of an inch in length, of a taper form, drawing to a point at the bottom toward the plant, but blunt at the top where the emplacement of the flower was situated. The taste is agreeably acid, which in a hot country must render the fruit more grateful.

These strange plants commonly grow upon the steep sides of rocks in the warmest parts of America, where they seem to be thrust out of the apertures, having little or no earth to support them, their roots shooting down into the fissures of the rock to a considerable depth; so that it is difficult to get the plants up, especially as they are so strongly armed with thorns as to render it very dangerous to handle them. The large kinds were some time ago brought over to England in much greater plenty than of late; but many of them were destroyed by the unkindnesses of those persons who had the care of them in the voyage; for, by giving them water, they generally caused them to rot before they were taken out of the ships; and some of those which appeared to be found, were yet so replete with moisture, that they rotted soon after they were placed in the flores. Whoever therefore purposes to bring these plants from abroad, should be very careful to take up their roots as entire as possible, and to plant them in tubs filled with stones and rubbish, having very little earth in it. Three or four plants also ought to be put into each tub, in proportion to their size, in order to save room; for they will not increase in bulk during their passage, and no room needs be allowed them for this purpose. There should be several pretty large holes bored through the bottoms of these tubs, to let the moisture pass off; and if the plants are set in the tubs a month or more before they are put on shipboard, they will at that time have put forth new roots, which will be the best method of making them succeed. All the time they remain in their natural country they should have very little water given them, and after they are put on board they must have none at all. When they are brought to Britain, the larger sorts require a very good stove to preserve them through the winter, nor should they be exposed to the air in summer; for although they may continue fair to outward appearance, yet when they have been for some time exposed abroad, they will imbibe moisture sufficient to kill them on their readmission to the stove, and this will happen very suddenly; scarce any appearance of disorder will be observed till the whole plant is killed, which in a few hours time has often been the fate of the plants when first placed in the stove. If these plants are plunged into a hot-bed of tanners bark in summer, it will greatly forward them in their growth; but when this is practised, there should be scarce any water given to the plants; for the moisture which they will imbibe from the fermentation of the tan will be sufficient, and more would cause them rot. The best method to preserve all the large kinds is, in winter to place the pots either upon the top of the flues, or at least very near them, that they may have the warmest place of the stove, and never to give them any water. The soil in which they are planted must be of a sandy nature, and if mixed with some dry lime rubbish will be still better. In the bottom of the pots should be placed some stones, in order to drain off any moisture that may be in the earth; for as these plants grow naturally upon the hot, dry, burning rocks, which have no earth, and were it not for these plants would be absolutely barren, we must imitate their natural soil as near as possible, making some allowance for the difference of climates. The great sorts may be propagated from seeds; but as the plants which are raised from seeds in this country will be some years in arriving at any considerable size, it will be much the best way to procure some plants from the West Indies. The two small sorts propagate so fast, the fourth by seeds, and the fifth from the young plants thrust out from the sides of the old, that it is unnecessary to send for any of them from abroad.