CAC'TEE, or CACTA'CE.E, a natural order of exogenous plants, consisting of succu lent shrubs of very singular appearance. Linnaeus included all the C. in the single genus cactus, which is now divided into a number of genera; the name cactus, however, Still continuing in popular use, common to the whole order. Nearly 500 species are known, but the real number is probably much greater. The C. are, without exception, natives of America, and their extraordinary forms constitute a remarkable feature in the vegetation of its warmer regions. All of them have fleshy stems. either simple or branched, often very soft and juicy; but in many, at least when old, having an easily distinguished woody axis, composed of annual rings, and covered with a layer of inner bark, so that the thick fleshy part may be regarded only as a layer of bark. Most of them are leafless; the pereskhr alone have true leaves, which are fleshy; and the have rudimentary leaves, which soon fall off; but, instead of leaves, most of the order have clusters of hairs or prickles, where buds are formed in their stems, and these are very numerous, even in the species which in ordinary circumstances most rarely develop branches. The multiplicity of curious forms exceeds imagination; in many species (melocacticke,or melon thistles),the stem swells out into a globe; in others (torch thistles),it rises up as a column with many angles; in others (opuntice, Indian figs, or prickly pears), it divides in leaf-like articulations; in some (pereskia) it assumes a tree-like form, in which the thick stem bears a head of branches, and reaches a considerable height, some times even 30 or 40 feet. Those which have angular, ribbed, and channeled, or fiat and two-edged stems, show a tendency to the cylindrical form as the stem advances in age. Some species have lona. creeping or trailing stems. The whole organization of the C. adapts them for the endurance of long droughts; they vegetate vigorously during a part of the year, and then rest; the very absence of leaves concurring with the absence of pores or stomata in their tough skin to enable them to resist the action of a dry atmos phere and powerful sunshine, and to occupy arid soils and bare rocks, on which they are very generally found, often covering large tracts. Some of them grow rapidly on
old lavas, and disintegrate them by their penetrating roots, thus preparing a soil for other plants; and the prickly pear is often planted in Sicily by the mere insertion of a branch or joint of it in a fissure of lava. Many species occur as epiphytes (q.v.) on the trees of American forests. Some also grow on high mountains, a few even reaching almost to the border of the snow. The plants of this order are a great boon to the regions in which they chiefly abound, which are, at least during great part of the year, very destitute of water; their stems containing a store of insipid and wholesome juice, of which both men and cattle avail themselves.—Some species, as the prickly pear (q.v.), produce a pleasant fruit.—The fruit of opuntia tuna affords a valuable pigment of the richest carmine color.
The flowers of the C. are in general very short-lived; those of some night-flowering species, as of cereus grandiflorus, well known in our hothouses, endure only for part of a single night. In the greater number, they are large and splendidly colored, in some they are very fragrant. The order is regarded as botanically allied to me.sembryacea (q.v.) and to grossulariacece (q.v., gooseberry, currant, etc.).
The cultivation of the C. in green houses and hothouses has been much in fashion for more than 30 years. The gardener must imitate the natural conditions of their growth, by giving water freely during a few months, and withholding it almost entirely during the rest of the year. Most of them are easily propagated by branches, taken off, and allowed to dry a little before being planted. The mdocactida, which do not readily produce branches, are made to do so by cutting off or burning out the central bud, that the means of propagating them may be obtained.