CACTUS (from kaktos, a name used by Theophrastus to describe a spiny plant). This generic term is popularly applied to all members of the extensive family Cacteæ, which order may be distinguished by the following characteristics: Calyx composed of many sepals, usually indefinite in number, the inner series not readily distinguishable from the petals, united and adnate a great length to the ovary; with the tube smooth in the genera Mammillaria, Melocactus, and Rhipsalis; or with the lobes of the sepals crowning the fruit, and having the tube scaly, as in the genera Cereus, Opuntia, and Pereskia. Petals disposed in two or more series, hardly distinguishable from the inner sepals, and somewhat united to them; sometimes irregular, and disposed in a long tube at the base, but distinct at the apex, as in the genera Mammillaria, Melocactus, and Cereus; sometimes equal and distinct to the very base, forming a rotate corolla, as in the genera Opuntia, Pereskia, and Rhipsalis. Stamens indefinite, disposed in many series, more or less cohering with the petals or inner sepals; filaments slender, filiform; anthers ovate, versatile, two-celled. Ovarium obovate, fleshy, one-celled. Fruit fleshy, one-celled, many seeded, either smooth and crowned by the calyx, or covered with scales, scars, or tubercles, and umbilicate at the apex. This order contains fleshy or succulent shrubs, very variable in habit and size. Flowers very variable, showy, or minute, usually solitary, sessile, rarely in fascicles, ephemeral, expanding by night or day. Leaves usually wanting, but, when present, small, caducous, and terete, rarely flat and expanded, sometimes alternate and disposed in a spiral order, always glabrous and fleshy. Prickles or bristles disposed in fascicles, rising from the axils of the leaves. In the leafless genera, the fascicles of spines are disposed on the angles of the stem, rising from tubercles. Stems usually angular, winged, or regularly beset with tubercles, rarely terete, usually jointed; joints compressed. A group of Cacti is shown at Fig. 312, for which we are indebted to Herr Fr. Ad. Haage, jun., of Erfurt, Germany. See Cereus, Disocactus, Echinocactus, Epiphyllum, Leuchtenbergia, Mammillaria, Melocactus, Nopalea, Opuntia, Pelecyphora, Pereskia, Phyllocactus, and Rhipsalis.

Cultivation. Perhaps no class of plants more easily accommodate themselves to a general system of treatment, than do these; although certain genera would undoubtedly thrive better than when subjected to the lower temperature, suited to the requirements of those coming from cooler regions. Notwithstanding that nearly all the species are natives of the western hemisphere, they occur in various geographical and altitudinal areas, in which the temperature is proportionately lessened or increased, as the case may be; yet, presuming a special house is set apart for their culture, the majority of the species may be happily suited therein. The warmest end of the structure should be selected for the tropical kinds; while those found in cooler regions may be grown in the other portions of the house; even those which are hardy in our climate are really best wintered in a house or frame. Granted that several species will endure our winter outside, it is yet necessary to give them the shelter of a friendly ledge of the rockery, or frame, or to cover them in their permanent position with a hand light, or sheet of glass, in order to prevent the ill-effects of excessive moisture. Generally, a winter temperature of from 50deg. to 55deg., and a summer one of from 70deg. to 80deg. during shade, or in sunshine up to 90deg., will be found advantageous. When thus treated, it will be necessary to keep the tropical species, on the whole, very dry during the winter. As regards soil, potting, and general treatment, all may be treated alike, except Epiphyllum, Disocactus, and Pereskia (which see). Some growers give them the protection of a house in winter, and stand them outside during the summer, which is not, however, a very commendable plan, as, in consequence of the very variable character of our climate being especially prejudicial to several of the tender and more delicate species, the often excessive amount of moisture they would receive, will produce a weakly state of health in many, while others will be lost. It is far better if their culture is attempted at all, to give them the proper treatment. The numerous species and varieties found on the Rocky Mountains are a most interesting series, and may be well managed in a cold frame facing south, arranging them on shelves as close to the glass as possible, and keeping them very dry through the winter. If the weather is very severe, the lights should be matted. One of the best collections of these in the country, is in the possession of E. G. Loder, Esq., Floore House, Weedon, Northampton, where a great number are admirably grown in frames, and under a large ledge of the rockery outside. Amateurs may grow quantities of handsome Cacti either in dwelling rooms near the window, or in small frames or greenhouses. As they are slow growing, not much space will be occupied; at the same time, a great deal of interest will be centred in their culture. As regards watering and insect pests, they are but little trouble. Miniature Cacti, of numerous kinds, are now often sold in small pots, and most attractive little subjects they prove.

1. Opuntia.
2. Cereus.
3. Opuntia streptacantha.
4. Cereus candicans.
5. Mammillaria.
6. Cereus peruvianus monstrosus.
7. Echinocereus electracanthus.
8. Mammillaria.
9. Echinopsis formosa.
10 Echinocactus Visnaga.
11. Cereus peruvianus var.
12. Opuntia candelabriformis.
13. Cereus strictus.
14. Pilocereus senilis.
15. Cereus Tweedii.
16. Cereus chilensis.

FIG. 312. GROUP OF CACTI.

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Soil, Drainage, and Potting. Good ordinary fibrous loam should form about one-half of the compost, the other half should be made up of sand, broken bricks, and lime rubbish in equal quantities; the whole to be carefully mixed together, and not used until it is moderately dry. It is absolutely necessary to ensure perfect drainage; a good "stopper" should, therefore, be placed over the hole at the bottom of the pot, and about one-third of its depth filled with draining material. The best time for potting is during February and March. Turn out the plants, and remove nearly all the old soil from the roots, taking away any dead or decaying roots which may be observable. Place some of the roughest soil next the crocks, and gradually fill the pots with the finer material, well working the same amongst the roots; finally press the soil moderately firm. Do not water for a few days after potting, but syringe every evening, especially if the weather be fine; a little extra heat may be given after potting, to excite new, healthy growth. It will not be necessary every year to repot specimens in large vessels. A good top-dressing, with an occasional dose of weak liquid manure, is all they will require for several seasons.

Watering. This must be discriminately managed, especially during the winter; for, whatever their treatment as regards temperature during that season, they must be studiously watered, and anything like a saturated condition of the soil should be avoided. If the temperature is brisk, a little water may be given once a week, or perhaps not quite so often. If the plants are subjected to very cool treatment, water must be sparingly administered during November, December, and January; after which, they should be examined weekly, and very carefully attended to. During the summer months, when in active growth, they will not suffer if watered twice a week; and, on bright afternoons, light syringings may be advantageously given.

Propagation. Three methods are adopted, viz., by cuttings or offsets, grafting, and seeds; the former is the plan generally adopted. The cuttings or offsets should be removed with a sharp cut, and laid upon a sunny shelf until the wound is healed and roots are emitted, when they should be potted in sandy soil, and placed with the others. They will thrive freely if kept syringed. Grafting is resorted to with delicate kinds, which, from some reason or another, will not grow freely except upon the stock of a stronger species; and, by this means also, such delicate kinds can be kept from the damp soil, which frequently causes incipient decay. The stocks usually employed are those of Cereus tortuosus, C. peruvianus, &c., according to the species intended for working; they readily unite with each other. If the scion and stock are both slender, wedge-grafting should be adopted; if both are broad, it is best to make horizontal sections, placing them together and securing in proper position by tying with matting, but not too tightly, or the surface may be injured. Propagation by seeds is not often adopted, as it is a very slow method; they should be sown in very sandy soil, and placed in a semi-shady position until germination commences, when they may be exposed, and very carefully watered.

CACTUS DAHLIA. See Dahlia Juarezii.