This group bears the common name of torch thistle. It comprises about 100 species, largely Mexican but scattered through South America and the West Indies. The stems are columnar or elongated, some of the latter creeping on the ground or climbing up the trunks of trees, rooting as they grow. C. giganteus, the largest and most striking species of the genus, is a native of hot, arid, desert regions of New Mexico, growing there in rocky valleys and on mountain sides, where the tall stems with their erect branches have the appearance of telegraph poles. The stems grow to a height of from 50 ft. to 60 ft., and have a diameter of from 1 ft. to 2 ft., often unbranched, but sometimes furnished with branches which grow out at right angles from the main stem, and then curve upwards and continue their growth parallel to it; these stems have from twelve to twenty ribs, on which at intervals of about an inch are the buds with their thick yellow cushions, from which issue five or six large and numerous smaller spines.
The fruits of this plant, which are green oval bodies from 2 to 3 in. long, contain a crimson pulp from which the Pimos and Papagos Indians prepare an excellent preserve; and they also use the ripe fruit as an article of food, gathering it by means of a forked stick attached to a long pole. The Cereuses include some of our most interesting and beautiful hothouse plants. In the allied genus Echinocereus, with 25 to 30 species in North and South America, the stems are short, branched or simple, divided into few or many ridges all armed with sharp, formidable spines. E. pectinatus produces a purplish fruit resembling a gooseberry, which is very good eating; and the fleshy part of the stem itself, which is called cabeza del viego by the Mexicans, is eaten by them as a vegetable after removing the spines.
Pilocereus, the old man cactus, forms a small genus with tallish erect, fleshy, angulate stems, on which, with the tufts of spines, are developed hair-like bodies, which, though rather coarse, bear some resemblance to the hoary locks of an old man. The plants are nearly allied to Cereus, differing chiefly in the floriferous portion developing these longer and more attenuated hair-like spines, which surround the base of the flowers and form a dense woolly head or cephalium. The most familiar species is P. senilis, a Mexican plant, which though seldom seen more than a foot or two in height in greenhouses, reaches from 20 ft. to 30 ft. in its native country.
Echinopsis is another small group of species, separated by some authors from Cereus. They are dwarf, ribbed, globose or cylindrical plants; and the flowers, which are produced from the side instead of the apex of the stem, are large, and in some cases very beautiful, being remarkable for the length of the tube, which is more or less covered with bristly hairs. They are natives of Brazil, Bolivia and Chile.
Fig. 3. - Branch of Phyllocactus much reduced; the flowers are 6 in. or more in diameter.
Phyllocactus (fig. 3), the Leaf Cactus family, consists of about a dozen species, found in Central and tropical South America. They differ from all the forms already noticed in being shrubby and epiphytal in habit, and in having the branches compressed and dilated so as to resemble thick fleshy leaves, with a strong median axis and rounded woody base. The margins of these leaf-like branches are more or less crenately notched, the notches representing buds, as do the spine-clusters in the spiny genera; and from these crenatures the large showy flowers are produced. As garden plants the Phyllocacti are amongst the most ornamental of the whole family, being of easy culture, free blooming and remarkably showy, the colour of the flowers ranging from rich crimson, through rose-pink to creamy white. Cuttings strike readily in spring before growth has commenced; they should be potted in 3-in. or 4-in. pots, well drained, in loamy soil made very porous by the admixture of finely broken crocks and sand, and placed in a temperature of 60°; when these pots are filled with roots they are to be shifted into larger ones, but overpotting must be avoided.
During the summer they need considerable heat, all the light possible and plenty of air; in winter a temperature of 45° or 50° will be sufficient, and they must be kept tolerably dry at the root. By the spring they may have larger pots if required and should be kept in a hot and fairly moistened atmosphere; and by the end of June, when they have made new growth, they may be turned out under a south wall in the full sun, water being given only as required. In autumn they are to be returned to a cool house and wintered in a dry stove. The turning of them outdoors to ripen their growth is the surest way to obtain flowers, but they do not take on a free blooming habit until they have attained some age. They are often called Epiphyllum, which name is, however, properly restricted to the group next to be mentioned.