Considered from the layman's point of view, cacti are made up of two classes: those which are valued for their wonderful flowers and those which excite curiosity by their weird habits of growth. Some of the latter—such as the Crown of Thorns and the Mammillaria—have small or infrequent flowers.
Specimens of this class, well cared for, are worthy of a place in any collection of flowering plants. They will stand, especially during the flowering period, weak applications of manure water.
The Epiphyllums or Crab cacti (Ephiphyllum truncatum and its varieties) are by far the most valuable, because of their profuse and long flowering season, especially as it comes in the winter when bright flowers are scarce. E. t. coccineum, with deep scarlet flowers, is one of the best. Ruckerianum, light purple with violet center; Magnificum, white, slightly pinkish at the edge; and violaceum superbum, white with rich purple edge, are some of the other good varieties of these beautiful plants. Phyllocactus is perhaps the next best flowering sort. The flowers are larger, more gorgeous, but borne only for a very short time. P. Ackermanni is one of the best of these. It has very large flowers, lily-shaped, bright red shading to light red with the inner petals, and the long gracefully curved stamens add to its beauty. It blossoms in May or early June, but the season is usually limited to two or three weeks. The night blooming Phyllocactus, with white flowers, is commonly confused with the Night-Blooming cereus. Cereus may be distinguished by its angular stems as compared to the broad flat stems of Phyllocactus. C. grandiflorus and C. Macdonaldiae, the famous Night-blooming cereuses, have white flowers which remain open only one night. They are, however, though so transient, a marvelous sight. Prone to strange tasks indeed is the hand of Nature which has fashioned these grotesque, clumsy, lifeless looking plants to accumulate nourishment and moisture for months from the niggardly desert sands, and to mature for a few hours' existence only these marvelously fashioned flowers which collapse with the first rays of the heat-giving sunshine. C. flagelliformis, and C. speciosissimus, two very gorgeous flowered day blooming sorts, remain longer, but they are not so hardy as most of the other cacti. Opuntia, the Indian fig, is another flowering sort, though not so valuable. They are grotesque in shape and the flowers, which are various shades of red or yellow and two inches or so across, according to variety, look as though they had been stuck onto the plant.
Of the other cacti commonly grown most are of dwarf form and a single window will accommodate quite a number of them.
Echinocactus, the Hedge-hog cactus, is one of the best known of these. E. myriostigma, the Bishop's Cap, is a quite familiar variety.
Echinopsis, the Sea-urchin cactus, is another queer dwarf type. The flowers seem much too large for the plants, being sometimes half a foot long. They are lily-shaped and rose pink or white, according to variety.
Pilocereus senilis, the Old Man cactus, is another sort which always attracts attention in any collection. The stem is covered with fine white hairy spines, three to five inches long, which give it a very peculiar appearance. When kept in the house the hairs are likely to become dusty and grimy. They may be protected by cutting two panes of glass into four long pieces, just wide enough to square the pot, and enclosing it, putting a fifth piece over the top.
Opuntia senilis, the dwarf prickly pear, is very similar to the above, but indoors makes a larger plant usually, although much smaller in its natural habitat.
Anhalonium fissuratum, the Living Rock, is an other frequently encountered and very interesting sort.
The Mammillarias are compact, neat little plants quite unique and attractive in spite of their spiral rows of vicious spines. They grow only a few inches high and have inconspicuous pale flowers of yellow, red or purple, followed by the bright red little fruits which are one of the most interesting characteristics. M. bicolor is one of the best and most frequently encountered sorts. M. plumosa has fuzzy spines, like the Old Man cactus. It can be kept clean by growing under a large glass.