The spines (Fig. 716) are not connected with the axis of the stem or branches, but emerge from the areoles. In some forms they are simple and straight, bristle-like, awl-shaped, or short and conical. In others they are bent like fishhooks or are curved and horn-like, with transverse ribs. Sometimes they are minutely downy or hairy and sometimes even plumose or feathery. They may be either naked or enveloped in a membranous barbed sheath (Fig. 717). They may be grouped in starlike clusters, with straight or curved rays spreading from a common center, or in comb-like fascicles, with the radial spines arranged in two rows on each side of a longitudinal axis (pectinate) . In addition to the radial spines, there are usually erect central spines either straight and rigid, or more or less curved. One of the most striking forms is that of the organ cactus, Myrtillocactus geometrizans, in which the stout erect central spine resembles the blade of a dagger and the radials a guard for the hilt. In contrast with this may be mentioned the spines of Pelecyphora aselliformis, which resemble miniature sow-bugs, or aselli (Fig. 718).

The flowers in most cases issue from the upper portion of the areoles, but in certain mamillarias and allied forms they come forth from between the tubercles or from their base at the end of a dorsal groove. Usually the flowers are solitary and sessile, but in the genus Pereskia

(Fig. 714) they are peduncled and often clustered. They may be tinted with rose-color, crimson, purple, yellow or orange, or rarely with copper-color or scarlet, but they are never blue. Often they are pure white at first, gradually becoming suffused with rose-color in age. In a few species they are inconspicuous, as in the epiphytal Rhipsalis (Fig. 712). Some are diurnal, others nocturnal; some open at sunrise and close at night or when the sky becomes clouded; others open at a certain hour and close at another fixed hour of the day or night; some last for only a few hours, others for a day, and some persist for several days. Some, like the "night - blooming cereus" are delightfully fragrant, while others are ill-smelling or have no perceptible odor.

Cactus Cacti 27Leuchtenbergia principis, showing transformation from scales to petals.

Fig. 720. Leuchtenbergia principis, showing transformation from scales to petals.

The perianth is not divided sharply into calyx and corolla, although the outer floral leaves are usually sepal-like and the inner ones are true petals. In one great division of the family including Opuntia, which has been named Rotatiflorae, the perianth is more or less wheel-shaped or widely spreading (Fig. 719); in the other division, Tubuliflorae, to which Cereus belongs, the floral leaves form a tube, often remarkably long and slender, and crowned with a spreading limb. The floral leaves are not arranged in definite series but somewhat like those of a water-lily, the scale-like lower or outer leaves gradually becoming broad and petaloid as they approach the center (Fig 720). In all cases the perianth crowns the ovary, and sometimes persists after withering on the apex of the fruit (Fig. 721). The stamens are very numerous and are inserted on the petals or perianth-tube

(Fig, 722). The single style is longer and stouter than the slender filaments, and usually terminates into a radially divided stigma (Fig, 723). Sometimes the stigma is conspicuously colored and issues star-like from the center of the mass of stamens, as in the genus Echinocereus, in which the emerald-green star contrasts prettily with the golden-yellow or orange-colored stamens, rising from a rosette of rose-purple petals (Fig. 724). The ovary (Fig. 723), although formed of several carpels, is 1-celled. The placentae are parietal, bearing an indefinite number of ovules, the stalks of which (funiculi) become fleshy as the seeds develop and form a sugary pulp around the seeds.

Extreme condensation of the plant body.   Pelecyphora aselliformis. (Nat. Size.)

Fig. 718. Extreme condensation of the plant body. - Pelecyphora aselliformis. (Nat. Size.)

Cephalocereus fruit.

Fig. 721. Cephalocereus fruit.

Echinocactus flower, showing insertion of stamens.

Fig. 722. Echinocactus flower, showing insertion of stamens.

Opuntia flower, showing styles and ovary.

Fig. 723. Opuntia flower, showing styles and ovary.

The fruits of the Cactaceae are variable in form. That of the leafy Pereskia is apple-shaped and bears a number of leaf-like bracts on the skin (Fig. 725), on which account the fruit of P. aculeata is called blad-appel, or leaf-apple, in the Dutch colonies, while in the British West Indies it is known as Barbados gooseberry and is made into tarts and sauces like real gooseberries. In some of the pereskiopses, the fruit is elongated and shaped like a prickly pear, with watery rind and seeds covered with cottony hairs. In Opuntia and Nopalea the fruit is commonly called prickly pear, or tuna (by the ancient Aztecs, nochtli). These fruits bear small fleshy leaves at first, like the flattened pads of the plants, and when the leaves fall off the areoles persist armed with the irritating sharp-barbed glochidia described above (Figs. 717 and 726). Many species allied to the genus Cereus bear edible fruits, usually called pita-hayas. Those of the tall columnar cardones (Lemaireo-cereus) are covered with easily detachable tufts of wool and spines but never bear glochidia. Those of Cephalo-cereus (Fig. 721) are spineless.

The triangular climbing forms which are often trained over garden walls in tropical countries, sometimes bear enormous juicy fruits of fine flavor (Fig. 727). Those of Echinocactus (Fig. 728) are more or less scaly. The fruits of certain species of Echinocereus, called alicoches by the Mexicans, are known to Americans as strawberry cacti, on account of the fine flavor of their juicy pulp. Those of Echinocactus longihamatus are known in northern Mexican markets as limas de viznaga, or cactus limes, on account of their acid taste; and the small smooth crimson fruits of many mamillarias are called chilitos, on account of their resemblance to small chili peppers. Very much like them are the fruits of melon cacti (Fig. 729) which issue from the dense crown of bristles like scarlet radishes or firecrackers tipped with a fuse. The seeds of the Cacta-ceae vary considerably in the different groups, and are sometimes useful in making generic determinations. Thus the woolly seeds of Pereskiopsis are sharply distinct from the black glossy seeds of the genus Pereskia, with which the first-named genus was at one time confused.

In Opuntia and Nopalea they are flat, hard and bony, somewhat ear-shaped in the flat-jointed opuntias (Figs. 730, 733,) and usually discoid and marginless in cylindrical opuntias (Figs. 730, 735). In Cereus they are glossy black, with the testa either quite smooth or minutely pitted (Figs. 730, 732); in Echinocereus they are covered with minute tubercles or granules (Figs. 730, 734). In Echinocactus, which is not a very homogeneous group, the seeds are pitted in some species and tuberculate in others In one section of Mamillaria (Eumamillaria) they are glossy and marked with sunken rounded pits (Figs. 730, 731), while in another section, which should probably be made a distinct genus (Cory-phantha) they are frequently smooth. In the closely allied Ariocarpus they are relatively large and tuberculate. In the genus Pelecyphora, they are sometimes kidney-shaped, as in P. aselliformis, and sometimes of a peculiar boat-like form with a very large umbilicus, as in P. pectinata. In the epiphytal Rhipsalis cassytha they are kidney-shaped and finely granular. The seeds of many of the species of Pachycereus ("cardones") are used by the Indians of Lower California and Mexico for food.

In southern Puebla the fruit of Pachycereus columna-trajani, called tetezo figs (higos de tetetzo) are a regular food staple, offered for sale in the markets of Tehuacan d u r i n g the month of May.

Echinocereus flower, showing radiate stigma.

Fig. 724. Echinocereus flower, showing radiate stigma.

Pereskia fruit.

Fig. 725. Pereskia fruit.

Opuntia fruit.

Fig. 726. Opuntia fruit.

Seeds of Cacti. 1. Mamillaria; 2. Cereus; 3. Flat jointed opuntias; 4. Echinocereus; 5. Cylindrical opuntias.

Fig. 730. Seeds of Cacti. 1. Mamillaria; 2. Cereus; 3. Flat-jointed opuntias; 4. Echinocereus; 5. Cylindrical opuntias.

Other cactus fruits of great economic importance are those of the giant Cereus of our arid southwestern region, Carnegiea gigantea, locally known as pitahayas de sahuara, first brought to notice in the year 1540 by the members of Coronado's expedition. They are not spiny like the fruits of Pachycereus and they burst open when quite ripe. The fruit of Lemaireocereus Thurberi, known as pitahaya dulce, although much sweeter, bears clusters of stout spines issuing from tufts of wool. Closely allied to it is Lemaireocereus griseus of central and southern Mexico, which yields much nutritious fruit. The fruit of the organ cactus, Myrtillocactus geometrizans, sold in the markets as garambullas, either fresh or dried, must also be mentioned as of economic importance.

Fruit of Hylocereus.

Fig. 727. Fruit of Hylocereus.

Of medicinal importance is the narcotic peyote or "mezcal button"

Fruit of Echinocactus.

Fig. 728. Fruit of Echinocactus.

Melon cactus bearing fruits.

Fig. 729. Melon cactus bearing fruits.

(Lophophora Williamsii), used as an intoxicant and febrifuge by certain tribes of Indians, and regarded by some of them with superstitious reverence. This little plant was regarded by some of the early Spanish writers as a fungus and was used by the Mexican Indians to produce marvelous visions.

For an account of the methods of propagation and culture of cacti and their application to ornamental gardening the reader is referred to a paper by Charles Henry Thompson, on "Ornamental Cacti: Their Culture and Decorative Value," issued by the United States Department of Agriculture as Bulletin No. 262 of the Bureau of Plant Industry, December 17, 1912. See also Succulents, vol. VI. W. E. Safford.