Cactus
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Cactus
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| Standard Cyclopedia of Horticulture |
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Cactus or cacti. The plants correctly designated by this name constitute the family Cactaceae. Scarcely any group in the whole plant kingdom is more remarkable for its strange and varied forms, the beauty of its flowers, and wonderful adaptation to desert life. It is not, however, confined to desert regions; for in the moist forests of the tropics of the New World it is represented by a number of interesting forms often epiphytal or scrambling in their habit of growth, with beautiful flowers and sometimes with delicious edible fruit.CH RangeThe Cactaceae are confined to America, the only apparent exception being the genus Rhipsalis, composed of plants with the habits of the mistletoe, growing on the trunks and branches of trees, and bearing small pellucid glutinous berries. This genus, endemic in tropical America, has found its way to Africa, the island of Mauritius and even to Ceylon; and several opuntias, or prickly pears, occur on the shores of the Mediterranean, in South Africa, and Australia, where they have made themselves so thoroughly at home as to be regarded by many writers as indigenous. The Cactaceae are not confined to tropical or even semi-tropical regions. At least two species of Opuntia extend northward into British Columbia, and species of Echinocereus, Echinocactus, and Mamillaria are found in the state of Colorado. The xerophytic forms flourish especially in the southwestern United States, the Mexican plateau, the peninsula of Lower California, where there are great cactus forests, and the vicinity of Tehuacan, in the southern part of the Mexican state of Puebla, a region celebrated for its remarkable and gigantic tree-like forms related to the genus Cereus.CH To the southward, the family extends to Chile and Argentina. Giant torch thistles and echinocacti are scattered over the pampas of Uruguay, and melon-shaped echinopses amid the snows of the lofty plateau of Bolivia.CH The genus Mamillaria, so well represented in the southwestern United States and Mexico, is almost absent from Central America, the representative genera of that region as well as of the warm Huasteca region of eastern Mexico being Cereus, Pereskia, Pereskiopsis, Nopalea, and Opuntia; while the "turk's-head” or "melon cacti" are chiefly West Indian.CH Structure  The peculiar structure of columnar, opuntioid, and melon-shaped cacti is undoubtedly the result of excessive dryness of the climates in which they occur, to protect themselves from which they have been obliged to store up water and to reduce their transpiration as low as possible. They have a more or less pronounced woody axis surrounded by pulpy cellular tissue (parenchyma) in which the water-supply is stored. The stomata are usually situated in depressions or grooves in the leathery cuticle; and as an additional means for checking transpiration, the cell-sap is nearly always mucilaginous, while in some forms latex cells are present, filled with milky or gummy fluid which hardens on exposure to the air and effectively heals wounds in the soft fleshy plant. Certain species of Echinocactus (viznagas) are like great barrels studded with spines and filled with pulp of the consistency of watermelon rind, which is sometimes made into conserves like citron (dulces de viznaga). Other forms, like species of Pereskia, Pereskiopsis, and arboreous opuntias have hard, woody stems and branches. The reticulated skeletons of certain species of opuntia are manufactured into walking-sticks, legs of furniture, napkin rings, and even into veneering for woodwork. In Lower California and some parts of South America, where other vegetation is lacking, the stems of columnar cerei, or "cardones," are used for constructing habitations, inclosures, and for timbering mines. Columnar cacti are also planted for living fences, or hedges, especially the "organ cactus" (Myrtillocactus geometrizans) of tropical Mexico. Leaves are present in nearly all cacti, but in some species they are mere vestiges and can scarcely be seen with the naked eye. In other species they are large and perfectly developed, either with distinct petiole and feather veins, as in Pereshia aculeata, or sessile and fleshy with only the midrib and several parallel nerves apparent as in the genus Pereskiopsis. They are sometimes caducous, fleshy, cylindrical or awl-shaped, as in the genus Opuntia. In the axils of the leaves are peculiar cushion-like areoles (corresponding in all probability to aborted branches) clothed with down or felt-like wool, from which spines, and, in some genera, also flowers, issue. In the genera Opuntia and Pereskiopsis, the areoles also bear minute short barbed bristles called glochidia, which will penetrate the skin and become detached at the slightest contact and are the source of annoying irritation which often persists for many hours.CH Spines The spines 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. They may be grouped in star-like 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.CH Flowers  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 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. 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.CH 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: 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. In all cases the perianth crowns the ovary, and sometimes persists after withering on the apex of the fruit. The stamens are very numerous and are inserted on the petals or perianth-tube. The single style is longer and stouter than the slender filaments, and usually terminates into a radially divided stigma. 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. The ovary, 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.CH Fruits 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, 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. Many species allied to the genus Cereus bear edible fruits, usually called pitahayas. Those of the tall columnar cardones (Lemaireocereus) are covered with easily detachable tufts of wool and spines but never bear glochidia. Those of Cephalocereus are spineless. The triangular climbing forms which are often trained over garden walls in tropical countries, sometimes bear enormous juicy fruits of fine flavor. Those of Echinocactus 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 which issue from the dense crown of bristles like scarlet radishes or firecrackers tipped with a fuse. The seeds of the Cactaceae 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 and usually discoid and marginless in cylindrical opuntias. In Cereus they are glossy black, with the testa either quite smooth or minutely pitted; in Echinocereus they are covered with minute tubercles or granules. 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, while in another section, which should probably be made a distinct genus (Coryphantha) 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 columnatrajani, called tetezo figs (higos de tetetzo) are a regular food staple, offered for sale in the markets of Tehuacan during the month of May.CH 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.CH Of medicinal importance is the narcotic peyote or "mezcal button" (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.CH
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Species
Selected important generawp
- For a full list see Taxonomy of the Cactaceae
Gallery
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Blooming Echinopsis. The sweet-smelling flower opens towards evening and dies the following morning.
Ferocactus pilosus (Mexican Lime Cactus)
photo 2
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References
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
