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Amaryllis Family (Amaryllidaceae)

flowering species leaves agave

Species in the amaryllis family are flowering plants, and are mostly long-lived, perennial herbs arising from a bulb or, less commonly, from rhizomes (underground stems). These plants have linear or strap shaped leaves, either crowded around the base of a leafless flowering stem, or arranged in two tight rows along a short stem, as in the common houseplant Clivia. The leaves are usually hairless and contain mucilage cells, or cells filled with calcium oxalate crystals known as raphides for defense against herbivores. Silica-filled (glass) cells, which are typical of many other monocotyledonous plant families, are absent from the amaryllis family.

The flowers of amaryllids are bisexual, with six perianth parts (or tepals) that sometimes have appendages A Joshua tree (Yucca brevifolia). Photograph by Gregory Ochoki. Photo Researchers, Inc. Reproduced by permission.

that form a corona, as in the central, protruding part of a daffodil flower (Narcissus spp.). The flowers are white, yellow, purple, or red, but never blue. The flowers are pollinated by bees or moths, but many are also adapted to bird and some to bat pollination. The fruits are usually many-seeded capsules, or sometimes berries.

Between 900 and 1,300 species of amaryllids have been recognized. Most are tropical or subtropical, with centers of distribution in South Africa, the western Mediterranean (especially Spain and Morocco), and to a lesser extent, Andean South America. Many species are drought-resistant xerophytes that produce leaves in the spring or when the rainy season begins, open their stomates only at night, have stomates located in the bottom of pits, and have thick waxy leaves—all to conserve water.

Many amaryllids are prized as ornamentals for home or garden because of their large, showy flowers, which are held high above the contrasting dark green leaves. The Cape belladona (Amaryllis belladona) is a native of dry regions of southwestern Cape Province, On the left, a flowering century plant (Agave shawii), and on the right a cirio (Idria columnaris), Baja California, Mexico. Some plant taxonomists include agaves in the amaryllis family, while others place them in their own family, the Agavaceae. Photograph by F. Gohier. National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.

South Africa, and is widely cultivated for its large, pink, bell-shaped flowers, which are moth-pollinated. The genus Hippeastrum, which is native to the West Indies, Mexico, and as far south as Argentina, has also been called Amaryllis by some taxonomists. Whatever its correct identity, many species of this genus have spectacular, large flowers that have evolved for pollination by birds, and are commonly grown as ornamentals.

Many members of the tribe Narcisseae are also widely cultivated, both indoors and outdoors. Most of the horticultural varieties originate from Spain, Portugal, or Morocco, and are small to medium-sized herbs, with linear leaves around a leafless stem that typically bears one to several flowers. The spring-flowering species have been most intensively bred as garden ornamentals, especially the common daffodil (Narcissus pseudonarcissus). Snowdrops (Galanthus nivalis), an early blooming ornamental, and St. John's lily (Crinum asiaticum), are also amaryllids. Clivia is a common houseplant, especially in Europe, that is prized for its deep-green, shiny leaves and its large salmon-colored flowers, and for the fact that it requires little light, water, or attention.

Agaves are often included in the amaryllis family. However, this taxonomic treatment is controversial, and agaves are sometimes put into their own family, the Agavaceae. About 300 species live in dry habitats from the southern United States to northern South America. These are conspicuous perennials, with a dense rosette of large, persistent sword-like leaves that bear spines at the tip, and often along the margins as well.

The scientific name Agave comes from the Greek agaue, which means noble, referring to the height of their flowering stalks. Their common name, century plant, refers to the long period of time that these plants remain in a non-sexual, vegetative state before flowering. This period generally lasts for 5-50 years, and not 100 years as the name implies. When they are ready to flower, Agave plants rapidly develop a thick flowering stem that may reach 20 ft (6 m) in height. Greenhouse keepers have sometimes come to work in the morning to find a flowering stem of an agave poking through the broken glass of their greenhouse. After this one episode of sexual activity, some species of agave plants die.

A few species of agaves are commercially important. Agave americana, commonly called American aloe or century plant, contains aloe, which is a commonly used ingredient in shampoos, moisturizers, and salves. Also important is the production of Mexico's national alcoholic beverage, pulque, which is mostly made from Agave americana, although a few other species of agave are also used. When the flowering stem is formed, a large amount of sap is produced. The bud at the end of the developing flowering stem is removed, and a cavity scooped out in which the sugary sap collects. As much as 238 gal (900 l) can be recovered from one plant over three to four months. The sap is fermented, resulting in a milky liquid with an alcohol concentration of 4-8 %. This beverage is pulque. A more potent liquor known as mescal is produced by distillation of pulque.

Many species of agave are valuable for the long fibers in their leaves. Aztecs used the fibers of henequen (A. fourcroydes) to make a twine, and the practice continues today. The stronger sisal hemp is derived from leaves of A. sisalana, native to the Americas but now grown in many parts of the tropics. Sisal is commonly used to manufacture baler twine for agriculture and a parcelling twine. The hard fibers of Furcraea macrophylla of Colombia have been used to make the large bags used for shipping coffee beans from that and other countries.

Resources

Books

The American Horticultural Society. The American Horticultural Society Encyclopedia of Plants and Flowers. New York: DK Publishing, 2002.

Heywood, Vernon H. ed. Flowering Plants of the World. New York: Oxford University Press, 1993.


Les C. Cwynar

KEY TERMS

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Raphide

—Needle-like crystals found within the cells of many plants, usually made of calcium oxalate.

Tepal

—Perianth parts that do not form distinct petals and sepals.

Xerophyte

—A plant adapted to dry or drought prone habitats.

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