Lily Family (Liliaceae)
Lilies are the classic representatives of the monocotyledons—those plants with only one seed leaf. Lilies are mostly perennial, erect herbs arising from a bulb. Some climb, a few are woody, but most arise from underground stems or other structures. The leaves vary in number from one to many, and are arranged on the stem alternately or in whorls. The leaves are flat, linear to lance-shaped, without teeth along the margins, often widen into a papery sheath where they attach to the stem, lack stalks, and are typically parallel veined.
Some species of lilies are famous for their magnificent flowers, which are often trumpet or funnel shaped, nodding, and heavily scented. Lily flowers are bisexual, radially symmetrical, and their parts are usually in some multiple of three (four in Maianthemum), with no distinction in the appearance of petals and sepals. There are usually six main segments to the showy part of the flower, which are attached to the base of the ovary. Flowers may occur singly at the top of a leafless stem (tulip), as several flowers arranged on a spike (as in lily-of-the-valley, Convallaria majalis), or in various other arrangements of many flowers, including the umbels of onions (Allium spp.). Lily flowers are insect pollinated. The fruits of lilies are either capsules or berries. The capsules are divided into three compartments, which contain many flat, round seeds that are often stacked like coins.
There are about 240 genera and 4,000 species in the Liliaceae. Lilies are a diverse group and recent taxonomists have tended to split the group into four main families: Liliaceae, the lilies proper; Convallariaceae, lily-ofthe-valley and Solomon's seals; Melanthaceae, or bunch-flowers; and Smilaceae, the catbriers or greenbriers. In this article, the Liliaceae is considered in the broadest sense, including all of these four groups.
Lilies are widely distributed, primarily in the Northern Hemisphere, with a major center of distribution in
the southwest and from Himalayan Asia to China, where they commonly are spring-flowering plants of steppes and mountain meadows. In North America, many familiar woodland plants of the springtime are members of the lily family, such as the trilliums and wake-robins of the genus Trillium, bellworts or merrybells (Uvularia), dogtooth violets (Erithronium) with their characteristic mottled brown leaves, wild lily-of-the-valley (Maianthemum canadense), and Solomon's seals (Polygonatum). Species of Smilax, which are mostly perennial herbs or shrubs occurring in tropical and subtropical regions, also occur in North America. Smilaxes are unusual among the monocotyledonous plants in producing tendrils, which are slender twining structures, used to climb and hold onto other plants.
Lilies are highly prized as house and garden ornamentals, and many of the most beautiful of these belong to the genus Lilium, the namesake of the family. Lilies have long held a fascination for people. The Madonna lily (L. candidum), which is native to the region of Greece to Syria, was depicted by early civilizations on pottery and mosaics. The most commonly grown greenhouse lily is the Easter or trumpet lily (L. longiflorum). Lilies have long been associated with Easter. During the Renaissance, European painters used white lilies to symbolize the Annunciation of the Virgin, that is, the announcement by the angel Gabriel to Mary that she would conceive a Son. The uniform, bright white color of many lilies symbolizes purity in some cultures. However, lilies also come in a variety of other colors. Flowers are purple in L. martagon of central Europe to China, yellow in L. canadense of eastern North America and L. croceum of central to southern Europe, orange in L. japonicum of Japan and L. tigrinum of east Asia, and rose in L. pardinarium. Many lilies have enchanting fragrances that are sometimes extracted for use in perfumes.
Tulips are also members of the lily family, in its broadest sense. Tulips are native to the Northern Hemisphere, with the greatest diversity of species occurring in the western and central parts of Asia. The name tulip derives from a Turkish word for turban, referring to the shape of the flower. Most horticultural varieties descend primarily from multiple crosses between two species, Tulipa gesneriana and T. suaveolens of western Asia. These are usually sold under the name T. gesneriana, although other species are increasingly involved in the development of new varieties.
The Turks were the first to cultivate the tulip and they introduced it into Europe, exactly when is not known, although the first reference to the tulip in a European publication was made in 1559. Tulips gradually increased in popularity until the early seventeenth century, when tulip mania swept Holland. There was a hysterical rush to raise and breed new and rarer varieties of tulips. Speculators invested the equivalent of thousands of dollars for a single bulb, and some people sold their houses to invest in the tulip market. In 1630 one bulb of a rare variety sold for the equivalent of $10,000. Tulip mania reached its peak between 1634-1637, forcing the Dutch government to step in and regulate the industry. The Netherlands remains the single largest producer of tulip bulbs, although Japan and the state of Washington are now important producers.
The economically important genus Allium is widely cultivated for its strong odor and flavor. Plants are characterized by a bulb, that is actually a giant bud surrounding a short stem. The leaves of the bud are extremely fleshy and tightly overlapping. The concentric lines seen in an onion cut crosswise are the margins of fleshy leaves. The outermost leaves are not fleshy but papery, forming the skin of the onion. Various members of this genus are cultivated: the common onion (A. cepa), garlic (A. sativum), leeks (A. porum), shallots (A. ascalonicum), and chives (A. schoenoprasum). Texas, New York, and California are the major onion producing regions in North America.
A number of other members of the lily family are of economic importance for a variety of reasons. A large number of lilies other than those described above are also important ornamentals. Fritallarias are popular ornamentals, with few to many leaves arranged either alternately or in whorls on the stem, and large, showy, bell-like flowers that are usually nodding. Many species of Fritallaria are of ornamental interest because the flowers are one basic color, checkered with another color. Fritallaria meleagris from central and southern Europe is purplish with white checkering, and F. aurea from Turkey is yellow and checkered. In the wild, many of the fritillarias appear to be pollinated by queen wasps.
Lily-of-the-valley is a small perennial native of Europe, that has become naturalized in parts of eastern North America, and is frequently planted for its beautifully scented spike of flowers that are commonly used in wedding bouquets and for perfumes. Other commonly grown ornamental lilies are hyacinths, grape hyacinths, and scillas.
The young shoots of asparagus (Asparagus officinalis) are an important cash crop, and A. plumosus is the asparagus fern (though not a fern) used by florists as lacy greenery in bouquets.
Wild sarsaparilla (Avalia nudicaulis) has long been an ingredient of soft drinks. Aloe (Aloe vera) once provided needles for early phonographs and remains important today as a salve in the treatment of burns and in cosmetics. Meadow saffron or fall crocus (Colchicum autumnale) was used to treat gout (a painful disease of inflamed joints), and is still much used in research. Cochicine is extracted from the plant and used to prevent spindle formation during mitosis, so that replicated chromosomes do not split apart. This produces a polyploid, that is, a double (or more) of the normal chromosome number.
Dragon's blood, the resin of Dracaena, the dragon tree, was once collected and used as a finish for the great Italian violins of the eighteenth century.
Many lilies are poisonous. Lily-of-the-valley is mildly poisonous, enough to be on the United States list of poisonous plants. Death camases (Zygadenus spp.) are extremely poisononous species. Zygadenus elegans is an attractive plant with a wand-like cluster of star-shaped flowers. It has an onion-like bulb, that unfortunately resembles the bulb of edible camases, which are in the genus Camassia. Zagadenus venenosus is a common cause of cattle poisoning in the western United States. Lilies known as squills are also quite toxic; the red bulbs of Urginea maritima are a valuable heart stimulant, but the white bulbs have been used as rodent killers. Scilla, another squill, also contains glucosides that have been used as rodenticides. Some greenhouse workers who handle tulips develop a severe dermatitis called tulip finger, which causes reddening and swelling of the finger in association with itchy and burning sensations, and in the worst cases results in scaly, eczematous skin.
Dahlgren, R.M.T., H.T. Clifford, and P.F. Yeo. The Families of the Monocotyledons: Structure, Evolution, and Taxonomy. Berlin: Springer-Verlag, 1985.
Taylor, N. Taylor's Encyclopedia of Gardening. 4th ed. New York: Houghton Mifflin, 1961.
Les C. Cwynar
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