ARALES

order of monocotyledonous flowering plants comprising the families Araceae and Lemnaceae. The order includes herbs, climbing shrubs, marsh plants, and floating aquatic forms, most of which live in the tropics. The Arales may share common evolutionary ancestors with the palm order (Arecales) and the Panama hat palm order (Cyclanthales) from the immediate ancestors of the lily order (Liliales). Arales is rich in popular ornamentals and foliage plants, all in the arum, or aroid, family (Araceae). The duckweed family (Lemnaceae) is remarkable for containing the smallest known flowering plants. The species may be terrestrial, aquatic, or epiphytic. Some are herbaceous and stemless, with few arrow-shaped leaves arising from a rootstock. Others are climbers, clinging by aerial roots to tree trunks and other upright supports and unfurling large, sometimes dissected, leaves alternately along the stem, with each leaf bearing a temporary, almost colourless sheath at the base of the leaf stalk (petiole). The inflorescence, adapted to insect pollination, is formed of a single spike, or spadix, on which few-to-many minute-to-small flowers are arranged, the entire structure being enveloped by a sometimes colourful floral leaf, or spathe. The spadix often emits a fetid odour that attracts flies, which are trapped for a time and then escape to pollinate other plants. The fruit may be a brightly coloured berry (sometimes many, clustered on the spadix); rarely it is dry and leathery, rupturing to release seed. The sap often contains calcium oxalate crystals, which upon ingestion can numb the tongue and throat. The Araceae has about 115 genera and 2,000 species, native primarily to the tropics and subtropics. The few temperate zone species are widely distributed, especially in wet habitats. The family is known for several wildings and many greenhouse and foliage ornamentals. The largest genera in the family Araceae are Anthurium (600 species); Philodendron (275 species); Arisaema (150 species), which is believed to be pollinated by snails; Homalomena (140 species); Rhaphidophora (100 species); Amorphophallus (100 species), some species of which produce inflorescences up to 1 m (about 40 inches) tall; Pothos (75 species); and Alocasia (70 species). The genera Philodendron and Monstera are grown for their vinelike habit and large, green leaves. The elephant's ear (Colocasia esculenta) is a variable species that includes the dasheen, taro, and eddo of the tropics; these plants are grown for their large edible corms, or bulblike underground stems. The florist's calla lily is Zantedeschia aethiopica, and the genus Calla includes the water arum (C. palustris); both are grown ornamentally. Species of dumb cane (Dieffenbachia) are popular indoor foliage plants that can cause inflammation and swelling of the throat if a piece of stem is chewed. Jack-in-the-pulpit (Arisaema triphyllum) is a well-known woodland plant. The golden club (Orontium aquaticum) is occasionally cultivated in ponds or greenhouse pools for its bright yellow spadices. Water lettuce, or water cabbage (Pistia stratiotes), is an edible and attractive floating ornamental. Amorphophallus includes several curiosities grown for their large and ill-smelling inflorescences. Sweet flag rhizome, or calamus root (Acorus calamus), contains a spicy, aromatic oil often used in medicines and flavourings. Eastern skunk cabbage (Symplocarpus foetidus) is a well-known marsh plant with a fetid odour. The lords-and-ladies, or cuckoopint (Arum maculatum), is one of the few arums found as far north as Europe. Several species of Spathiphyllum are grown as indoor potted plants. Another beautiful foliage plant is Caladium, available in many horticultural varieties with large, colourful leaves. The Lemnaceae, with 6 genera and 30 species of minute floating aquatic forms, is widespread in the temperate and tropic zones. The family is remarkable for the smallest known flowering plants, the duckweeds (Lemna species) and watermeals (Wolffia species). Certain of these green, leaflike, flattened species, with or without rootlets and only a few millimetres across, are used in aquariums and pools as ornamentals or as food for waterfowl and fish. Flowers, rarely produced, bear only the essential organs, no sepals or petals: the male flower has one or two stamens and the female a single pistil. The plants reproduce primarily by basal division.