GERANIALES

the diverse geranium order of flowering plants, belonging to the class Magnoliopsida (dicotyledons; characterized by two seed leaves). It consists of 5 families and some 3,600 species. Most members of the order are herbaceous, with a superior compound ovary and one to two ovules per locule. Many of the economically important families of Geraniales require rich, moist soil. The wood-sorrel family (Oxalidaceae) is composed of some 900 species readily recognized by their three cloverleaf-like leaflets. Most of the Oxalidaceae are herbs found in tropical regions; some are weeds in temperate regions, and still others are grown as ornamentals. The geranium family (Geraniaceae), consisting of 14 genera and some 700 species, is worldwide in distribution and generally grows in temperate or subtropical regions. The florist's geranium ( Pelargonium domesticum) is a favourite house plant and is available in many varieties. These cultivars (horticultural varieties) have originated from plants native to South Africa. Herb Robert (Geranium robertianum) is a well-known garden plant, as are some species of Erodium. The pin-clover (E. cicutarium), a Mediterranean species now naturalized in the United States, is a weed, but in California it is grown as a forage crop. Geranium oil, used in perfumes, is produced by Pelargonium odoratissimum and related species. The remaining families of the Geraniales order are of lesser economic importance; some are, however, important locally for food and ornamental plantings, and many are of scientific interest. The family Balsaminaceae has 2 genera and some 900 species of subsucculent annual or perennial plants. Some species of Impatiens are cultivated. Nasturtiums of the Tropaeolaceae, which are garden plants suited to moist habitats, yield spicy buds containing mustard oil for seasoning. Of the nearly 100 species in this genus, Tropaeolum tuberosum of the high Andes is an important vegetable-tuber crop. Limnanthaceae has 2 genera and 8 species of small, subsucculent annual plants, found in temperate parts of North America. Some species of Limnanthes are used as ornamentals, and they have attracted interest as a source of oilseeds. Many members of the Oxalis genus propagate vegetatively. Reproduction by seeds is, however, the universal method of perpetuating the species of this order. Inflorescences of the Geraniales range from those set closely on an elongated flowering stalk (spike) to branched clusters (panicles). A few flat-topped flower clusters (umbels) are produced in the wood-sorrel and balsam families. A representative flower of the Geraniales possesses five sepals and an equal number of petals of similar size and shape, 10 stamens in two whorls, and a pistil composed of five carpels. Sepals are joined basally to form a short funnel; petals are separate, and stamens are joined at their base. The ovary portion of the pistil consists of five chambers, each containing one ovule. Five separate styles end in pollen-receptive stigmas. Insects are the almost universal agents of Geraniales pollination. The fragrant flowers of the garden geranium are visited by nocturnal insects. Some North American species of Impatiens are pollinated by hummingbirds. After pollination and fertilization, the ovule becomes the seed and the ovary the fruit. In some families, the fruit ripens dry and splits at maturity into segments (mericarps), or, in other species, the fruits open completely (capsule).