TAMARICALES

the tamarisk order of dicotyledonous flowering plants comprising three families (Tamaricaceae, Frankeniaceae, and Fouquieriaceae) of trees, shrubs, and herbs usually found in temperate and subtropical steppes, deserts, and salt deserts and along the margins of salt lakes and seacoasts. The plants are characterized by radially symmetrical bisexual flowers with four to seven sepals, which persist in the mature fruit, and petals. The plant is also distinguished by a one-chambered ovary, which has several to many ovules that develop into seeds bearing a tuft of hairs at one end. The order is considered to be evolutionarily advanced and related to the willow order (Salicales), both of which are thought to have been derived from the violet order (Violales), probably from the family Flacourtiaceae of that order. The tamarisk family (Tamaricaceae) contains four genera: Tamarix, 54 species; Reaumuria, 20 species; Myricaria, 10 species; and Hololachna, 2 species. All but Reaumuria are large shrubs or small trees with minute flowers borne in dense, feathery inflorescences (clusters). Reaumuria is a small shrub with relatively large solitary flowers. The leaves of all tamarisks are alternately produced on the twigs but are so small, scalelike, and closely appressed that the stems look bare. The flowers have 4 to 10 stamens (male pollen-producing structures), a 3- or 4-parted style (the upper part of the female structure, which bears the pollen-receptive surfaces, or stigmas), and slightly fused sepals. Of horticultural interest are the false tamarisk (species Myricaria germanica); the Athel tree, or salt tree (Tamarix aphylla); and the salt cedar, or French tamarisk (T. gallica). The alkali-heath family (Frankeniaceae) has four or possibly five genera (Frankenia, 25 species; Anthobryum, 4 species; Niederleinia, 3 species; Hypericopsis, 1 species; and, questionably, Petrusia, 1 species). These are tropical and temperate, salt-tolerant herbs or softly woody shrubs with jointed stems, opposite leaves, and flowers having 4 to 10 stamens like those of the tamarisks but with only one style and free, unconnected sepals. The foliage is characteristic in that the leaves and twigs are in opposite pairs, each pair rotated at right angles on the stem relative to the pairs immediately above and below. Of horticultural interest are the alkali heath (Frankenia grandifolia) and several species of the same genus, which are cultivated as rock-garden novelties for their matlike growth forms, hairy, inrolled leaves, and small, pink or white flowers. Bright red tubular flowers of ocotillo (Fouquieria splendens) The candlewood family (Fouquieriaceae) contains two genera (Fouquieria, nine species; and Idria, one species) of thorny, small-leaved plants native to warm, dry regions of southwestern North America. The flowers differ technically from those of the other two families in having a tubular corolla (fused petals), 10 to 17 stamens with hairy filaments (basal parts), and three styles arising from a three-lobed ovary. The most notable plants of this family are the ocotillo, or coachwhip cactus (Fouquieria splendens; see photograph), and the boojum tree (Idria columnaris).