Three species of Washingtonia are known: one inhabits the interior dry region of southern California and the adjacent parts of Lower California, and the others the mountain cañons of western Sonora and southern Lower California.
The genus is named for George Washington.
1. Washingtonia filamentosa O. Kuntze. Desert Palm. Fan Palm.
Leaves 5°—6° long and 4°—5° wide, light green, slightly tomentose on the folds; petioles 4°—6° long and about 2′ broad at apex, with sheaths 16′—18′ long and 12′—14′ wide, and ligules 4′ long and cut irregularly into long narrow lobes. Flowers: spadix 10°—12° long, 3 or 4 being produced each year from the axils of upper leaves, the outer spathe inclosing the bud, narrow, elongated, and glabrous, those of the secondary branches coriaceous, yellow tinged with brown, and laciniate at apex; flowers slightly fragrant, opening late in May or early in June. Fruit produced in great profusion, ripening in September, ⅓′ long; seed ¼′ long, ⅛′ thick.
A tree, occasionally 75° high, with a trunk sometimes 50°—60° tall and 2°—3° in diameter, covered with a thick light red-brown scaly rind and clothed with a thick thatch of dead pendant leaves descending in a regular cone from the broad crown of living leaves sometimes nearly to the ground. Wood light and soft, with numerous conspicuous dark orange-colored fibro-vascular bundles. The fruit is gathered and used as food by the Indians.
Distribution. Often forming extensive groves or small isolated clumps in wet usually alkali soil in depressions along the northern and northwestern margins of the Colorado Desert in southern California, sometimes extending for several miles up the cañons of the San Bernardino and San Jacinto mountains; and in Lower California.
Now largely cultivated in southern California, New Orleans, southern Europe, and other temperate regions.
Trees, with tall slender often clustered stems clothed for many years with the sheathing bases of the petioles of fallen leaves. Leaves suborbicular, divided into numerous two-parted segments plicately folded at the base; rachis short, acute; ligule thin, concave, furnished with a broad membranaceous dark red-brown deciduous border; petioles slender, flat or slightly concave on the upper side, rounded and ridged on the lower side, with a broad high rounded ridge, thickened and cartilaginous on the margins, more or less furnished with stout or slender flattened teeth; vagina thin and firm, bright mahogany red, lustrous, closely infolding the stem, its fibres thin and tough. Spadix paniculate, interpetiolar, its rachis slender, compressed, ultimate branches, numerous, slender, elongated, gracefully drooping, hoary-tomentose, the primary branches flattened, the secondary terete in the axils of ovate acute chestnut-brown bracts; spathes flattened, thick and firm, deeply two-cleft and furnished at apex with a red-brown membranaceous border, inclosing the rachis of the panicle, each primary branch with its spathe and the node of the rachis below it inclosed in a separate spathe, the whole surrounded by the larger spathe of the node next below. Flowers perfect, minute, sessile on the ultimate branches of the spadix, in the axils of ovate acute chestnut-brown caducous bracts, solitary toward the end of the branches and in two- or three-flowered clusters near their base; calyx truncate at base, divided into three broadly ovate sepals dentate on the margins, valvate in æstivation, enlarged and persistent under the fruit; corolla three-parted nearly to the base, its divisions valvate in æstivation, oblong-ovate, thick, concave and thickened at apex, deciduous; stamens six, included; filaments nearly triangular, united below into a cup adnate to the short tube of the corolla; anthers short-oblong, attached on the back below the middle, introrse, two-celled, the cells opening longitudinally; ovary obovoid, of three carpels, each with two deep depressions on their outer face, united into a slender style; stigma minute, terminal, persistent on the fruit; ovule solitary, erect from the bottom of the cell, anatropous. Fruit drupaceous, subglobose, one-seeded, black and lustrous; exocarp thin and fleshy; endocarp thin, crustaceous; seed erect, free, subglobose, light chestnut-brown; testa thin and hard; hilum small, suborbicular; raphe ventral, oblong, elongated, black, slightly prominent, without ramifications; embryo lateral; albumen homogeneous.