YUCCÆ.
Leaves, alternate, linear-lanceolate. Flowers in terminal panicles; sepals and petals nearly similar, subequal, withering-persistent; ovary with more or less deeply introduced dorsal partitions; ovules numerous, 2-ranked in each cell; embryo subulate, obliquely placed across the seed; cotyledon arched in germination.
Yuccæ as here limited consists of two American genera, Hesperaloe, with two species, low plants of Texas and Mexico, and Yucca.
1. YUCCA L.
Trees with simple or branched stems prolonged by axillary naked buds, dark thick corky bark, light fibrous wood in concentric layers, and large stout horizontal roots; or often stemless. Leaves involute in the bud, at first erect, usually becoming reflexed, abruptly narrowed above the broad thickened clasping base, usually widest near the middle, concave on the upper surface, involute toward the horny usually sharp-pointed apex, convex and often slightly keeled toward the base on the lower surface, the margins serrulate or filamentose, light or dull green. Flowers fertilized by insects and opening for a single night, on slender pedicels in 2 or 3-flowered clusters or singly at the base of the large compound panicle furnished with conspicuous leathery white or slightly colored bracts, those at the base of the pedicels thin and scarious; perianth cup-shaped, with thick ovate-lanceolate creamy white segments more or less united at base, usually furnished with small tufts of white hairs at the apex, those of the outer rank narrower, shorter, and more colored than the more delicate petal-like segments of the inner rank; stamens 6, in 2 series, free, shorter than the ovary (as long in 1), white, with club-shaped fleshy filaments, obtuse and slightly 3-lobed at the apex, and cordate emarginate anthers attached on the back, the cells opening longitudinally, curling backward and expelling the large globose powdery pollen-grains; ovary oblong, 6-sided, sessile or stalked, with nectar-glands within the partitions, dull greenish white, 3-celled, gradually narrowed into a short or elongated 3-lobed ivory-white style forming a triangular stigmatic tube. Fruit oblong or oval, more or less distinctly 6-angled, 6-celled, usually beaked at the apex, baccate and indehiscent or capsular and 3-valved, the valves finally separating at the apex; pericarp of 2 coats, the outer at maturity thick, succulent and juicy, thin, dry and leathery, or thin and woody. Seeds compressed, triangular, obovoid, or obliquely ovoid or orbicular, thick, with a narrow 2-edged rim, or thin, with a wide or narrow brittle margin; seed-coat thin, black, slightly rugose or smooth; embryo in plain or rarely ruminate hard farinaceous oily albumen; cotyledon much longer than the short radicle turned toward the small oblong white hilum.
Yucca is confined to the New World and is distributed from Bermuda and the eastern Antilles, through the south Atlantic and Gulf states to Oklahoma and Arkansas, and through New Mexico and northward along the eastern base of the Rocky Mountains to South Dakota, westward to middle California, and southward through Arizona, Mexico, and Lower California to Central America. About thirty species with many varieties and probable hybrids are recognized. Of the species which inhabit the territory of the United States nine assume the habit and attain the size of small trees. The root-stalks of Yucca are used as a substitute for soap, and ropes, baskets, and mats are made from the tough fibres of the leaves. Many of the species are cultivated, especially in countries of scanty rainfall, for their great clusters of beautiful flowers, or in hedges to protect gardens from cattle.
The generic name is from the Carib name of the root of the Cassava.
CONSPECTUS OF THE ARBORESCENT SPECIES OF THE UNITED STATES.
Flower-clusters usually sessile, or short-stalked. Fruit pendulous, with thick succulent flesh; seeds thick; albumen ruminate. Segments of the perianth slightly united at the base. Panicle glabrous or puberulous. Ovary stipitate; leaves sharply toothed on their horny margins, smooth, dark green, slightly concave.1. [Y. aloifolia] (C). Ovary sessile. Leaves concave, blue-green, rough on the lower surface.2. [Y. Treculeana] (E). Leaves concave above the middle, light yellow-green, smooth. Style elongated.3. [Y. macrocarpa] (E, H). Style short.4. [Y. mohavensis] (G, H). Panicle coated with hoary tomentum; leaves concave, smooth, light yellow-green.5. [Y. Schottii] (H). Segments of the perianth united below into a narrow tube; leaves flat, smooth, dark green.6. [Y. Faxoniana] (E). Fruit erect or spreading, the flesh becoming thin and dry at maturity; seeds thin; albumen entire. Leaves rigid, concave above the middle, blue-green, sharply serrate.7. [Y. brevifolia] (F, G). Leaves thin, flat or concave toward the apex, nearly entire, rough on the lower surface, dull or glaucous green.8. [Y. gloriosa] (C). Flower-clusters long-stalked; fruit capsular, erect, finally splitting between the carpels and through their backs at the apex; seeds thin; albumen entire; leaves thin, flat, filamentose on the margins, smooth, pale yellow-green.9. [Y. elata] (E, H).