16. OLNEYA A. Gray.
A tree, with thin scaly bark, and stout terete hoary-canescent slightly angled branchlets armed with stout infrastipular spines. Leaves equally or unequally pinnate, hoary-canescent, persistent, 10—15-foliolulate, destitute of stipules and stipels, short-petiolate, often fascicled in earlier axils; leaflets oblong or obovate, entire, obtuse, often mucronate at apex, cuneate at base, rigid, short-petiolulate, reticulate-veined, with a broad conspicuous midrib. Flowers on stout pedicels rather longer than the calyx, in short axillary few-flowered hoary-canescent racemes, with acute minute bracts and bractlets deciduous before the expansion of the flowers; calyx hoary-canescent, the lobes ovate, obtuse, almost equal, the two upper lobes connate nearly throughout; disk cupuliform, adnate to the tube of the calyx; corolla papilionaceous; petals unguiculate, purple or violet, inserted on the disk; standard orbicular, deeply emarginate, reflexed, furnished at base of the blade with two infolded ear-shaped appendages covering 2 prominent callosites; wing-petals oblique, oblong, slightly auriculate at base of blade on the upper side, free, as long as the broad obtuse incurved keel-petals; stamens 10, the superior stamen free, filling the slit in the tube formed by the union of the others; filaments filiform; anthers of the same length, oblong, uniform; ovary sessile or slightly stipitate, pilose; style inflexed, bearded above the middle; stigma thick and fleshy, depressed-capitate; ovules numerous, suspended from the inner angle of the ovary, superposed. Legume oblique, compressed, glandular-hairy, light brown, 2-valved, often tipped with the remnants of the long persistent style, 1—5-seeded, the valves thick and coriaceous, becoming unequally and interruptedly convex at maturity. Seeds broad-ovoid, slightly angled on the ventral side, suspended by a short thick funicle, without albumen; seed-coat thin, membranaceous, bright chestnut-brown and lustrous; embryo filling the cavity of the seed; cotyledons thick and fleshy, accumbent on the short incurved radicle.
The genus is represented by a single species of southern Arizona, California, and northwestern Mexico.
Olneya is in memory of Stephen T. Olney (1812—1878), author of a catalogue of the plants of Rhode Island.
1. [Olneya tesota] A. Gray. Ironwood.
Leaves 1′—2½′ long, with leaflets ½′—¾′ in length, appearing in June and persistent until the following spring. Flowers unfolding with the leaves, nearly ½′ long. Fruit light brown, very glandular, fully grown at midsummer, ripening before the end of August, 2′—2½′ long.
A tree, sometimes 25°—30° high, with a short trunk occasionally 18′ in diameter and usually divided 4°—6° above the ground into a number of stout upright branches, and slender branchlets thickly coated at first with hoary-canescent pubescence disappearing early in their second year, and then pale green and more or less spotted and streaked with red, becoming pale brown in their third season, their spines straight or slightly curved, very sharp and rigid, ⅛′—¼′ long, and persistent at least during two years. Bark of the trunk thin, exfoliating in long longitudinal dark red-brown scales. Wood very heavy, hard and strong, although brittle, rich dark brown striped with red, with thin clear yellow sapwood; valued as fuel and sometimes manufactured into canes and other small objects.
Distribution. Sides of low depressions and arroyos in the desert; valley of the Colorado River south of the Mohave Mountains, California, to southwestern Arizona, and to Sonora and Lower California; most abundant and of its largest size in Sonora.