刺槐族 ci huai zu
Sun Hang (孙航); Bruce Bartholomew
Trees, shrubs, or herbs, sometimes with glandular trichomes. Stipules narrow, sometimes becoming thorns or absent. Leaves pulvinate, even- or odd-pinnate; leaflets opposite or subopposite; stipels often present. Racemes all axillary or sometimes fasciculate at older nodes, pendulous; bracts membranous, caducous. Calyx campanulate, sometimes bilabiate, 5-toothed with adaxial 2 teeth ± connate. Standard often with basal appendages; wings free from keel, often with corrugated venation. Stamens 9+1, diadelphous, vexillary filament free or connate with others higher up into an open sheath or rarely forming a closed tube; anthers uniform or nearly so. Ovary stipitate; ovules many to several ovuled, rarely only 1 or 2. Legume woody to thinly leathery, 2-valved, continuous within or rarely septate between seeds. Seeds broadly ovoid, oblong-reniform, or oblong, flat, without strophiole.
Eleven genera and ca. 72 species: distributed in America, especially in C and W South America; one genus and two species cultivated in China.
刺槐属 ci huai shu
Trees or shrubs, all parts (excluded corolla) sometimes with glandular bristles. Buds only axillary. Stipules bristlelike spinelike. Leaves odd-pinnate; leaflets blades petiolulate and stipellate, margin entire margins. Racemes axillary, pendulous; bracts membranous, caducous. Calyx campanulate, 5-lobes, adaxially 2 lobes subconnate into an apical lip. Corolla white, pink or rosy. Petal stipitate; standard large, retroflexed; wings curved; keel incurved, blunt. Stamens diadelphous, single one distinct from other 9 connate ones; anthers homomorphic, 2-loculed longitudinal dehiscent. Ovary stipitate, many ovuled. Style subulate, apically piliferous; stigma small, terminal. Legume compressed, narrowly winged along ventral suture, segments often with appressed bristles. Seeds oblong or obliquely reniform, strophiole absent.
About four to ten species: North America and Central America; two species (cultivated) in China.
1a. Branchlets, rachis and pedicel with appressed adnate puberulence; stipulate spines present; leaflets oblong; corolla white; legume smooth ............................................................... 1. R. pseudoacacia
1b. Branchlets, rachis and pedicel with appressed spiny hairs or piloglandulose; stipulate spine absent; leaflets oblong to suborbicular; corolla rosy; legume scabrous piloglandulose .............. 2. R. hispida
刺槐 ci huai
Robinia pseudoacacia var. inermis de Candolle; R. pseudoacacia var. pyramidalis (Pepin) C. K. Schneider; R. pseudoacacia var. umbraculifera de Candolle; R. pyramidalis Pepin.
Trees, 10–25 m tall, deciduous. Bark gray-brown to dark brown, longitudinally fissured, rarely smooth. Branchlets gray-brown, with faintly hairs, glabrescent; stipulate spine, up to 2 cm; winter bud small, with hairs. Leaves 10–25(–40) cm; rachis adaxially groove; petiolule 1–3 mm; stipel acicular; leaflets 2–12 pairs, usually opposite or subopposite; leaflet blades elliptic, oblong, or ovate, 2–5 × 1.5–2.2 cm, abaxially grayish green and with appressed pubescence when young but glabrescent, adaxially green, base rounded to broadly cuneate, margin entire, apex rounded, retuse, and apiculate. Racemes axillary, 10–20 cm, pendulous, many flowered, fragrant; bracts caducous. Pedicel 7–8 mm. Calyx obliquely campanulate, 7–9 mm; teeth 5, triangular to ovate-triangular, densely appressed pubescence. Corolla white, stipitate; standard suborbicular, ca. 1.6 × 1.9 cm, retroflexed, inside with yellow spots, base rounded, apex with a sinus; wings obliquely obovate, subequal to standard, ca. 16 mm, one lateral auriculate rounded; keel falcate, triangular, equal to wings or slightly short, connate at leading edge, obtuse. Stamens diadelphous, one opposite to standard free. Ovary linear, ca. 1.2 cm, glabrous; stalk 2–3 mm. Style subulate, ca. 8 mm, apically curved, apex piliferous; stigma terminal. Legume brown or with reddish-brown stripes, linear-oblong, 5–12 × 1–1.3(–1.7) cm, compressed, apex volute and mucronate, podogyne short, narrow wings along ventral suture; calyx persistent, 2–15-seeded. Seeds brown to dark brown, slightly glossy, sometimes with stripes, subreniform, 5–6 × ca. 3 mm; hilum rounded, oblique to one end. Fl. Apr–Jun, fr. Aug–Sep. 2n = 20, 22.
Cultivated in all of China except Hainan and Xizang [native to E North America].
Cultivated and sometimes naturalized in many parts of the world.
毛洋槐 mao yang huai
Shrubs, 1–3 m tall, deciduous. Young branch green, densely appressed amaranthine and scabrous piloglandulose and white pilose; biennial branches dark gray-brown, densely brown bristles, 2–5 mm. Leaves 15–30 cm; rachis appressed bristle and white curled pubescence, adaxially grooved; petiolule appressed white pubescence; stipel aristiform, persistent; leaflets 5–7(–8) pairs; leaflet blades elliptic, ovate, broadly ovate, or suborbicular, 1.8–5 × 1.5–3.5 cm, often smallest pair leaflets basally on rachis lower, base rounded, rounded, apex rounded and aristiform, glabrous, abaxially grayish green, adaxially dark red when young but later turned into green, midvein abaxially with sparse appressed trichomes. Racemes axillary, all but corolla appressed purple piloglandulose and white pubescence, 3–8-flowered; peduncle 4–8.5 cm; bracts ovate-lanceolate, 5–6 mm, caducous, sometimes apical ones 3-lobed, apex gradually caudate. Calyx purple, obliquely campanulate; tube ca. 5 mm; calyx teeth triangular, 3–6 mm, apex caudate to subulate. Corolla red to rosy. Petals stipitate; standard subreniform, ca. 2 × 3 cm, apex with a sinus; wings falcate, ca. 2 cm, auriculate; keel nearly triangular, ca. 1.5 cm, apex rounded, connate at leading edge, auriculate. Stamens diadelphous, one opposite to standard free; anthers elliptic. Ovary subterete, ca. 1.5 cm, with densely appressed adenose papillae, faintly pilose along sutures, many ovuled. Stigma terminal. Legume linear, 5–8 × 8–12 mm wide, compressed, 3–5-seeded, with dense appressed bristles, podogyne short, apex acute. Fl. May–Jun, fr. Jul–Oct.
Cultivated in at least Anhui, Hebei, Henan, Shaanxi, Shandong, Shanxi, and Zhejiang [native to C and E North America].
Grown as an ornamental.