23. Spiraea rosthornii Pritzel ex Diels, Bot. Jahrb. Syst. 29: 383. 1900.
南川绣线菊 nan chuan xiu xian ju
Spiraea prattii C. K. Schneider.
Shrubs to 2 m tall. Branchlets spreading, yellow-brown turning gray-brown, pubescent when young, later glabrescent; buds long ovoid, nearly equaling petioles, with 2 scales, glabrous, apex acuminate. Petiole 5–7 mm, hairy; leaf blade abaxially gray-green, adaxially green, ovate-oblong to ovate-lanceolate, 2.5–5(–8) × 1–2(–3) cm, abaxially pubescent, more densely so on veins, adaxially pilose, base rounded to subtruncate, margin incised doubly serrate, apex acute or shortly acuminate. Corymbs terminal on lateral branchlets, compound, 6–10 × 7–11 cm, many flowered; rachis and pedicels pubescent; pedicels 5–7 mm; bracts ovate-lanceolate to linear-lanceolate, 5–8 mm, pubescent on both surfaces, base cuneate, margin with a few teeth, apex acute. Flowers 5–7 mm in diam. Hypanthium campanulate, ± pubescent abaxially. Sepals triangular, 1–2 mm, reflexed in fruit, apex acute. Petals white, ovate to suborbicular, 2–3.5 × 2–3 mm, glabrous, base shortly clawed, apex obtuse. Stamens ca. 20, longer than petals. Disk annular, 10-lobed; lobes broad, apex sometimes emarginate. Styles shorter than stamens. Follicles spreading, pubescent; styles terminal, divergent.
Slopes in mixed forests, stream sides; 1000--3500 m. Anhui, Gansu, Hebei, Henan, Qinghai, Shaanxi, Sichuan, Yunnan.