1. Compositae (菊科)
2. Aster (紫菀属)
3. Aster hypoleucus (白背紫菀)

Shrubs, ca. 15 cm tall; stems fascicled. Stems numerous, densely branched; current-year branches simple or divaricately branched, erect, slender, strict, angled, white tomentose, densely leafy, terminal branches and peduncles hard and persistent by anthesis. Leaves suberect, shortly petiolate; blade adaxially dark green, elliptic or oblanceolate, 5-15 × 2-3.5 mm, leathery, abaxially white tomentose, adaxially arachnoid or glabrate, base attenuate, margin strongly revolute, entire or 1- or 2-serrate-spinose, apex acute or obtuse, spinose. Capitula 1-3 terminal on lateral branches; peduncles 2-3 cm; bracts minute, linear-lanceolate, membranous. Involucres campanulate, 4-5 mm in diam.; phyllaries 4-seriate, imbricate, subleathery, apex reddish purple; outer phyllaries lanceolate-ovate, short, apex acute; inner phyllaries linear-lanceolate, ca. 5 × 0.6 mm, 4-5 × as long as outer phyllaries, margin narrowly scarious, erose, villosulous-ciliate. Ray florets ca. 13, white when dry, tube ca. 2.2 mm, hairy, lamina ca. 4.5 × 1 mm; disk florets yellow, ca. 3.8 mm, tube 1-1.1 mm, limb narrowly funnelform, tube and limb base hairy, lobes lanceolate, ca. 1 mm, glabrous. Achenes tan, narrowly obovoid, slightly compressed, trigonous, ca. 1.6 mm (immature), silky, pale 3-ribbed. Pappus 3-seriate, whitish; outermost bristles ca. 0.5 mm; outer bristles slender, ca. 1.2 mm; inner bristles acute, 2.5-3.5 mm. Fl. Jul.

3000-3700 m. S Xizang (Zangbo valley).