Homostylium hypoleucum Z. X. Fu. A. Habit 2025, comb. nov.

4.Homostylium hypoleucum(Hand. - Mazz.) Z. X. Fu comb. nov. Figs 9, 10, 11 ≡ Aster hypoleucus Hand. - Mazz., J. Bot. 76: 285. 1938. ≡ Sinosidus hypoleucus (Hand. - Mazz.) G. L. Nesom, Phytoneuron 2020-64: 13. 2020. Type: China, Xizang, Nangxian, Kyimdong Dzong, F. Kingdon-Ward 11993 (holotype, BM 000945771!) (Suppl. material 1: fig. S 30). Type. China • Xizang, Nangxian, Kyimdong Dzong, F. Kingdon-Ward 11993 (holotype, BM 000945771!) (Suppl. material 1: fig. S 30). Description. Dwarf shrubs, cespitose, 12–36 cm tall. Leaves alternate, elliptic to oblanceolate, 0.3–1.7 × 0.19–0.33 cm, leathery, margins entire or (1 -) 2 - serrate-spinose, strongly revolute, adaxially dark green, glabrate, arachnoid, or sparsely sericeous, abaxially densely white tomentose. Capitula 1–3, terminal on lateral branches. Peduncles 1.5–3 cm long, sparsely strigose, with few subulate bracteoles. Involucres subcampanulate, 4–5 mm in diameter. Phyllaries 4 - seriate, imbricate, outer phyllaries extremely short, ovate-lanceolate, inner phyllaries linear-lanceolate, 5 × 0.6 mm, 4–5 × as long as outer phyllaries. Distribution. Endemic to China, SE Xizang (Lang, Gyaca, Mainling, and Zangbo Valley) (Fig. 10). Habitat. Arid mountain slopes of river valleys, rock crevices, woodland margins, and shrublands. 3000–3700 m. Phenology. Flowering July to August. Fruiting August to September. Etymology. The specific epithet “ hypoleucum ” is derived from the Greek “ hypo - ”, meaning “ under ” or “ beneath ”, and “ leucos ”, meaning “ white ”, combined with the Latin neuter suffix “ - um ”. The name likely refers to the whitish coloration on the abaxial surface of the leaves (abaxially densely covered with thick white tomentum) in this species. Specimens examined. China • Xizang: Gyaca, B. Q. Xu et al. XiaNh – 07 zx – 0639 (IBSC), Z. C. Ni et al. 2724 (PE 01836991, PE 01836993, PE 01836992), Qinghai – Xizang Supplement Team 750652 (PE 00275826, PE 00275825), Xizang Med. Herb Exped. 4399 (PE 01532326, PE 00275824); Nangxian, Z. X. Fu 1475 (PE), 1476 (PE), 1477 (PE), 1478 (PE), 1479 (PE), Qinghai – Xizang Exped. 7899 (PE 01532325, PE 01532063), Qinghai – Xizang Veget. Exped. 3314 (PE 01836952, PE 01532324), H. N. Qin et al. 554 (PE), J. Luo et al. L 048 (QTPMB), Xizang Med. Herb Exped. 4250 (PE 00275828, PE 00275828), Z. C. Ni et al. 2757 (PE), F. Kingdon-Ward 11993 (BM 000945771); Mainling, Xizang Med. Herb Exped. 4302 (PE 01532328, PE 00275827). Notes. This species can be easily distinguished from other shrubby Homostylium by its dwarf shrub habit and the persistent peduncles. Its leaf shape is similar to that of H. lavandulifolium. However, H. hypoleucum has relatively shorter and smaller leaves without adaxial papillate protrusions, capitula not arranged in a dense corymbose, broader involucres, and white pappus, which are diagnostic characters.