Styrax chrysocarpus H.L. Li (1944: 312)

Zhang, Rui, Zhao, Wan-Yi, Liu, Yu-Lin, Fan, Yu & Tang, Ming, 2021, Rediscovery of Styrax buchananii and S. chrysocarpus, with supplemental descriptions adding fruit and floral characters, respectively, Phytotaxa 479 (2), pp. 173-182 : 179-181

Styrax chrysocarpus H.L. Li (1944: 312) . Figs. 1B , 2B, D , 5–6 .

TYPE:— China. Yunnan, Pingbian Miao Autonomous County, 1400 m, 9 July 1934 , H. T. Tsai 62505 (holotype, A00018412 !; isotypes, IBSC0454257 !, KUN, LBG00098686 !, NAS00072204 !, PE00027899 !) .

Trees 6–13 m tall. Young branchlets yellow-brown-stellate-tomentose; older branchlets dark brown, subglabrous. Petiole 5–10 mm long, densely yellow-gray-stellate-pubescent. Lamina 6–21 × 3.5–12 cm, chartaceous, oblongovate to oblong, base rounded or broadly cuneate, apex acute to slightly acuminate; adaxially sparsely yellow-graystellate-pubescent and abaxially densely yellow-gray-stellate-hirsute, prevalent on veins; margin subentire or remotely irregular serrulate apically; secondary veins 5 to 8 on each side of midvein, adaxially plane or slightly sunken, abaxially prominent; tertiary veins reticulate, parallel and perpendicular to secondaries, abaxially prominent. Fertile shoots 10–20 cm long, 3- or 4-leaved. Inflorescences arising from shoots of current growing season; lateral inflorescences racemose, 2–5 cm long, 2- to 5-flowered, often with 1 or 2 flowers occurring in same leaf axil; pseudoterminal inflorescences usually paniculate, sometimes racemose, 4–11 cm long, 4- to 10-flowered, lateral branches 0 to 3, sometimes with 2 or 5 short lateral racemes from base of inflorescence, rachis and branches densely yellowstellate-pubescent. Pedicel (3–) 4–7 mm long, densely yellow-stellate-hirsute; bracteoles ca. 2 mm long, linear, usually positioned at base of pedicels. Flowers 1.5–1.7 cm long. Calyx 4–5 × 4–5 mm, cupuliform, swollen at base, adaxially yellowish-white-appressedpubescent with 2- or 3-armed or stellate trichomes, somewhat scarious, brown when dry, margin truncate, undulate, or irregularly lobed, teeth minute and not contiguous if present. Corolla 1.1–1.4 cm long, white, tube ca. 3 mm long, glabrous, lobes 5(6), 10–12 × 4–5 mm, lanceolate or ovate-lanceolate, stellate-tomentose on both sides. Stamens 10, rarely 12; filaments ca. 5 mm long, straight, distally attenuate, densely white- to yellow-stellate-hirsute throughout; anthers ca. 5 mm long, wider than distal portion of filament; connectives densely stellate-hirsute. Style densely white- stellate-hirsute from base to middle, upper subglabrous; stigma 0.2–0.3 mm wide, punctiform. Infructescences arising from shoots of current growing season, 1- to 5-fruited, yellow-stellate-tomentose. Fruiting pedicel 4–5 mm long. Fruiting calyx 5–6 × 10–15 mm, cupuliform, brown, margin not appressed to fruit, glabrous adaxially, densely stellatepubescent abaxially; margin irregularly 6- or 8-crenately lobed, lobes ca. 3 × 6 mm broad. Fruit 1.6–1.8 × 1.0– 1.2 cm, ovoid, apex shortly pointed, apparently indehiscent; pericarp dry, 0.3–0.5 mm thick, outside golden yellow-stellatetomentose, inside densely pale yellow-appressed-pubescent. Seeds dull dark brown, 1.5–1.6 × 1.0– 1.1 cm, ovoid, smooth, glabrous.

Distribution and habitat: — Styrax chrysocarpus is endemic to Yunnan Province (Guangnan, Malipo and Pingbian counties), China ( Fig. 6 ). It grows by the road or in ravine forests at elevations of 1400–1700 m.

Phenology: —Flowering from April to May; fruiting from August to September.

Conservation status: —From our observations, the Malipo population comprises no more than 30 plants within a radius of 3 km. For the type locality of Styrax chrysocarpus is not determined as a nature reserve, it is at risk of being cut for firewoods because it close to villages which are only about 15 km away from the forest, thus we recommend it be categorized as EN (endangered) under criteria B2b following IUCN Red List categories ( IUCN Standards and Petitions Subcommittee 2019).

Additional specimens examined: CHINA, YUNNAN: Kwang-nan [Guangnan County], specific locality not indicated, 1550 m, 14 March 1940, C. W . Wang 87834 ( KUN); Malipo County, Tiechang Xiang, 1472 m, 3 May 2013, C. L . Xiang et al. 577 ( KUN); Same locality as prior one. E . D. Liu et al. LiuED6087 ( KUN); Same locality as prior one. 1400–1700 m, 22 July 2020, R . Zhang et al. zrr2 ( JXAU); Pingbian County, specific locality not indicated, 1400 m, 9 July 1934, H. T . Tsai 62522 ( A, KUN, LBG, PE, paratypes); Pingbian County, specific locality not indicated, 1500 m, 11 July 1934, H. T . Tsai 62766 ( A, IBSC, KUN, PE, paratypes) .

Notes: — Hwang (1987) presumed to place Styrax chrysocarpus in S. ser. Imbricatae Perkins (1907: 18) because of its similarity of other characters to those species within the series. Huang et al. (2003) further treated S. chrysocarpus in S. series Cyrta , a series with imbricate or subvalvate corolla lobes in bud according to the infrageneric treatment of Styrax by Fritsch (1999). Our study of the flower material of the species shown that the corolla of S. chrysocarpus is imbricate in bud, confirming the infrageneric placement of the species by Hwang (1987) and Huang et al. (2003). S. chrysocarpus is currently known only from southeastern Yunnan. The species identification of a collection with neither flowers nor fruits, and with a disjunct distribution from Yongshan County, Yunnan, i.e. H.T. Tsai 51156 (KUN), which Huang et al. (2003) tentatively cited as S. chrysocarpus , is in doubt because its leaves adaxially and petiole are covered with sparse gray-white pubescence (vs. dense yellow-gray-stellate pubescence in S. chrysocarpus ) and its tertiary veins abaxially are not prominent (vs. prominent in S. chrysocarpus ). This collection needs further field investigation to better understand its identity.

Figures

FIGURE 1. Holotype sheets of Styrax buchananii (E. M. Buchanan 51, E00105737) (A) and S. chrysocarpus (H. T. Tsai 62505, A00018412) (B).

FIGURE 2. Specimens of Styrax buchananii (A, C) and S. chrysocarpus (B, D). A. China, Yunnan, Yingjiang County, W.Y. Zhao & F. Ye zwy-1608 (SYS). B. China, Yunnan, Malipo County, E.D. Liu et al. LiuED6087 (KUN). C. China, Yunnan, Yingjiang County, R. Zhang et al. zrr14 (JXAU). D. China, Yunnan, Malipo County, R. Zhang et al. zrr2 (JXAU).

FIGURE 5. Styrax chrysocarpus from Malipo County, Yunnan, China. A. Habit. B. Flowering branchlet. C. Fruiting branchlet. A and C from R. Zhang et al. zrr2 (JXAU), B from E.D. Liu et al. LiuED6087 (KUN). Photographs A and C by R. Zhang, and B by X.X. Zhu.

FIGURE 6. Styrax chrysocarpus from Malipo County, Yunnan, China. A. Leaf blades in adaxial (left) and abaxial (right) view. B. Flower (apical view). C. Flower (lateral view). D. Calyx (lateral view). E. Stamen (lateral view). F. Ovary and style. G. Fruit (lateral view). H. Seed (lateral view). Note: a, d, g show the indumentum on the abaxial surface of the leaf blade, calyx and pericarp, respectively. All photographs by R. Zhang except B, C, E and F by X.X. Zhu.