Styrax buchananii W.W. Smith (1920: 304)

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 : 174-178

Styrax buchananii W.W. Smith (1920: 304) . Figs. 1A , 2A, C , 3–4 .

TYPE:— Myanmar. Kachin State, Myitkyinâ District, in Mara Nantan forest, Kaukkwe Valley , 606 m, March 1912 , E. M. Buchanan 51 (holotype, E00105737 !; isotype, E00105737 !) .

Styrax serrulatus var. latifolius Perkins (1907: 37) . Type:— Myanmar. Mandalay Division , W. Griffith 3670 (lectotype designated by Huang et al. (2003: 503), K K000728982 !; isolectotypes: GH00306313 , K000728983 , P00559001 ) .

Trees 5–12 m tall. Young branchlets densely yellow-brown-stellate-pubescent; older branchlets becoming gray, subglabrous. Petiole 3–7 mm long, densely yellow-gray-stellate-pubescent. Lamina of fertile shoots 6–11 × 4–6 cm, those of sterile shoots up to 16 × 11 cm, chartaceous, ovate-oblong, base rounded or broadly cuneate, apex slightly acuminate to obtuse, rarely truncate; adaxially with sparse yellow-gray stellate trichomes or pubescent and abaxially with dense yellow-gray stellate trichomes, prevalent on veins; margin remotely irregularly serrulate apically; secondary veins 4 to 7 on each side of midvein, adaxially faintly prominent, abaxially prominent; tertiary veins parallel and perpendicular to secondaries, slightly sunken adaxially, abaxially prominent. Fertile shoots 10–25 cm long, 3- to 5- leaved. Inflorescences arising from shoots of current growing season; lateral inflorescences racemose, 2–5 cm long, 3- to 5-flowered, often with 1 or 2(to 4) flowers occurring in same leaf axil; pseudoterminal inflorescences usually paniculate, sometimes racemose, 5–13 cm long, 5- to 22-flowered, lateral branches 0 to 5, sometimes with 2 or 3 short lateral racemes from base of inflorescence, rachis and branches densely yellow-stellate-pubescent. Pedicel (3–)4–6(– 10) mm long, densely gray-stellate-hirsute; bracteoles ca. 3 mm long, linear, usually positioned at base of pedicels. Flowers 1.3–1.6 cm long. Calyx 4.0–5.5 × 4–5 mm, cupuliform; adaxially white appressed-pubescent with 2- or 3- armed or stellate trichomes; abaxially densely off-white-stellate-hirsute, brown when dry; margin truncate, undulate, or irregularly lobed, teeth minute and not contiguous if present. Corolla 0.9–1.1 cm long, white, tube ca. 3 mm long, glabrous, lobes 5, 8–11 × 3.0– 4.5 mm, lanceolate or ovate-lanceolate, stellate-tomentose on both sides. Stamens 10; filaments ca. 5 mm long, distally flexuous and attenuate, densely white- to yellow-stellate-hirsute throughout, arms of trichomes predominantly pointing upward; anthers 5–6 mm long, wider than distal portion of filament; connectives (at least proximally) densely stellate-hirsute. Style densely white-stellate-hirsute nearly throughout, thinning distally; stigma 0.4–0.7 mm wide, punctiform. Infructescences arising from shoots of current growing season, racemose, 3- to 18-fruited, densely gray-stellate-tomentose. Fruiting pedicel 6–8 mm long. Fruiting calyx 8–9 × 10–13 mm, cupuliform, whitish brown, margin appressed to fruit, glabrous adaxially, densely stellate-pubescent abaxially; margin irregularly 5- or 6-crenately lobed, lobes ca. 3 × 5 mm broad. Fruit 1.3–1.5 × 1.0– 1.1 cm, ovoid, apex minutely pointed, indehiscent; pericarp dry, ca. 1 mm thick, outside white-stellate-tomentose, inside densely white-appressed-pubescent. Seeds dull black, 1.1–1.3 × 0.8–0.9 cm, ovoid, smooth, glabrous.

Distribution and habitat: — Styrax buchananii is distributed in Kachin State, Mandalay Division, and Sagaing Division, Myanmar, and is also found in Longchuan, Tengchong and Yingjiang counties, Yunnan Province, China ( Fig. 7 ). It grows in valley forests at elevations of 600–1800 m.

Phenology: —Flowering from March to April; fruiting from July to September.

Conservation status: —The population by the road from Husa to Longba in Longchuan County, which is not determined as a nature reserve, is the first site in China in which Styrax buchananii was recorded (Zhao et al. 2020). This population comprises no more than 20 plants within a radius of 2 km, and is adjacent to the villages and not yet recognized by the local people. It may be at risk of cutting for firewood or other uses. As the conservation status of the population in Myanmar is not clear, we do not recommend an evaluation of the IUCN status of the species.

Additional specimens examined: — CHINA. Yunnan: Longchuan County, by the road from Husa to Longba , 1778 m, 3 April 2020, W. Y . Zhao & F . Ye zwy-1593 ( SYS); Tengyueh [Tengchong County], specific locality not indicated, E. B . Howell 279 ( E); Yingjiang County, by the road from Bangzhong village to Dazhai River , 1690 m, 4 April 2020, W. Y . Zhao & F . Ye zwy-1606 ( JXAU, IBSC, SYS); Same locality as prior one, 1690 m, 22 July 2020, R . Zhang et al. zrr14 ( JXAU); Yingjiang County, mountains behind Jinzhuzhai in Tongbiguan , 24 April 2013, Y. J . Guo et al. 12cs7452 ( KUN) . MYANMAR. Bhamo District: the road to Sinlumkaba , 1200 m, 5 April 1912, J. H . Lace 5737 ( E, paratype); Bhamo District : specific locality not indicated, 1500 m, 10 April 1912, J. H . Lace 5774 ( E, K); Myitkyinâ District: Japing Valley , 1200 m, March 1922, G . Forrest 21083 ( E); Lamaing , E. M . Buchanan 21 ( E, paratype); Sumprabum Subdivision, Hlingnan , Y . Hla & C . Koko 3746 ( K); Sumprabum Subdivision, specific locality not indicated, 915 m, 18 February 1953, F . Kingdon-Ward. 20550 ( A, BM, E); Taunggyi District: Sagaing Division , Patkoi Range , the border between Burma [Myanmar] & India , specific locality not indicated, 22 June 1921, R. S . Hole 17 ( K) .

Notes: — Huang et al. (2003) noted that Styrax odoratissimus Champion (1852: 304) is a close relative of S. buchananii and also stated that S. chrysocarpus is another probable close relative. Styrax odoratissimus can be easily distinguished from S. buchananii by its leaf blade usually glabrous except on the midvein (vs. with sparse or dense yellow-gray stellate trichomes especially on the major veins) and smaller (0.8–1.0 × 0.6–0.8 cm vs. 1.3–1.5 × 1.0– 1.1 cm) fruit usually with a prominent rostrum (vs. minutely apiculate) apex. However, differences between S. buchananii and S. chrysocarpus have not been as clear because of similarity in vegetation organs, and the absence of data from flowers in S. chrysocarpus and fruits in S. buchananii ( Huang et al. 2003) . In this regard, we observed that one specimen of S. buchananii collected from Yingjiang, i.e. Y.J. Guo et al. 12cs7452 (KUN), was incorrectly identified as S. chrysocarpus . With the flowering and fruiting material generated from this study, we find that S. buchananii can be distinguished from S. chrysocarpus by its flexuous filaments (vs. straight), fruit calyx up to 1/2 the length of fruit (vs. 1/3), smaller fruit with thicker pericarp, and smaller dull black (vs. dull dark brown) seed, among other characters ( Table 1).

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 3. Styrax buchananii from Yingjiang County, Yunnan, China.A. Habit, the arrow shows S. buchananii. B. Flowering branchlet. C. Fruiting branchlets. A and C from R. Zhang et al. zrr14 (JXAU), B from W.Y. Zhao & F. Ye zwy-1606 (JXAU). Photographs A and C by R. Zhang, and B by W.Y. Zhao.

FIGURE 4. Styrax buchananii from Yingjiang County, Yunnan, China. A. Leaf blades in adaxial (left) and abaxial (right) view. B. Flower (lateral view). C. Flower (lateral view). D. Calyx (lateral view). E. Stamen (lateral view). F. Fruit (lateral view). G. Fruit cut longitudinally to show thick pericarp. H. Seed (lateral view). a, d, f show indumentum on the abaxial surface of leaf blade, calyx and pericarp, respectively. All photographs by R. Zhang except B, C and E by W. Y. Zhao.

FIGURE 7. Geographic distribution of Styrax buchananii (●) and S. chrysocarpus (★).