Polyosma pilosa Esser, 2015

Esser, Hans-Joachim & Saw, Leng Guan, 2015, A new species of Polyosma (Escalloniaceae / Polyosmaceae) from Thailand and new synonyms, Phytotaxa 221 (1), pp. 89-92 : 90

Polyosma pilosa Esser , sp. nov. ( Fig.1 )

A species easily separated from all other Thai species by the characteristic pilose indumentum of remarkably long [1–2(–3) mm] hairs on all parts, in particular on both leaf sides (0.1–0.5 mm long in the other Thai taxa).

Type:— THAILAND. Chaiyaphum: Phu Khieo Wildlife Sanctuary , 700 m, 03 May 1997 (fl), R . Pooma 1540 (holo BKF SN 099365!, iso BKF SN 099364!) .

Tree to 15 m tall. Indumentum consisting of 1–2(–3) mm long, loosely erect, simple hairs of yellowish(-brown) colour, appearing nearly golden. Leaves: petiole 10–15 mm long, densely pubescent; blade chartaceous, 12–19 by 4–6 cm, obovate(-elliptic), base acute, margin entire in lower half, distinctly dentate in upper half with the teeth 8–10 mm apart, apex acuminate, only slightly brighter below, above and below with scattered hairs on the whole surface and with dense hairs on margin, midvein and sideveins, side veins distinct on both sides, in 11–15 pairs, veinlets only visible below. Inflorescences terminal, racemose, creamy, 9–14 cm long, with c. 35–85 flowers, distinctly to densely pubescent on all surfaces, even more so on pedicels and calices; bracts 3–5 mm long, bracteoles 2–3 mm long, at base of pedicel or along the upper part of it. Flowers: pedicel 1 mm long; calyx tube 1–2 mm long, sepals 4, the free lobes c. 1 mm long; corolla 8–10 mm long; petals 4; inner parts not seen. Fruits green; pedicel to 5 mm long, pubescent; drupe 1-seeded, 10–11 by 5–5.5 mm, ovoid, obtuse at both ends, smooth and not ribbed, with scattered hairs.

Additional specimens studied (paratypes): — THAILAND. Chaiyaphum: Phu Khieo Wildlife Sanctuary , 1000 m, 12 July 1973 (fr), T . Smitinand 11873 (BKF-3 sheets!), same place, 1000 m, 22 February 1931 (fl), A . F . G. Kerr 20214 ( B!, BK!, BM!, K!, L) .

Distribution: —Endemic.

Ecology: —Along roads in shaded mixed evergreen forest; elevation 700–1000 m. Flowering in February, May, fruiting in July.

Thai name: —Me hang.

Notes: —This species was not included by Craib (1931). It is similar to the Indochinese Polyosma dolichocarpa Merrill (1938: 32) , described from Vietnam. Both taxa are the only ones in SE Asia with a long-pilose indumentum. Polyosma dolichocarpa differs however sufficiently in distinctly sulcate fruits and longer (2–3 mm) pedicels in flowers.

Schulze-Menz annotated specimens of this new species as Polyosma dolichotricha , a name that remained unpublished like so many other names he suggested. But to prevent possible confusion with P. dolichocarpa , we here propose a different name.

Polyosma wallichii Bennett (1840: 196) . Lectotype (designated here):— BANGLADESH. Chittagong Division: Silhet, in montibus Pandooah, s. dat. (fl), N. Wallich 8471 (BM!, isolectotypes G!, K!, K-W).

Polyosma elongata Geddes (in Craib 1928: 66), syn. nov. Type:— THAILAND. Chiang Mai: Doi Angka [= Doi Inthanon], 01 May 1921 (fl), A. F .G. Kerr 5289 (holo K!, iso B!, BK!, BM!, E!, P, TCD!) .

Note: —The thin leaves and the smooth fruits with oblique base are typical for P. wallichii . The Thai plants (with soon glabrescent leaves with appressed hairs) differ slightly from collections from India, Bangladesh and Myanmar (slowly glabrescent leaves with mostly erect hairs), whereas flowers and fruits are indistinguishable. Therefore the two are proposed here as synonyms.

Figures

FIGURE 1. Polyosma pilosa Esser. a. Habit; b. detail of leaf showing long hairs; c. flower bud; d. flower bud with part of corolla removed; e. style and stigma; f. stamen; g. fruit [a–f: Pooma 1540; g: Smitinand 11873; all BKF]. Drawing: Esmée Winkel 2013.