Derris solorioides Sirich. & Adema, 2014

Derris solorioides Sirich. & Adema View in CoL , sp. nov. — Fig. 2 View Fig , 3 View Fig

Morphologically highly similar to Derris marginata but growing on rugged limestone terrain. Inflorescences basal lateral branches sometimes subtended by leaf-like bracts. Flowers white with pale greenish hue, obviously smaller than D. marginata . Ovary with more (c. 8) ovules than D. marginata (4–5). Pods with only a single wing along the upper suture, pericarp around seeds darker in dry pods, but without thickening. — Type: Sirichamorn YSM 2013–1 (holo L; iso BK, BKF,L), Thailand, Nakhon Sawan,Tham Phet Tham Thong Forest Park, Doi Chawn Duea, Takli Subdistrict, in flowers & young fruits, 8 Jan. 2013.

Lianas. Twigs up to 10 mm diam, glabrous, lenticellate. Stipules caducous, triangular, 1–1.5 by c. 1.5 mm, outside glabrous or thinly sericeous, inside glabrous. Leaves with 5–9 leaflets; young leaves light green; petiole 3–9.5 cm long, striate, glabrous; rachis 4.5–11 cm long, striate, glabrous; pulvinus 5–10 mm long, glabrous. Stipellae absent. Leaflets chartaceous to subcoriaceous, broader leaflets usually found in plants growing in shadier areas; terminal one (narrowly) elliptic or (narrowly) obovate, 6–12.5 by 2.7–5.5 cm, length/width ratio 1.6–2.2, base cuneate, obtuse to rounded, apex obtuse or slightly emarginate, upper and lower surface glabrous, midrib slightly raised in a furrow above, distinctly raised below, veins raised on both sides, 7–15 per side, 5–20 mm apart, not reaching the margin but curving upwards, sometimes anastomosing near the margin, venation reticulate; lateral leaflets (narrowly) elliptic to (narrowly) ovate or (narrowly) obovate, 4.5–11 by 2.2–5.5 cm, length/width ratio 1.8–2.2; pulvinus of petiolules 4–6 mm long. Inflorescences axillary panicles or sometimes terminal, 11– 21 cm long, peduncle 5– 20 mm long, glabrous or thinly strigose, striate; lateral branches 1–10 cm long. Bracts subtending lateral branches ovate-triangular, 0.8–1.2 by 0.8–1.3 mm, outside glabrous to thinly sericeous, inside glabrous but with some hairs at base, margin ciliate, sometimes leaf-like. Brachyblasts absent. Bracts subtending flowers elliptic to ovate, 0.8–1 by 0.3–0.4 mm, both sides glabrous or with few hairs, margin ciliate. Pedicels slender, 7–10 mm long, glabrous. Bracteoles at the upper part of pedicels, narrowly elliptic to ovate, 0.6–0.7 by 0.2–0.3 mm, both sides glabrous, margin ciliate. Calyx greenish, cup-shaped, 2.5–3 mm high, outside glabrous, with hairs near the lobes, inside glabrous, margin ciliate, tube 2–2.5 mm high, upper lip indistinct or with two short lobes, 0.2–0.3 by 0.7–1 mm; lateral lobes triangular or semi-circular, 0.5–0.7 by 1.2–1.7 mm; lower lobe triangular or semi-circular, c. 0.7 by 1.5–1.6 mm. Corolla white or slightly with pale green hue. Standard: claw 3.3–3.5 mm long; blade broadly obovate to orbicular, 5.5–7 by 5–5.7 mm, basal callosities absent, apex emarginate, both sides glabrous. Wings: claw 3–3.5 mm long; blade elliptic, 6–7 by 1.7–2.3 mm, apex rounded, both sides glabrous, upper auricle c. 1 mm long, lower auricle indistinct, lateral pocket 0.7–1 mm long, sometimes indistinct. Keel petals: claw 2–2.5 mm long; blade boat-shaped, 5.5–6 by 2–2.5 mm, apex rounded, outside glabrous except for the apical part with few hairs, inside glabrous, upper auricle indistinct, lateral pocket 1–2 mm long. Stamens monadelphous, with basal fenestrae, 8–9.5 mm long, free part 2.5–3 mm long, glabrous; anthers 0.4–0.5 by 0.3–0.45 mm, glabrous. Disc annular or indistinct. Ovary 4–5 mm long, stipe indistinct, slightly hairy; ovules c. 8; style 4–4.5 mm long, slightly hairy. Pods elliptic to strap-like, 4.5–8 by 1.8–2.2 cm, glabrous, with a wing along the upper suture, 2 – 4 mm wide, seed chamber absent but darker area around seed present in pericarp of dry pods, without thickening of the pericarp. Seeds 1–2 per fruit or sometimes immature, discoid, flat, 13–14 by 10–11 by 1–2 mm; hilum central, 1–1.4 mm long.

Distribution — This species is endemic to North-Central Thailand.

Habitat & Ecology — This species is found in deciduous forest, seasonally damaged by fire, on rugged limestone terrain in a partly open place at 100–375 m altitude. Flowering: De- cember to February; fruiting January to April.

Vernacular names — Hang Lai Khao, Hang Lai Khao-Khao Poon.

Additional material. THAILAND, Nakhon Sawan, Tham Phet Tham Thong Forest Park, Doi Chawn Duea , Takli Subdistrict , Maxwell 05-75 ( L), mature infructescence, 25 Jan. 2005 .