Helicteres ubonensis (Malvaceae), a new species from Thailand Author Kantachot, C. Author Chantaranothai, P. text Blumea 2024 2024-01-17 69 13 15 https://doi.org/10.3767/blumea.2024.69.01.02 journal article 10.3767/blumea.2024.69.01.02 2212-1676 16856085 Helicteres ubonensis Chantar. & Kantachot , sp. nov. — Fig. 1–2 Etymology . The specific epithet refers to the collections from Ubon Rat- chathani province where the species was discovered. Typical of this species are narrowly elliptic-oblong leaves. Corolla purplish white or pinkish. Capsule pointed as beak at the apex and surface covering with stellate hairs. — Type : P . Chantaranothai , C . Kantachot & P . Kludwong 2021-150 (holo KKU ; iso AAU , QBG ), Thailand , Khong Chiam , Napho Klang , along trail to Soi Sawan Waterfall , 10 Aug. 2019 . Shrub, 1–2 m tall; twigs erect and some ascending, terete, young twigs brownish, glabrescent; twigs blackish, glabrescent; bark thick with fibres. Leaves spiral, narrowly elliptic-oblong, (8–) 10–15 by (1–) 2–3 cm , chartaceous, apex acute or acuminate, base cuneate or obtuse, margin entire, upper surface green, glabrous or glabrescent, lower surface pale green, with stellate hairs; midrib prominent on the lower surface; basal veins 3; lateral veins (3–)5–8 pairs; petioles 4–9 mm long, terete, hairy; stipules caducous. Inflorescences axillary or terminal, cymes, epicalyx present; peduncle 4–5 mm long, hairy. Flowers valvate, with short pedicels. Calyx campanulate, with 5 lobes, lobes unequal, green, hairy. Petals 5, free, spathulate, 7–9 by 4–5 mm , purplish white or pinkish. Androgynophore c. 5 mm long. Stamens 10, alternating with 5 staminodes, filament column glabrous; anther c. 0.5 mm long. Stigma 5, pointed apically. Ovary superior, surrounded by the filament column, longitu- dinally 5-lobed, hairy; style c. 1 mm long; ovules numerous, 8 per locule. Fruit capsular, cylindric, straight, pointed at the apex,2.5–3.5 by 0.7–1 cm , fruit stalk 2–6 mm long; young fruit green, mature fruit brown, with stellate hairs. Seeds rhomboid, 2–3 by 1.5–2 mm , dull black. Distribution — Thailand ( Ubon Ratchathani : Khong Chiam, Soi Sawan Waterfall and Pha Taem National Park). Habitat & Ecology — In open space on rock platform with dry evergreen forest. Flowering and fruiting at least in July–October. Vernacular name — Khi on ging dum (ขี้อ้นกิ่งดำ�). Fig. 1 Helicteres ubonensis Chantar. & Kantachot. a. Habitat; b. twigs and leaves; c, d. capsule. — Photos: Chortip Kantachot. Fig. 2 Helicteres ubonensis Chantar. & Kantachot. a. Leaves and capsules; b. lower surface of leaf with stellate hairs (black dots); c. flower; d. seeds (a, b, d: P. Chantaranothai et al. 2021-150 , c: C. Kantachot 2020-32 , all KKU). — Drawing by Puntiwa Krachai, 2023. Additional collections studied ( paratypes ) . S . Poompo 10 (deposited at Department of Biological Science Herbarium , Ubon Ratchathani University ), Thailand , Ubon Ratchathani , Khong Chiam , Huai Phai , Pha Taem National Park , s.d .; C. Kantachot 2020-32 (KKU), Thailand , Ubon Ratchathani , Khong Chiam , Napho Klang , Soi Sawan Waterfall , along Sae Soi creek , 30 July 2020 . Notes — Helicteres ubonensis is similar to H. angustifolia L. but differs in having narrow leaves, which are more or less oblong or elliptic-oblong, twigs brownish or blackish. It is also distinctive in the apically narrowed to pointed stigma, absence of setose hairs on the capsule surface and the capsule apex beaked ( Table 1 ). Table 1 Morphological comparison between H. angustifolia and H. ubonensis , morphological characteristics are adopted from Phengklai (2001) .

Characters / Species	H. angustifolia	H. ubonensis
Leaf – shape – petiole length	elliptic, oblong or lanceolate 3–5 mm	narrowly elliptic-oblong 4–9 mm
Flower – colour – petal size (length by width)	bluish or pink 5–10 by 1–2 mm	purplish white or pinkish 7– 9 by 4–5 mm
– stigma shape	flattened	pointed apically
Capsule – surface covered – presence of beak at the apex	setose hairs absent	stellate hairs present

NEW KEY TO THE SPECIES OF HELICTERES FROM THAILAND Because of the discovery of several new species and new records, a new identification key to the species of the genus Helicteres for Thailand is provided: 1. Leaf margin entire or rarely with a few minute teeth near apex....................................... 2 1. Leaf margin serrate or dentate from base........... 9 2. Stems prostrate............................... 3 2. Stems erect or ascending....................... 4 3. Upper surface of leaves hairy; basal veins 3............................................ H. oblongifolia 3. Upper surface of leaves glabrous; basal veins 5........................................... H. prostrata 4. Inflorescence a lax thyrse............. H. thailandica 4. Inflorescence a short cyme...................... 5 5. Leaf margin entire. Stigma flattened, slightly 5-lobed..................................... H. angustifolia 5. Leaf margin entire or slightly serrate near apex. Stigma simple, narrowed to a point or divided into 5 teeth.... 6 6. Young twigs glabrous or sparsely hairy............. 7 6. Young twigs hairy.............................. 8 7. Leaves lanceolate or oblong-lanceolate. Capsule with vil- lous hairs.......................... H. lanceolata 7. Leaves narrowly elliptic-oblong. Capsule without villous hairs.............................. H. ubonensis 8. Leaves coriaceous, scabrous on upper surface. Apex of capsule without beak..................... H. lanata 8. Leaves chartaceous, glabrous on upper surface. Apex of capsule with beak..................... H. geoffrayi 9. Leaves ovate, broadly ovate to more or less rounded 10 9. Leaves oblong-lanceolate or oblong-ovate......... 11 10. Capsule twisted. Lower surface of leaves glabrescent or scabrous............................... H. isora 10. Capsule not twisted. Both surfaces of leaves with soft hairs.................................. H. viscid 11. Leaves chartaceous. Calyx less than 1 cm long. Capsule 1.5–2 cm long........................ H. elongata 11. Leaves coriaceous. Calyx more than 1 cm long. Capsule 2.5–5 cm long......................... H. hirsuta