Justicia hansenii K. Rueangsawang & Chantar., 2013

Rueangsawang, Kanokorn, Chantaranothai, Pranom & Simpson, David A., 2013, Taxonomic notes on the genus Justicia (Acanthaceae) from Thailand, Phytotaxa 130 (1), pp. 43-49 : 43-45

Justicia hansenii K. Rueangsawang & Chantar. , sp. nov. ( Figs. 1–3 )

J. hansenii resembles J. distincta Imlay (1939: 147) and J. vasculosa ( Nees von Esenbeck 1832: 104) Anderson (1867: 515) but differs in having inflorescences with more numerous spreading lateral branches and finely pubescent calyx, corolla and capsule ( Table 1).

Type: — THAILAND. Prachuap Khiri Khan: Pala-U waterfall, elevation ca. 125 m, 10 March 2010, K . Rueangsawang 258 (holotype KKU!, isotypes BK!, BKF!) .

Perennial herbs; stems erect, 30–60 cm high, terete, slender, glabrous, swollen at nodes. Leaves chartaceous, lanceolate, 8–13 × 2.2–4.5 cm; apex acuminate; base cuneate or slightly oblique; margin entire; cystoliths linear, conspicuous on both surfaces; upper surface sparsely pubescent; lower surface glabrous; lateral veins 5–7 pairs; petioles 2–4 cm long, grooved, glabrous. Inflorescences both terminal and in the upper axils, spikes, 2–11 cm long; rachis glabrous; peduncles 0.5–1.5 cm long, sparsely pubescent; flowers sessile, opposite at inflorescence node, a single flower subtended by one bract and two bracteoles; bract ovate, 1.5– 3.5 × 0.5–1 mm, pubescent, margin ciliate, shorter than calyx; bracteoles ovate to lanceolate, 3–4 × 0.8–1 mm, finely pubescent, margin ciliate, shorter than or as long as calyx. Calyx deeply 5-lobed, greenish, 3–4.5 × 0.8– 1 mm; lobes lanceolate; apex acute, finely pubescent outside, glabrous inside, margin ciliate. Corolla white with purple markings on palate of lower lip, 10–14 mm long, finely pubescent outside; tube cylindrical, 7–8.5 mm long, slightly enlarged in throat; upper lip erect, slightly hooded, emarginate, 4–6 mm long; lower lip spreading, obovate, 6–7.5 × 5.5–6.5 mm, lateral lobes 0.7–1 × 1.5–3 mm, middle lobe 1–1.5 × 1.4–2 mm, narrower than lateral pairs. Stamens 3–5 mm long, sparsely pubescent, inserted near middle of corolla tube; filaments straight; anthers separated, 2-thecous, ca. 1.3 mm long, thecae superposed, subequal; lower theca 0.8–0.9 mm long, with tail 0.1–0.2 mm long; upper theca 0.8–0.9 mm long. Pollen 2-colporate, P = 28.0–48.0 µm, E = 19.4–31.7 µm, prolate ( P / E = 1.44 µm), aperture area with 2 rows of 10–12 insulae. Ovary ovoid or ellipsoid, ca. 1 mm long; style filiform, lower part pubescent, 9–12 mm long; stigma with two minute unequal lobes. Capsules obovoid, apex acute, finely pubescent.

Distribution and ecology: —Only known from the type locality but may be expected in Myanmar. Growing on rocks, exposed areas along streams in evergreen forest, elevation ca. 125 m.

Phenology: —Flowering and fruiting December–March.

Etymology: —The specific epithet “ hansenii ” honours the late Prof. Dr. Bertel Hansen, a taxonomist at the Botanical Museum, University of Copenhagen, Denmark, and an expert in the study of Asian Acanthaceae .

Additional collection studied (paratype): — THAILAND. Prachuap Khiri Khan: Pala-U waterfall, ca. 125 m, 27 December 2008, K . Rueangsawang 185 ( KKU!) .

Note: — Justicia hansenii is closely related to J. distincta . They share a spicate inflorescence, with each bract supporting a single flower, the bract shorter than the calyx and the corolla being white with purple markings on the palate of the lower lip. Justicia hansenii can be distinguished by the 1) numerous, spreading lateral inflorescence branches, 2) finely pubescent calyx, corolla and capsule and 3) middle corolla lobe that is narrower in comparison to the lateral pairs. Justicia hansenii also resembles J. vasculosa , but differs by having lanceolate leaf shape, glabrous inflorescence ( Table 1). At present J. hansenii is known only from the type locality, which is close to the Myanmar border ( Fig. 2 ). It is likely that more populations of J. hansenii will be discovered following further exploration in Thailand and Myanmar.

Figures

FIGURE 1. Justicia hansenii: A. habit of flowering plant; B. bract; C. bracteole; D. opened calyx; E. flower, lateral view; F. flower with opened corolla showing stamens; G. stamen with theca; H. ovary and style (A–H from K. Rueangsawang 258). Drawn by W. Thammarong.

FIGURE 2. Distribution of J. hansenii in south-eastern Thailand. Closed circle (·) indicates collection locality.

FIGURE 3. Justicia hansenii: A. habit; B. inflorescences; C. flowers; D. fruit; E. pollen, SEM image, equatorial view (from K. Rueangsawang 258, scale bar = 30 µm).