Zingiber castaneum Škorničk. & Q.B.Nguy

Leong-Škorničková, Jana, Bình, Nguy ễn Qu ốc, Đăng, Tr ần H ữu, Šída, Otakar, Rybková, Romana & Vương, Trương Bá, 2015, Nine new Zingiber species (Zingiberaceae) from Vietnam, Phytotaxa 219 (3), pp. 201-220 : 209

Zingiber castaneum Škorničk. & Q.B.Nguy ễn, sp. nov. (sect. Dymczewiczia)

Similar to Zingiber mellis in having upright inflorescence and similar flower colour, but differs by the thinner bright green laminae, green papery ligules, reflexed bracts, shape of the labellum and anther with pronounced filament.

Type: — VIETNAM, Ninh Bình Province, Cúc PhƯƠng N. P., Cây S ấu C ổ Thụ trail, 397 m, 20°21’28.16”N, 105°34’52.96” E, 11 September 2011, Nguyễn Quốc Bình & Trần H ữu Đăng VNM-B 1370 (holotype SING (incl. spirit), isotype VNMN). Fig. 4 .

Rhizomatous herbs forming small clumps. Rhizome creeping, to 1.5 cm in diam., externally light brown, internally cream white, aromatic (somewhat unpleasantly), scales broadly triangular, c. 1 cm long, light brown, glabrous. Leafy shoot c. 0.75 m tall, with 6–9 leaves, basal 1/3–1/2 leafless; bladeless sheaths and leaf sheaths mid green, glabrous; ligule 5–7 mm long, ovate, translucent light green, glabrous; petiole absent; lamina sessile, up to 25 × 7.8 cm, elliptic, gradually tapering to caudate apex, base rounded, above glossy green, lighter green beneath, fairly thin in texture, mildly plicate, glabrous both sides. Inflorescence terminal, in upright position; spike 6–9 cm long, 3.0– 3.5 cm broad (inclusive tips of reflexed bracts), consisting of 7–11 bracts; bracts green (turning yellow with age), glossy, obovate, lowermost bract sterile, fertile bracts up to 3 cm long and 2.8 cm broad (largest in the middle of the inflorescence), with broadly acuminate reflexed apex; cincinnus of 3 flowers per bract (2 or 1 flower per bract towards the apex); bracteole triangular-ovate, c. 11 mm long, up to 10 mm broad at base, unequally folded, translucent white with greenish apex, glabrous externally and internally. Flower c. 5 cm long; calyx 9–11 mm long, translucent white, glabrous, with no conspicuous teeth at apex (appears to be truncate), with unilateral incision 4–5 mm; floral tube c. 29 mm, externally and internally white, externally and internally glabrous; dorsal corolla lobe ovate-triangular, 18–22 × 11–13 mm, semi-translucent pale yellow, darker towards apex, externally and internally glabrous, apex acute, mucronate, mucro c. 1 mm; lateral corolla lobes ovate triangular, 18–20 × 9–10 mm, semi-translucent light yellow, darker towards apex, externally and internally glabrous, apex narrowly acute; labellum 17–18 mm long, c. 12.5–14.0 mm broad, ovate to weakly obovate, dark maroon with pale yellow lines radiating from the base to about third of the labellum and small pale yellow blotches near margins, velvety in appearance; lateral staminodes 10–11 × 2–3 mm, oblong, connate to labellum by basal 1 mm, yellow. Stamen 17–18 mm long; filament 2–3 mm long, 3 mm broad at base, 2.5 mm broad at apex, cream white, glabrous; anther 16–18 long (with anther crest straightened), 2.5–3.0 mm broad, connective tissue yellow, glabrous, anther crest 6.5–8.0 mm long, wrapped around stigma, richly tinged with maroon towards the apex, glabrous; anther thecae 8–9 mm long, dehiscing along entire length. Epigynous glands two, c. 4 mm long, c. 0.5 mm in diam., cream white. Ovary nearly cylindrical to weakly obconical, 3.0–4.0 × 2.5 mm, white, glabrous, trilocular with central placentation. Style white, glabrous, stigma c. 1.5 mm long, slightly thicker than style, white, ostiole front facing, ciliate. Fruit and seeds not seen.

Etymology:— The Latin epithet refers to the chestnut colour of the labellum.

Distribution & IUCN preliminary assessment:— So far known only from the type collection in Cúc PhƯƠng National Park, Vietnam. Because the number of populations and their sizes are not well known, we suggest to treat this species as Data Deficient until more information is available.

Ecology and phenology:— Growing in broad-leaved evergreen forest, in transition area to lime stones, at altitude about 400 m. Flowering starts in July and extends to September.

Zingiber castaneum is easily recognized among other terminally flowering species by its upright inflorescence with reflexed bracts.

Figures

FIGURE 4. Zingiber castaneum.A. Habit. B. Inflorescence with flower in side view. C. Detail of ligule. D. Flower (front view). E. Flower (semi-front view). F. Flower from the side view, lateral corolla lobes with dorsal lobe in between, labellum with lateral staminodes and bracteole (scale bar in mm). G. Detail of ovary and epigynous glands and anther (side and front view) (scale bar in mm). Photo: Jana Leong-Škorničková.