Curcuma spathulata Škorničk. & Soonthornk., 2021

3. Curcuma spathulata Škorničk. & Soonthornk. View in CoL , sp. nov. (subg. Hitcheniopsis) — Fig. 3 View Fig

Similar to Curcuma parviflora Wall. in its small habit, inflorescence with distinct white coma bracts and flowers with distally purple labellum, but differing by coma bracts pure white without green tips, fertile bract supporting 4–6 flowers, flowers with prominently spathulate deeply bilobed labellum blotched red at base and almost linear staminodes, with red streaks at base (vs coma bracts with green tips, fertile bract supporting 2 or 3 flowers, flowers with obovate labellum white at base, pure white and bluntly triangulate staminodes in C. parviflora ). — Type: Sutthinut Soonthornkalump Sutt-212 (holo BKF, including flowers in spirit as part of a single specimen; iso SING, including flowers preserved in spirit as part of a single specimen), Thailand, Tak Province, Sam Ngao District, Sam Ngao Subdistrict , Bhumibol Dam , 400 m elevation, 24 July 2020 .

Etymology. The specific epithet is derived from Latin spathulatus = spathulate, and refers to the shape of the labellum.

Perennial rhizomatous herb, 30–40 cm tall. Rhizome ovoid, 1.5–3.4 by 0.9–1.5 cm, occasionally with a lateral branch 1.8–2 by c. 0.5 cm, externally yellowish white (young rhizome) to pale brown, covered with rusty coloured and decayed scales, internally yellow, aromatic and with slightly sweet taste; root tubers ovate to fusiform, 1–1.5 by 0.4–0.8 cm, externally light brown, internally white. Leafy shoot with 5 or 6 leaves at anthesis; pseudostem 10 –26 cm long, composed of 1 or 2 leafless sheaths and 5 or 6 leaf sheaths, all plain green, glabrous; ligule up to 1 mm long, obscurely bilobed, hyaline, greenish white, semi-translucent, glabrous; petiole 6.5–14 cm long, canaliculate, green, glabrous; lamina elliptic-ovate to elliptic, 9.5–14.6 by 3.8–4.5 cm, adaxially dark green, abaxially somewhat paler, glabrous on both sides, midrib green, margin hyaline, c. 0.1 mm wide, glabrous, base obtuse to slightly oblique, apex acuminate to narrowly acuminate. Inflorescence central; peduncle exceeding pseudostem by 2–4.5 cm, light green (on exposed part), glabrous; thyrse 5–7.2 by 2–2.5 cm, composed of 12–18 fertile bracts and 3 or 4 coma bracts; coma bracts ovate, 1.8–1.9 by 0.8–0.9 cm, apex acute, white, glabrous on both sides; bracts broadly ovate to obovate, 19–20 by 15–18 mm, connate in basal 1/2, pale green to cream with white, glabrous on both sides, apex broadly acute to almost obtuse, strongly reflexed; cincinni with up to 6 flowers at the most basal bracts, the number gradually decreasing upwards; bracteoles triangular to elliptic, 5–7 by 3–3.5 mm wide at base (outer ones largest), hyaline, semi-translucent white, glabrous, apex obtuse, slightly concave. Flowers 2–2.3 cm long, exserted from bracts; calyx 3.5–4 mm long, tridentate, with unilateral incision 0.5–0.7 mm deep, teeth c. 0.5 mm long with blunt apex, semi-translucent white, glabrous; floral tube 9.5–10 mm long, narrowly cylindrical at base, slightly widening distally, externally white, glabrous, internally white and glabrous, distally (near throat) white, puberulous in apical half; dorsal corolla lobe broadly ovate, 3.9–4.5 by 3.3–3.5 mm, white, glabrous, apex hooded; lateral corolla lobes ovate to bluntly triangular, 4–4.3 by c. 3.9 mm wide at base, apex obtuse reflexed, white, glabrous; labellum spathulate, 10–10.5 by 7–8 mm (gradually narrowing to 2 mm at base), bifid with an incision c. 4 mm long, white with bright red patches and spots in basal half, distally purple, lobe margins irregularly undulate, glabrous; lateral staminodes oblong, 2.3–3 by 0.6–0.7 mm, white with two red streaks in basal 1/3–1/4, glabrous on both sides; stamen c. 3.5 mm long; filament c. 1.5 mm long, c. 1.2 mm broad at base, c. 0.5 mm at point of attachment, white, glabrous; anther spurless, ovate, 2–2.1 mm long (including crest), 1–1.2 mm wide at base, connective tissue white, with glandular hairs on sides and abaxially; anther crest obtuse (sometimes slightly emarginate), c. 0.4 by 1.5 mm wide at base, white; anther thecae c. 1.5 mm long, dehiscing along entire length, white, pollen white; epigynous glands absent; style white, glabrous; stigma unequally funnel-shaped (dorsal side longer), c. 0.9 by 0.7 mm, white; ostiole with smooth to finely irregularly denticulate margin (no hairs), facing forward; ovary ovoid, 1.3–1.5 by 1.0– 1.4 mm, trilocular, white to cream white, glabrous, placentation axile. Fruit and seeds not seen.

Distribution — Known only from Tak Province in northern Thailand.

Habitat & Ecology — Mixed deciduous forest and hill ever- green forest at 400–700 m elevation. Flowering starts in the rainy season and lasts from June to September, although in cultivation the species may start flowering in May. The plants enter dormancy in November. The flower opens in the morning and wilts in the afternoon or even earlier if exposed to strong sunlight and high temperature.

Conservation status — The number and extent of populations of this species, which we obtained from a local market, are unknown, and the species has to be treated as Data Deficient.

Vernacular names and Uses — Dok khao tok noi ( ดอกข้าว ตอกน้อย) = little popped rice flower. There are no uses recorded but the plants are sold as ornamentals in local markets.

Notes — Curcuma spathulata is a small plant and in herbarium material most likely to be confused with C. parviflora to which it is compared in the diagnosis. Curcuma thorelii Gagnep. is another species with a white coma, green fertile bracts and purple flower with prominently bi-lobed labellum. However, this species is far more robust with more rigid bracts and therefore not likely to be confused even in herbarium material. Further- more, the flowers of C. thorelii have a labellum with white base and staminodes which are of the same purple colour as the labellum, extending far beyond the corolla lobes and well visible in front and side view (see Leong-Škorničková et al. 2013: f. 2B, reprinted in colour in 2014) as oppose to labellum with white base with reddish spots and narrow almost linear white staminodes which are hardly visible in both views.