Thismia, Griffith, 1845

Nuraliev, Maxim S., Yudina, Sophia V., Truong, Ba Vuong, Do, Thi Xuyen, Luu, Hong Truong, Kuznetsov, Andrey N. & Kuznetsova, Svetlana P., 2020, A revision of the family Thismiaceae (Dioscoreales) in Cambodia, Laos and Vietnam, Phytotaxa 441 (3), pp. 229-250 : 239-240

Thismia . mucronata Nuraliev in Nuraliev et al. (2014: 246 , Fig. 1–3 ) ( Fig. 4 )

Literature:— Kumar et al. (2017: 232), Nuraliev et al. (2019: 150, Fig. 1J )

TYPE:— VIETNAM. Lam Dong Province: Bao Lam District, Loc Bac Municipality, 22.2 km NNW of Bao Loc town, in the forest, not far from river, elevation ca. 1000 m a.s.l., N 11°44’18’’ E 107°43’22’’, 13 April 2013, M. S. Nuraliev 813 (holotype: MW: MW 0591768!, including plants with flowers in liquid collection at Moscow University).

Images of holotype available at https://depo.msu.ru/open/public/item/ MW 0591768/img/0.jpg?original

Description

Plant generally glabrous, branching by the formation of root suckers. Roots vermiform. Leaves 3–11, scattered, up to 7 mm long. Flowers rarely terminal and solitary, usually in terminal monochasial inflorescence of up to 3 flowers.Terminal flowers surrounded by an involucre of (2)3 bracts; lateral flowers surrounded by an involucre of 2 or 3 bracts (floral prophylls). Plane of inflorescence branching transversal; monochasium type a bostryx or a cincinnus. Involucral bracts up to 9 mm long. Pedicel (internode between involucral bracts and ovary) less than 1 mm long. Flower actinomorphic, 12–17 mm long from ovary base. Hypanthium obconic, (4.5) 5–8 mm long (excluding inferior ovary), ca. (5.7) 6–7.5 mm wide in the upper part; involucral bracts reaching about two thirds of hypanthium; outer hypanthium surface with 12 raised longitudinal veins, irregularly papillose especially along veins, dark blue and gradually becoming darker distally but with a narrow whitish collar in the upper part, veins darker than surrounding tissue; inner surface without transverse bars, fenestrated, uniformly translucent dark blue but with a light orange collar in the upper part (above the level of stamen appendages). Annulus almost horizontally covering the hypanthium, dome-shaped, fleshy, milky white, very minutely hairy outside (sometimes apparently glabrous), with roundish triangular orifice ca. 1.5–2.5 mm in diam. Outer tepals spreading, broadly triangular, 1.4–2.4 mm long, 2–3.6 mm wide at base, white and marginally translucent, margin entire, apex acuminate to rounded. Inner tepals distally arching inward and apically broadly fused (inseparable without tearing) to form a thick convex-topped mitre ca. 1.5–3.5(4.5) mm high (excluding free basal tepal parts) and 4–6(6.8) mm wide with prominent sutures and leaving 3 broad arch-shaped lateral apertures 3–4.5 mm wide between mitre, two neighbouring free basal tepal parts and annulus. Inner tepals thick, broadly attached to annulus along its entire radius except its inner margin, basally ca. 2 mm wide, narrowed slightly above to ca. 1 mm wide and broadened towards the mitre. Free parts of inner tepals each with marginal thickenings and with prominent dorsal median keel which continues from one of the hypanthial veins; the keels continue till the mitre top where they prolongate into 3 free erect acute pyramidal appendages 0.5–1 mm high; the appendages initially tightly appressed to each other resembling a short but distinct mucro at the top of mitre, later slightly diverging. Foveae absent. Inner surface of mitre glabrous or more or less hairy especially when young. The narrowest parts of inner tepals outside blackish blue gradually becoming greenish brown basally and white distally; mitre outside milky white except the appendages; the appendages dark to pale blue and later tinged with orange to light brown; inner tepals inside uniformly black including mitre. Stamens ca. 4–5 mm long, with long supraconnectives, fused laterally along their entire length except for the filaments and the rounded apices to form a stamen tube. Each stamen with median longitudinal furrow at the inner (abaxial) side. Supraconnectives bearing skirt-like appendages at the outer (adaxial) side slightly below thecae, concave adaxially below the appendages; each appendage wider than supraconnective, 1.3–1.5 mm wide, inclined towards and reaching the supraconnective apex, with rectangular main lamina and perpendicular marginal wing-like projections of lamina forming H-shaped structure (in bottom view) which are attached to supraconnective tissue so that proximal parts of projections triangularly attenuate towards outside (and decurrent proximally towards the thecae) and distal parts rounded. Thecae adaxial (facing the hypanthium), separate, ca. 1–1.3 mm long. Androecial indumentum of 3–4 papillae at the apex of each supraconnective, stiff long needle-like hairs at the margins of appendages, and 2 rows of shorter glandular hairs on the sides of each theca. Interstaminal glands present. Stamens white except greenish blue distal portions of supraconnectives and translucent light orange appendages. Ovary outside not delimited from hypanthium, obconic, 2.2–3.5 mm long, 2.8–3.8 mm wide towards apex. Placentas column-like. Stylar column shortly cylindrical, ca. 0.4–1 mm long, ca. 0.4–0.9 mm in diam., dark blue; styles ca. 2–3.6 mm below stamen apices, upright, appressed to each other, simple, rectangular, 0.5–1 mm long, bearing densely finely papillose stigmas, translucent light blue.

Etymology: —The specific epithet “ mucronata ” refers to the distinctive mucro at the top of the mitre characteristic of this species.

Phenology: —Flowering from April to June and possibly longer, fruiting since May.

Additional specimens examined: — VIETNAM. Dak Lak Province, Lak District, Bong Krang Municipality, Chu Yang Sin National Park , 10 km S of Krong Kmar village , forest, not far from river, N 12°25’35’’, E 108°21’58’’, 970 m a.s.l., 21 May 2014, M. S. Nuraliev 1009 ( MW) ; same location, 26 May 2019, S. V. Yudina, M. S. Nuraliev 6 ( MW) .

Distribution: —Endemic to Vietnam, where it occurs in two neighbouring provinces: Dak Lak (Chu Yang Sin National Park) and Lam Dong (forestry near Bao Loc town).

Figures

FIGURE 1. Distribution map of the species of Thismia in Cambodia, Laos and Vietnam.

FIGURE 2. Thismia annamensis. A–D. Nuraliev 1562; E–G. Nuraliev 999. H. Nguyen Quoc Dat et al. Pl_Q.NG 0025; all photos by M. Nuraliev except for H by Nguyen Quoc Dat. A. Habit. B, E. Flower, apical view. C. Annulus and stamens, lateral view. D. Flower, longitudinal section. F. Flower with a longitudinal half of hypanthium removed, oblique-bottom view. G. Longitudinal section of distal part of flower showing stamen structure. H. Styles, apical view.

FIGURE 3. Thismia javanica. A–D. Do Thi Xuyen et al. BHH 800, photos by Do Thi Xuyen and SEM image by S. Yudina; E–I. Truong Ba Vuong et al. BV426, photos by Truong Ba Vuong. A, E. Flower, apical view. B, F. Flower, lateral view. C. Longitudinally opened and flattened hypanthium showing stamens. D. Supraconnective, abaxial view (SEM). G. Flower, oblique view. H. Flower with longitudinally opened hypanthium (three stamens removed). I, Three stamens, adaxial view.

FIGURE 4..Thismia mucronata. A, B. Inflorescence, lateral and oblique views. C. Mitre, oblique view. D, E. Young fruit (soon after hypanthium abscission), apical and lateral views. F, G. Excavated root system showing root suckers. All photos by M. Nuraliev from Nuraliev 1009.