Scientific name: Thismia puberula NuralievEnglish name: Vietnamese name: Other name:
VIETNAM. Dak Lak province: Lak district, Bong Krang municipality, Chu Yang Sin national park, 12 km S from Krong Kmar village, in the forest, on an islet of a small river, elevation ca. 1100 m a.s.l., N 12° 23’ 41’’, E 108° 20’ 55’’, 28 May 2014, Nuraliev 1000 (holotype MW!, stored in ethanol).
Plant herbaceous, terrestrial, achlorophyllous, generally glabrous, vegetatively reproducing by formation of root suckers; rhizomes absent. Roots few, clustered at base of stem, vermiform, sometimes branched, thick, Ø 1–1.5 mm. Stem erect or undulating, unbranched, terete and slightly angled, grayish-white, 4–5 cm tall (without terminal flower), Ø ca. 1.5 mm, bearing 1 flower. Leaves ca. 8, alternate, scattered, more or less appressed to stem, scale-like, narrowly triangular, grayish-white and usually brownish towards apex, up to 6–7 mm long. Distal leaves ca. 1.5 mm wide at base, margin entire, apex acute. Leaves become crowded and smaller towards base; basalmost leaves ca. 2 mm long. Involucral bracts 3, inserted ca. 3 mm below ovary and symmetrically arranged around it, subequal, appressed to flower base, similar to upper leaves in size and shape or slightly longer, up to 7.5 mm long, 2 mm wide at base, grayish-white with reddish-brown apex. Flower terminal, actinomorphic, 1.9 cm long from ovary base. Hypanthium obconic, 7–8 mm tall (excluding inferior ovary), ca. 5.8 mm wide in upper part, with 18 veins prominent and raised outside (6 continuing into perianth middle veins with 2 veins between each); involucral bracts reaching one third of hypanthium or less; outer hypanthium surface smooth, dark grayish-brown and gradually becoming darker distally with narrow white collar in upper part, veins slightly darker than surrounding tissue; inner surface without transversal bars, slightly rugose, uniformly brown with white collar with netlike orange thickenings in upper part (above stamen appendages). Perianth of 6 tepals in 2 whorls attached to hypanthium apex. Annulus covering hypanthium to form closed chamber, ca. 2 times broader than tall, dome-shaped with delimited vertical part (wall, 2.5 mm high, slightly rounded outside) and horizontal part (roof, 4.5–5 mm wide) with abrupt right angle between them, fleshy, uniformly covered outside by dense very short hairs; annulus orifice roundish triangular with 3 incisions at radii of inner tepals, Ø ca. 1.5 mm; annulus wall white, roof reddish-orange with gradual transition between them. Outer tepals alternating with involucral bracts, spreading, broadly triangular, 1.5 mm long, 3–3.5 mm wide at base, white, slightly translucent, margin entire, apex acute to acuminate. Inner tepals at same radii with involucral bracts, distally arching inward and apically broadly fused (inseparable without tearing) to form fleshy mitre with prominent furrow-like sutures and leaving 3 broad trapezium-shaped apertures 4–5 mm wide between mitre, two neighboring free basal tepal parts and annulus. Free parts of inner tepals erect, thick, broadly attached to annulus wall along its entire height by ventral keel, basally ca. 2.5–3 mm wide, narrowed slightly above to ca. 1 mm wide, broadened towards mitre and sharply delimited from it; free parts each with marginal thickenings and dorsally raised median vein. Mitre almost round, with straight horizontal lower edges occupying level of annulus apex (making gap scarcely visible from side), 3.5 mm high and 8–8.5 mm wide; inner surface slightly concave and uniformly covered by dense papillate trichomes; outer surface convex with 3 foveae at top alternating with inner tepals and together forming vallate depression ca. 4 mm wide, with median veins slightly prominent below foveae and raised to form crest-shaped borders between foveae; crests connate at mitre centre to form minute tip; outer surface with 2 impressed lateral veins in each tepal at 45º angle to median vein. Inner tepals white with thinner parts translucent except reddish brown central mitre tip. Stamens 6, pendulous from annulus wall and broadly connected to its inner surface by short and thick filaments, ca. 4–5 mm long; base of filaments occupy entire height of annulus; anther connectives dilated, with deep median longitudinal furrow at inner (abaxial) side which continues to filament. Connectives projecting far beyond thecae into apical prolongation, fused laterally with each other along entire length except rounded apices to form stamen tube with 6 narrow holes between free filaments; apical prolongations bearing skirt-like appendages at outer (adaxial) side below thecae, concave adaxially below appendages. Appendages as wide (ca. 1.5 mm) as connective, inclined towards connective apex and not reaching it, with convex quadratic main lamina and perpendicular marginal wing-like projections of lamina forming H-shaped structure (bottom view) attached to connective tissue so that proximal parts of projections shortly triangularly attenuate towards outside and decurrent proximally towards thecae and distal parts narrowly rounded; appendages touching inner surface of hypanthium with distal edge and marginal projections, isolating space between stamen tube and hypanthium, leaving 6 narrow gaps between appendages of adjacent connectives. Thecae 2 per stamen, adaxial (facing hypanthium) on basal part of connective, separate and located near connective margins (immediately below inter-filament gaps and above inter-appendage gaps), narrowly elliptic, longitudinally dehiscent, ca. 1.3 mm long. Androecial indumentum of up to 10 papillae at apex of each connective prolongation, long needle-like hairs along margin of appendages, and 2 rows of shorter glandular hairs on sides of each theca. Interstaminal gland present at each suture of connective fusion, just below thecae, round, smooth, lustrous. Stamens light orange adaxially (outside) including appendages, pale rose abaxially (inside). Ovary inferior, outside not delimited from hypanthium except being white, obconic, 2–2.5 mm long, 3 mm wide towards apex, flat-roofed, unilocular with 3 fusiform central placentas; placentas alternate with stylodia, joined at apex and base of loculus; ovules numerous; stylar column shortly cylindrical, ca. 0.7 mm long, Ø ca. 0.6 mm, dark blue; stylodia 3, ca. 2.7 mm below stamen apices, upright, appressed to each other, simple, rectangular, 1.2 mm long, bearing densely finely papillose stigmas, translucent light blue with brownish apices. Fruit and seeds unknown.
The specific epithet “puberula” means “covered by short hairs” and refers to the presence and nature of the annulus indumentum which differs this species from the most similar ones T. angustimitra, T. mirabilis, T. mucronata and T. okhaensis.
Distribution and habitat
Currently only known from Dak Lak province in Southern Vietnam. The type specimen is represented by a single plant, and despite our intensive search around the area of this collection no more individuals were discovered.
The plant observed in late May possessed a single flower which was in anthetic condition. Besides, a small lateral bud was found in the axil of one of the involucral bracts. It is highly possible that one or more successively blooming flowers develop after the first one, forming a cincinnus, as is known for many other species of Thismia (Stone 1980, Larsen 1987, Maas-Van de Kamer 1998, Larsen & Averyanov 2007, Ho et al. 2009, Tsukaya et al. 2014, Mar & Saunders 2015). We therefore suppose that our collection was made at the very beginning of the flowering season of T. puberula. Such an assumption is also consistent with the observed rarity of this species, as other individuals could probably stay with above-ground shoots not yet fully developed at this time of year and thus could not be spotted.
Flower and fruit biology
Representatives of the genus Thismia are commonly believed to be pollinated by small flies, and recent direct observations are in concordance with this viewpoint (see Mar & Saunders 2015 and references therein). Flower structure of T. puberula is also consistent with this presumed mode of pollination. Interstaminal glands, when present, are frequently described as nectariferous (e.g. Saunders 1996, Thiele & Jordan 2002, Chantanaorrapint & Sridith 2007, Chantanaorrapint 2008, 2012, Chantanaorrapint & Chantanaorrapint 2009, Chiang & Hsieh 2011, Tsukaya & Okada 2012, see also discussion by Mar & Saunders 2015). However, no nectar secretion was detected in T. puberula (our observations) as well as in T. angustimitra and T. mirabilis (S. Chantanaorrapint, pers. comm.). On the other hand, it should be taken into account that examination of the glands is impossible without damage to flower structure, which makes the continuous observations problematic, while the presence of nectar should be checked at various times of the day and different phenological stages.