Thismia papillata Nuraliev & Yudina

Nuraliev, Maxim S., Yudina, Sophia V., Dac, Le Xuan, Kuznetsov, Andrey N., Kuznetsova, Svetlana P. & Semenyuk, Irina I., 2024, Thismia papillata (Thismiaceae), a new species from northern Vietnam, Phytotaxa 655 (3), pp. 261-271 : 262-264

Thismia papillata Nuraliev & Yudina , sp. nov. ( Fig. 1–4 )

Diagnosis:— Thismia papillata is readily distinguishable from most of its congeners by the presence of appendages of outer and inner tepals, inner tepals fused into a mitre, absence of a wing-like appendage of supraconnective and absence of interstaminal glands. The new species is similar to T. abei , T. taiwanensis and T. tuberculata , but differs from them in zygomorphic hypanthium, prominently papillate outer hypanthium surface, very finely papillose (apparently glabrous) annulus, glabrous (or nearly so) tepals, appendages of the outer tepals up to 15 mm long, appendages of the inner tepals up to 9 mm long, column-like placentas, and styles united into a solid pyramidal structure and bearing minute papillae and needle-like hairs.

Type: — VIETNAM. Thanh Hoa Province: Thuong Xuan District, Bat Mot Municipality, Xuan Lien Nature Reserve, forest near stream, periodically flooded, with abundance of herbaceous plants, 19°58.781’N 104°59.068’E, elev. 798 m, 21 October 2023, Semenyuk I. I. s.n. (holotype MW: MW 0595848!).

Etymology: —The specific epithet refers to the pronouncedly papillate appearance of the flower of the new species, which is caused mainly by the papillate hypanthium, and also by the papillae on tepals and their appendages.

Description:—Plant herbaceous, terrestrial, achlorophyllous. Roots vermiform, 0.9–1.0 mm in diam., lacking root hairs. Stem (at anthesis) about 1 mm long, bearing a single terminal flower surrounded by involucre of 3 bracts. Leaves several, scale-like, triangular to ovate, up to 2 mm long, glabrous. Involucral bracts translucent white, obovate, cymbiform, 4.0– 4.9 mm long, glabrous, tightly appressed to flower base. Pedicel (internode between involucral bracts and ovary) less than 1 mm long. Flower zygomorphic due to hypanthium shape, uniformly translucent white, ca. 13 mm high from ovary base. Hypanthium obliquely obconic-obovate, in the middle bent at approximately 90°; ovary and proximal portion of hypanthium arranged more or less horizontally (parallel to the ground), remaining part of flower erect (vertically oriented); hypanthium 5.5 mm high at the shortest side and 8.5 mm high at the longest side (excluding inferior ovary), ca. 7 mm in diam. in the upper part; involucral bracts reaching ovary top or the very base of hypanthium. Outer hypanthium surface with 12 longitudinal veins (visible in spirit), papillate throughout; in distal portion of hypanthium each papilla terminating into a hair. Inner hypanthium surface slightly rugose, without transverse bars or cavities, glabrous. Annulus prominent, circular to indistinctly hexagonal, rim-shaped, ca. 4.5 mm in diam., with prominently revolute outer margin, densely covered with very fine papillae, with circular orifice ca. 3.5 mm in diam. Perianth of 6 tepals in 2 alternating whorls, attached to hypanthium top. Outer tepals alternating with involucral bracts, spreading, thin, broadly triangular, seemingly narrowly triangular due to drooping margins, 3.2–3.3 mm long, 2.5–2.6 mm wide at base, margin slightly irregular, apex acute, glabrous or with several papillae on abaxial side, with midvein strongly raised abaxially and continuing into a filiform appendage, with a minute triangular tip of tepal blade free from the appendage lying above the appendage base; appendages straight, up to 15.5 mm long, with several papillae in basal part. Inner tepals spathulate, distally arching inward and broadly fused (inseparable without tearing) in imbricate aestivation to form a mitre and leaving 3 broad arch-shaped lateral apertures ca. 2 mm high and ca. 5 mm wide between mitre, two neighboring free basal tepal parts and hypanthium top. Tepal margins slightly irregular within mitre and entire in free tepal parts. Free parts of inner tepals erect, slightly fleshy, attached to hypanthium top by thick base, basally ca. 1.5 mm wide, with revolute margins, not distinctly delimited from mitre, slightly papillate externally (abaxially) below appendages and glabrous internally (adaxially); each free tepal part dorsally bearing a filiform appendage attached at middle of its length in form of abaxially raised midvein; appendages up to 8.8 mm long, sparsely papillate (especially towards base). Mitre thin (not fleshy), slightly convex, approximately 2.5 mm high and 5 mm in diam., glabrous, with free margins of tepals around the fusion areas; distal portion of inner tepal (within mitre) ca. 3.5 mm wide. Stamens 6, pendulous from annulus, 2.6–3.0 mm long, with long supraconnectives, fused laterally along their entire length except for the filaments and distal (bent) portions of supraconnectives into stamen tube. Filament ca. 1 mm long, ca. 0.8 mm wide, with U-shaped base (at attachment to annulus). Supraconnective fleshy, nearly rectangular, ca. 1.0– 1.4 mm long, ca. 1.2 mm wide, boot-shaped, i.e. with the distal half bent at 90° towards the hypanthium (or more or less inclined downwards), with heel-like swelling at point of bending (at inner side), with entire rounded apex, without appendages. Thecae 2 per stamen, adaxial (facing the hypanthium), separate, parallel, extrorse, ca. 0.7 mm long; each microsporangium narrowly elliptic, longitudinally dehiscent; in each theca, the inner microsporangium (facing the stamen midvein) arranged slightly higher than the outer one (facing the stamen margin). Androecial indumentum of a row of 10–11 down-pointing needle-like hairs ca. 0.8 mm long at heel-like swelling of each supraconnective, shorter hairs on distal portions of supraconnectives, and 2 rows of short glandular hairs on the sides of each theca. Interstaminal glands absent. Ovary inferior, outside not delimited from hypanthium, obconic, ca. 2.1 mm high, 2.8 mm in diam. towards apex, minutely papillate, flat-roofed, unilocular. Placentas 3, column-like, central, alternating with styles, attached to base and roof of ovary; ovules numerous, white. Stylar column cylindrical, ca 1 mm high, ca. 0.5 mm in diam., glabrous, terminating into pyramidal structure. Pyramidal structure ca. 2 mm high, of 3 radially flattened parts united along central axis, each part likely corresponding to a style; each style at base with a pair of ovate thickenings with scabrous-papillose surface (each pair presumably being a stigma), with one lateral and one apical triangular extension, tips of both extensions bearing minute papillae and needle-like hairs ca. 0.5–0.7 mm long. Fruit and seeds unknown.

Phenology: —Flowering in October.

Distribution and ecology: — Thismia papillata is currently known from a single location in Xuan Lien Nature Reserve, Vietnam. The species inhabits primary submontane forest at elevation of 800 m a.s.l., where it occurs along small streams. 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.

Figures

FIGURE 1. Thismia papillata. A, B. Plant in natural habitat. C. Flower, view from above. D, E. Flower, side-top view. F, G. Flower, side view. Some of the tepal appendages were damaged. Semenyuk s.n.; photos by I.I. Semenyuk.

FIGURE 2. Thismia papillata: two stamens artificially detached from the neighboring stamens (spirit material). Semenyuk s.n.; photos taken by S.V. Yudina using a dissecting microscope.

FIGURE 3. Thismia papillata. A. Flower, side view. B. Flower, view from above. Drawn from Semenyuk s.n. by I.I. Semenyuk.

FIGURE 4. Thismia papillata. A. Flowering shoot. B. Longitudinally dissected flower (outer tepal and appendage of inner tepal not shown). C. Flattened inner tepal, abaxial view. D. Flattened portion of stamen tube, view from outside. E. Stylar column and styles. Drawn from Semenyuk s.n. by S.V. Yudina.