Typhonium vietnamense Luu, Nguyen-Phi & H. T. Van 2021, sp. nov.

Typhonium vietnamense Luu, Nguyen-Phi & H.T.Van, sp. nov. (Figs. 1, 2)

The new species is most morphologically similar to Typhonium varians Hett. & Sookchaloem in Hetterscheid et al. (2001: 51) in variant shape of leaves, triangular ovate spathe limb and general florescence structure but differs from the latter in having plain green (vs. variegated) leaves, underground (vs. above ground) flowering spathe tube, abaxially reddish purple to greenish grey, brownish mottled and ascending (vs. dark green flushed with dirty brown and horizontal) spathe limb, erect (vs. ascending) spadix, bright yellow staminodes curved downwards at their tips only (vs. pale yellow staminodes curved upwards or downwards over their entire length), ovoid (vs. spathulate to pyriform) fruits and generally smaller floral parts (3.5–4.5 vs. 8.0– 13.5 cm long spadix, 3.5–5.0 × 2.0–2.5 vs. 7–14 × 4.0– 7.5 cm spathe limb, 2.0–3.5 × 0.4–0.5 vs. 4.5–9.0 × 0.6–1.0 cm spadix appendix).

Type:— VIETNAM. Ba Ria - Vung Tau Province: Binh Chau - Phuoc Buu Nature Reserve, about 107 o 30’52’’E, 10 o 36’17’’N, 30 m elevation, 05 August 2015, Le Van Son, Nguyen Phi Nga & Van Hong Thien H. T.Van 115 (holotype SGN!, isotypes PHH!, VNMN!).

Herb seasonally dormant; rhizome tuberous, subglobose to ellipsoid, underground, 1.0– 1.5 cm long, ca. 1 cm in diameter, producing many thick roots. Leaves 4–5. Petiole smooth, slender, 7–15 cm long, 2–3 mm in diameter, white to grey with brownish mottled at base, green towards the apex. Leaf blades entire or pedatisect, green above, pale green beneath; entire blades linear, deltoid to lanceolate, 6–10 cm long, 2–8 cm wide, with acuminate to obtuse apex; pedatisect blades with 3 to 5 linear to lanceolate segments (up to 15 cm long, 2.0– 4.5 cm wide). Inflorescence, solitary (rarely 2), slightly foetid smelling; peduncle underground, elongated in fruiting, white, 1.5–2.0 cm long, ca. 3–5 mm in diameter; spathe 4.5–6.0 cm long; spathe tube underground, separated from the limb by a constriction, ovoid or ellipsoid, 1.3–1.7 cm long, 9–10 mm wide, outside white with brownish dots, inside white to pale pink; spathe limb triangular ovate, 3.5–5.0 cm long, 2.0– 2.5 cm wide, outside reddish purple to greenish grey, brownish mottled, inside dark purple to reddish purple; spadix little shorter than spathe, sessile, erect; female zone conical, 2–3 mm high, ca. 5 mm in diameter at base, with 6–7 rows of crowded pistils; ovary obovoid or slightly cylindrical, 1 mm high, 0.7 mm in diameter, translucent white with brownish dots at apex, 1-locular, with 1 basal ovule; style very short; stigma disciform, thick, 0.6 mm in diameter, 0.3 mm high, blackish purple to pink, papillate; sterile zone contiguously female zone, 8–10 mm long, lower part covered with 3–4 rows of staminodes, upper part naked; staminodes bright yellow, subulate, 2–3 mm long, ca. 0.5 mm in diameter, ascending forming an obtuse angle with the spadix axis, slightly curved downward, weakly papillose; male zone cylindrical, 6–10 mm long, 3.5–5.0 mm in diameter; stamens densely arranged, pale yellow to pink; thecae opening by elongate slit; appendix shortly stipitate, outside brownish purple to reddish, inside light yellow, elongate conical, 2.0– 3.5 cm long, 4–5 mm in diameter at base, with acute apex and truncate base. Infructescence obconical with spathe tube remaining and above the ground; fruits obconical, pinkish white with pale pinkish spots, 4–7 mm long, 2–3 mm wide, 1-seeded; seed obovate (or having constriction), at first creamy white, light brown when mature, 3.0– 3.5 mm long, 2.0– 2.5 mm wide.

Etymology: —The species is named after Vietnam, the country of origin.

Vietnamese name: —Bán hạ Việt Nam.

Ecology: —The new species grows in clumps on open sandy soil in sparse dipterocarp-dominated forests. Different leaf forms were found in plant individuals or clumps. Flowering was seen in May to June and fruiting in July to August. The plant becomes dormant in November to April next year.

Additional specimen examined (paratype):— VIETNAM. Dak Lak Province: Yok Don National Park, 01 October 2015, Nguyen Le Xuan Bach & Van Hong Thien H . T.Van 126 (SGN!).

Distribution: —Ba Ria - Vung Tau Province and Dak Lak Province, southern Vietnam.

Proposed IUCN conservation status: — Data Deficient (DD) (IUCN Standards and Petitions Subcommittee 2017). Typhonium vietnamense has so far been found in two protected areas (Binh Chau - Phuoc Buu Nature Reserve, Ba Ria - Vung Tau Province and Yok Don National Park, Dak Lak Province) in southern Vietnam. Although its habitat in Binh Chau - Phuoc Buu Nature Reserve is planned to be converted into a resort in the near future, the species is likely to occur in adjacent similar sparse dipterocarp-dominated forests in Cambodia. Further survey work is necessary before a definitive conservation assessment can be made.

Notes: —The new species is morphologically closest to Typhonium varians but they have a number of differences as expressed in the diagnosis. Several other Typhonium species share with T. vietnamense a similar spadix structure, especially in the shape of spadix appendix and staminodes, but these are easily distinguishable: T. conchiforme Hetterscheid & Galloway (2006: 80) by deeply sagittate leaf blades, deeply cymbiform, strongly concave spathe limb and off-white or pale yellow staminodes; T. sagittariifolium Gagnepain (1942b: 11) by deeply trilobed sagittate leaf blades, erect elongate triangular spathe limb, longer spadix appendix (8 mm), and longer (3–5 mm) and recurved staminodes; and Typhonium viridispathum Galloway & Sinhabaedya (2012: 61) by bright green spathe with elongate triangular limb, off-white spadix appendix, basally white and apically pale green ovaries and white staminodes.