Arisaema langbiangense Luu

Van, Hong Thien, Nguyen-Phi, Nga & Luu, Hong Truong, 2016, A new species of Arisaema (Araceae) from Vietnam, Phytotaxa 277 (1), pp. 90-94 : 90-92

Arisaema langbiangense Luu , Nguyen-phi & H.T. Van , sp. nov. ( Fig. 1 )

Allied to A. bannaense , A. claviforme , A. garrettii and A. petiolulatum but different in having green flesh of rhizome, long pseudostem, forwards bent spadix appendix and 5(6)-lobed obovoid ovaries.

Type:— VIETNAM. Lam Dong Province, Lac Duong District, Bidoup-Nui Ba National Park, Langbiang Mountain, about 108026 ’58’’ E, 1200 ’29’’ N, 1702 m in elevation, 18 January 2014, Van Hong Thien H.T.Van 06 (holotype SGN!, isotypes SGN! & PHH!).

Recommended Vietnamese name: ––Nam tinh Langbiang

Herb evergreen, 30–55 cm high. Stem a subterranean cylindrical rhizome, 5–9 cm long, 1.5–2 cm wide, whitegrey outside, green inside. Cataphylls 2–4, greenish brown, reddish brown mottled, 20–22 cm long. Leaf: 1 to 3; the last petiole and peduncle sheathing into pseudostem (sensu Gusman & Gusman, 2006) at lower part, free above; pseudostem 22–26 cm long, greenish brown, reddish brown mottled; free part of the petiole 9–11 cm long, brownish green with spare reddish brown mottling. Leaf blade trifoliolate, leaflets equal in size, 14–16 cm long, 7–10 cm wide, dark green above, pale green under side, apex acuminate with up to 2 cm, caudate tip, midrib impressed adaxially and prominent abaxially, lateral veins diverging from the midrib and collective vein at ca. 0.3 cm from margin, central leaflet ovate, with base rounded, petiolule ca. 2 cm long, lateral leaflets asymmetrical, with base rounded, petiolule ca. 0.8 cm long. Inflorescence solitary; free part of the peduncle 18–20 cm long, ca. 1 cm in diameter, green, with sparse reddish brown mottling; spathe tube cylindrical, green, 7–9 cm long, ca. 1 cm in diameter; spathe limb ovate, curved over mouth, 4–5 cm long, 2.5–3 cm wide, green, translucent, ending in a ca. 1 cm caudate tip. Male spadix 6–7 cm long; appendix slightly exserted from tube mouth, 3.5–4 cm long, naked, ca. 0.4 cm in diameter at base, ca. 0.2 cm in diameter at apex, green, cylindrical, apex round and smooth; male zone 2.5–3 cm long, synandrium of 2 or seldom 3 stamens, loosely arranged, on a ca. 2 mm long stipe; thecae purple or cream with purple top and dehiscent by dark purple round pore at anthesis. Bisexual spadix 5.5–6.0 cm long; appendix slightly exserted from tube mouth, 1–1.5 cm long, naked, ca. 0.4 cm in diameter at base, ca. 0.2 cm in diameter at apex, cylindrical, apex round and smooth; female zone ca. 1.5 cm long, 0.5–1 cm in diameter, ovaries obovoid, green, 5(6)-lobed, ca. 2 mm in diameter, 1-locular, with 3–4 bottle-shaped ovules, densely arranged; stigma born on a thick 1 mm long style; male zone ca. 2 cm long, synandrium of 2 or seldom 3 stamens, loosely arranged, on a 1–2 mm long stipe; thecae horseshoe-shaped, cream with purple top and dehiscent by dark purple round pore at anthesis.

Habitat: –– Arisaema langbiangense grows on humus and wet places under tropical evergreen forest at elevations of around 1,700 m.

Eponymy:—The new species is named after its type location, Langbiang Mountain.

Distribution: –– Arisaema langbiangense is only known from the type location.

Taxonomic discussion: –– Arisaema langbiangense obviously belongs to section Anomala and it is most closely relative to A. bannaense H. Li (1988: 101) , A. claviforme , A. garrettii and A. petiolulatum , in having: evergreen habit, subterranean rhizomatous stem, trifoliolate leaf and fleshy spadix appendix with naked apex slightly exserted from the tube mouth. However, it is distinct in having green flesh of its rhizome - an attribute first reported for the genus, long pseudostem, forwards bent spadix appendix and 5(rarely 6)-lobed obovoid ovaries ( Table 1). In addition, it can be distinguished from A. bannaense and A. garrettii in having ovate spathe limb without strong constriction at base and more slender spadix appendix. It is different from A. claviforme as the latter has an obviously club-shaped spadix appendix, inconspicuous pseudostem and 3 to 4-androus synandria. Arisaema petiolulatum differs from the proposed new species in having one leaf with elliptic central leaflet, unmottled petiole, spathe limb with strong constriction at base and thecae opened by an apical slit ( Pham-hoang, 2000; Gusman & Gusman 2006; Li et al., 2010). All the other species of the section known from Vietnam are readily distinguishable from the new species as they have filiform bristles on the spadix appendix.

Figures

FIGURE 1. Arisaema langbiangense. A. Habit. B. Pseudostem. C. Leaf blade. D. Rhizome section. E. Spathe. F. Male spadix. G. Bisexual spadix. H. Ovaries. I. Synandria. J. Longitudinal section of ovary. K. Cross section of ovary.