Peliosanthes longiracemosa K.S.Nguyen, N.Tanaka & Aver., 2021

Nguyen, Khang Sinh, Tanaka, Noriyuki, Averyanov, Leonid V., Nguyen, Thanh Son & Pham, Van The, 2021, Peliosanthes longiracemosa (Asparagaceae), a new species from limestone areas of northern Vietnam, Phytotaxa 514 (2), pp. 173-179 : 174-177

Peliosanthes longiracemosa K.S.Nguyen, N.Tanaka & Aver. , sp.nov. ( Figs. 1 , 2 )

Most similar to P. macrostegia in having a distally incurved corona and a distinct pyramidal style, but differs mainly in the wider leaf blades with more longitudinal veins and closer transverse veinlets, relatively longer, more slender raceme, more numerous, widely expanded flowers with strongly recurved, laterally revolute perianth segments, and more incrassate, depressed globose staminal corona.

Type: — VIETNAM. Tuyen Quang Province, Na Hang District, Sinh Long Commune, Nam Duong Village , Xo Lo Che area , in remnants of primary evergreen broard-leaved forest on steep slopes of limestone mountain, along stream, 500–550 m a.s.l., around point 22 o 35’28”N, 105 o 21’20”E, terrestrial or lithophytic perennial herb up to 65 cm tall, flowers pale greenish to light yellow-orange, locally common, 25 October 2020, Nguyen Sinh Khang, Nguyen Thanh Son, Pham Van The & Ban Van Dan, NSK 1366 (holotype: HN!, isotypes: HN!)

Description: ― Herb terrestrial or lithophytic, acaulescent, rhizomatous, evergreen, perennial. Rhizome creeping, subterete, (2.5–)3–5.5(–6) cm long, (6–)7–9(–11) mm in diam., simple, robust, light brownish grey, producing several roots. Roots cordlike, rigid, semi-ligneous, (3–)7–20(–25) cm long, (1.5–) 2–3 mm in diameter. Sheath leaves (cataphylls) 5–7 at base of leaf petiole and floriferous stem, imbricate, nearly deltoid, ovate, lanceolate, linear-lanceolate or ensiform, (0.5–)2.5–13(–15.5) cm long, (8–)9–13(–15) mm wide (when flattened), subacute or blunt, concave or convolute, longitudinally veined, chartaceous, dark purple or almost blackish violet, margins dull white and scarious, persistent during anthesis, later disintegrated into fibrous remains. Leaves basal, (1–)2–4(–5), borne at intervals of (8–)9–13(–15) mm; petioles rigid, straight or nearly so, (30–)40–50(–55) cm long, (3.5–)5(–5.5) mm in diam., shallowly grooved adaxially; blades elliptic or elliptic oblanceolate, (22–)27–35(–37) cm long, (7.5–)8.5–12.5(–14.5) cm wide, base attenuate, margins minutely denticulate, apex shortly acuminate, longitudinally subplicate, adaxially green and glossy, abaxially paler, longitudinal veins (22–)26–30(–38), transverse veinlets numerous, perpendicular or oblique to longitudinal veins, lying close to one another with intervals ca. 0.7–0.9 mm. Flowering stem (including peduncle and inflorescence rachis) 1–2, arising from apical portion of rhizome (stem), slender, arching, usually longer than leaf blade, (35–)40–55(–62) cm long, dark purple or blackish violet. Peduncle terete, (6–)9–14(–17) cm long, (2.5–)3–3.5(–4) mm in diam., apically bracteate; sterile bracts (1–)2–3(–4), embracing peduncle, antrorse, cymbiform, narrowly deltoid, (7–)9–15(–17) mm long, (3–)3.5–5.5(–6) mm wide at base, margins membranous, entire, almost flat or weakly undulate, apex acuminate. Inflorescence racemose, many-flowered, (25–)30–50(–55) cm long, much longer than peduncle (at least 2.5 times longer), tapering toward apex, 2.5–3.5 mm wide at base, 0.5–0.7 mm in diam. in apical part, longitudinally slightly ridged, pentagonal to orbicular in cross section. Pedicels straight and ascending or curved downward, terete, (5–)6–9(–11) mm long, (0.4–)0.5–0.6(–0.7) mm in diam., dark purple to blackish violet. Floral bracts 2 at basal portion of pedicel, unequal in shape, size and position, antrorse, cymbiform, unicostate, scarious, purple to blackish violet, midvein usually greenish, margins nearly flat or somewhat undulate; the outer (lower) bract narrowly deltoid to triangular lanceolate, (4.5–)5.5–10.5(–11.5) mm long, (1.8–)2–3(–3.2) mm wide near base, acute, acuminate or caudate at apex; the inner smaller bract (bracteole) subulate, lanceolate or narrowly ovate, (1.8–)2–2.5(– 2.8) mm long, (0.8–)0.9–1.3(–1.5) mm wide, acute to acuminate. Flowers (65–)100–120(–130) per rachis, acropetally blooming, solitary in axils of bracts, obliquely antrorse or retrorse, (7.5–)8–8.5(–9) mm in diam.; perianth 6-cleft, light bluish green to dull pale orangey green, sometimes sparsely speckled with purple or violet; proximal tubular part funnel-shaped, (2.6–)2.7–3(–3.1) mm in diam., (1.5–)1.6–1.7(–1.8) mm high; perianth segments 6 in 2 whorls of 3, ovate to oblong, (3–)3.2–3.8(–4) mm long, (1.8–)2–2.5(–2.7) mm wide, recurved, adaxially slightly convex, margins entire, flat or slightly undulate, revolute, apex blunt to nearly rounded. Stamens 6, monadelphous, united filaments forming a corona which is depressed globose with broadest portion at or slightly below the middle, hexagonal to nearly rotund, (2.8–)3–3.6(–3.8) mm in diam., (1.3–)1.4–1.6(–1.7) mm high, fleshy, incrassate, light bluish green to pale greenish yellow, later turning to light (brownish) orange, inside obtusely slightly ribbed, the wall up to ca. 1 mm thick around middle; orifice shallowly 6-lobed, (1.4–)1.5–2(–2.1) mm in diam.; anthers broadly elliptic or rotund, 0.6–0.8 mm long, 0.5–0.6 mm wide, dorsally attached to distal inside of staminal corona, bilocular, introrse, creamy to pale orange. Pistil 1, tricarpellate, subconoid, half-inferior, exposed portion (1.2–)1.3–1.5(–1.6) mm high (whole height including the sunken part: (1.7–)1.8–2(–2.1) mm), pale greenish-yellow, proximally speckled with dirty purple or violet; ovary trilocular, distal exposed portion pyramidal and hexagonal, 1.3–1.6 mm in diam. at base; ovules (2–)4 per locule, borne at base of central axis of ovary, suberect, oblong; style distinct, conoid or pyramidal, truncate at stigmatic portion, 1.2–1.4 mm long, 0.6–0.8 mm wide at base, 3-sulcate; stigma tripartite, ca. 0.4 mm wide, lobes almost explanate, oblong, 0.25–0.3 × 0.1–0.13 mm, ventral side centrally grooved, finely papillose. Immature seeds 1–2 per flower, pyriform, 15–17 mm long, 8–10 mm in diam., testa green, glossy.

Paratypes: — VIETNAM. Tuyen Quang Province: Na Hang District, Sinh Long Commune, Na Tau Village , in selectively logged primary evergreen broad-leaved forest, along stream bank of limestone mountain, 300–350 m a.s.l., around point 22 o 34’22”N, 105 o 23’25”E, terrestrial or lithophytic perennial herb, flowers pale greenish, not rare, 27 September 2011, Nguyen Tien Hiep, Nguyen Sinh Khang, Pham Van The & Nguyen Tien Vinh, CPC4509 ( Herbarium of Center for Plant Conservation, Hano) ;— VIETNAM. Tiuyen Quang Province: Na Hang District, Sinh Long Commune, Nam Duong Village , in humid, wet places in remnants of evergreen broad-leaved forest at foot of limestone mountain Phim Panh , 500–540 m a.s.l., around point 22 o 34’28”N, 105 o 22’04”E, terrestrial herb up to 60 cm tall, cataphylls (sheath leaves) and inflorescences dark purple or black violet, occasional, 06 October 2017, Nguyen Tien Hiep, Nguyen Sinh Khang, Chuong Quang Ngan, Nguyen Quang Hieu, Ban Van Dan & Ban Van Phat, CPC8347 ( HN) .

Etymology: —The specific epithet refers to the long racemose inflorescence.

Phenology: —Flowering from September through late October, fruiting in October through November.

Distribution and habitat: —The new species is currently known only from Sinh Long Commune in Na Hang District, Tuyen Quang Province, northern Vietnam, where it was occasional or common in occurrence. It grew on rocks or ground in shady humid locations in evergreen broad-leaved forests developed on slopes of limestone mountains at elevations 300–550 m a.s.l. On the forest floor it co-occurred with such species as Ophiorrhiza amplifolia , Mycetia sp. , Spiradiclis sp. (Rubiaceae) , Lysionotus sp. , Primulina sp. , Paraboea spp. (Gesneriaceae) , Mitreola sp. (Loganiaceae) , Elatostemma spp. , Pilea spp. (Urticaceae) , Begonia rhytidophylla , Begonia spp. (Begoniaceae) , Ophiopogon latifolius , Ophiopogon dracaenoides , Aspidistra spp. (Asparagaceae) , Schizocapsa plantaginea , Tacca chantrieri (Taccaceae) , Arisaema sp. (Araceae) , Pteris spp. (Pteridaceae) , Tectaria spp. (Tectariaceae) , etc. To properly assess the conservation status of the new species, we need to conduct further field research on its distribution in other regions.

Taxonomic relationships: — Peliosanthes longiracemosa here described is somewhat similar to P. macrostegia in having a distally incurved staminal corona and a pistil with a distinct pyramidal style, but clearly distinguishable mainly by the wider (7.5–14.5 vs. up to ca. 8 cm) leaf blade usually with more longitudinal veins (22–38 vs. 13–28) and denser, closer transverse veinlets, relatively longer, more slender raceme, more numerous (65–130 vs. up to ca. 50), widely expanding flowers with strongly recurved, laterally revolute (vs. usually incurved) perianth segments, and more incrassate, depressed globose (vs. dome-shaped) staminal corona broadest at or slightly below the middle (vs. at or near the base). Since such an unusually long slender raceme and strongly recurved perianth segments are regarded as specialized or apomorphies compared to the moderately long raceme and less expanded perianth segments, it is likely that P. longiracemosa is a more advanced species in these respects than P. macrostegia and diverged from the ancestor of the latter in the course of evolution.

In having large leaves and incrassate incurved staminal coronas, the new species may also look similar to P. crassicoronata K.S. Nguyen, Aver. & N. Tanaka in Nguyen et al. (2020: 41) known from southern Vietnam, but is evidently distinct chiefly in the greenish or pale orangey (vs. purplish) perianth and corona, widely expanding, recurved (vs. incurved) perianth segments, depressed globose (vs. dome-shaped or hemispheric) corona, and pistil with a half-inferior (vs. almost superior) ovary and a distinct pyramidal (vs. indistinct) style. Some key morphological characters of these three species are compared in Table 1.

Figures

FIGURE 1. Peliosanthes longiracemosa. A. Habit of plant in natural habitat. B. Basal portion of plant with rhizome, roots and sheath leaves. C. Habit of plant, flattened. D. Leaf blade, adaxial view. E. Portion of leaf blade, adaxial surface. F. Leaf margin, abaxial side. G & H. Portions of racemes. Photos and layout by K.S. Nguyen. A–F & H: NSK1366, G: CPC4509.

FIGURE 2. Peliosanthes longiracemosa (NSK1366). A. Portion of inflorescence. B. Flower; back view. C. Flower, front view. D. Front view of central part of flower with staminal corona cross-cut. E. Exposed portion of pistil. F. Portion of flower longitudinally cut, showing shape of pistil and corona. Photos and layout by K.S. Nguyen.