Rohdea extrorsandra N.Odyuo, D.K.Roy & Aver., 2017

Odyuo, N., Roy, Dilip Kr. & Averyanov, Leonid V., 2017, Rohdea extrorsandra (Asparagaceae), a new species from north-eastern India, Phytotaxa 309 (3), pp. 283-287 : 283-286

Rohdea extrorsandra N.Odyuo, D.K.Roy & Aver. , sp. nov. ( Figs. 1 , 2 )

Differs from all known taxa of the genus Rohdea Roth in having strongly inflexed perianth segments, erect stamens with distinct free filaments and extrorse anthers.

Type:— INDIA. Dampa Tiger Reserve, Tuichar stream banks in Dampa Hill, Mizoram, 25 September 2016 ex hort. in Garden of Botanical Survey of India (Eastern Regional Centre, Meghalaya, East Khasi Hills, Shillong, Woodland Campus), N. Odyuo 117300 (holotype, ASSAM!, isotype CAL!).

Terrestrial perennial herb. Rhizomatous stem erect, 25–35 cm long, thick, fleshy, 2–2.5 cm in diam., terete, simple, white or dull creamy-white inside, with distinct nodes and internodes. Roots tuft, arising from only one side of rhizomatous stem, to 5 mm in diam., light grey velutinous. Leaves 2–3, distinctly petiolate; petiole thick, channelled adaxially, 20–43 cm long; leaf blade oblanceolate, 130–185 × 11.5–13.5 cm, leathery, glabrous, uniformly glossy green, with distinct midvein, base gradually tapering, apex shortly acuminate. Inflorescences axillary in apical part of rhizomatous stem, subtended by 3–4 sheath leaves; sheath leaves ensiform, conduplicate, 18–36 × 1–3 cm, glabrous; peduncle erect, straight, rigid, glabrous, 35–60 cm long, 5–7 mm in diam., semi-circular in cross section; spike densely many flowered, 5–10 cm long, 1.5–1.7 cm in diam., simple, with few sterile bracts apically. Fertile bract 1 per flower, ovate-triangular, 0.4–4.2 cm long, 3.8–4 mm wide, slightly concave at the base, shorter than the flower, triangular obtuse at the apex, green, with white membranous, sparsely dentate margin. Flowers sessile, 1.3–1.5 cm in diameter. Perianth urceolate, very thick, fleshy, greenish when young, later turning to light creamy-pink outside, light creamy, tinged with purple inside, 6–7 mm long, 9–11 mm wide, proximal syntepalous part 1.5–2 mm long; distal perianth part 6-lobed; lobes not spreading, strongly inflexed, thick, triangular, 2.5–4 × 2–3 mm, ridged inside, smooth outside, acute at apex. Stamens 6, free, arising from median part of perianth tube; filaments erect, straight, ca. 1.5 mm long; anthers ellipsoid, 1–1.2 mm long, 0.8–1 mm wide, pale-yellow, dorsifixed, extrorse, with short appendage, overtopping the stigma. Pistil 1; style very short, inconspicuous; stigma 3-lobed, each lobe ovate to almost half-circular, curved abaxially downwards. Ovary superior, subglobose, 2–2.5 mm wide, light green, 3-loculed; each locule containing 2(3) obovoid ovules on basal placenta. Fruit berry-like, subglobose, dark brown, irregularly tuberculate, 2–2.3 cm wide, without persistent remnant of the style at apex.

Phenology:— Flowering from August to September. Initial development of fruits was observed from September to December and they were matured in April.

Etymology:— The specific epithet refers to the extrorse anthers, which is the most significant character differentiating the species from all known congeners.

Habitat:— The new species was found growing on the banks of stream in tropical wet semi-evergreen forests. The soil texture varies from sandy loam to clay loam. The forests are of medium stature with tree height reaching up to 25 m.

Distribution:— INDIA. Mizoram (Dampa Tiger Reserve). So far only known from the type locality (banks of Tuichar stream in Dampa Hill).

Taxonomic relationship:— The comparison of morphology among all known species of Rohdea indicates that R. extrorsandra superficially resembles to R. longipedunculata ( Wang & Liang 1978: 249) Tanaka (2003: 332) . However, R. extrosandra differs from R. longipedunculata by the large leathery, oblanceolate leaf blade, 130–185 cm long and 11.5–13.5 cm wide (vs. herbaceous or subleathery, linear-oblanceolate, 40–80 cm long and 3–6.5 cm wide), 1 bract per flower (vs. 2), strongly inflexed, triangular perianth segments, 2.5–4 mm long, 2–3 mm wide (vs. almost erect to incurved, deltoid-ovate, 2–2.5 mm long, 1.5–2.5 mm wide ( Fig. 3A )), stamens with erect filaments located in the median part of the perianth tube (vs. with incurved filaments located at the throat of the perianth tube ( Fig. 3B )), extrorse anthers, with appendage (vs. introrse, without appendage ( Fig. 3B )), inconspicuous style, much shorter than 1 mm long (vs. distinct, about 1.5 mm long ( Fig. 3C )), distinctly 3-lobed stigma, each lobe ovate to half circular (vs. obscurely 3-lobed, to subcapitate ( Fig. 3C )).

Figures

FIGURE 1. Rohdea extrorsandra. A-C. Plant in nature. D, E. Rhizomatous stem with roots. [Image design by D.K. Roy].

FIGURE 2. Rohdea extrorsandra. A. Spike. B. Spike apex. C. Spike cross section, view from above. D. Floral bract, adaxial surface. E. Flower, frontal view. F. Flower, sagittal section. G. Transversal section of perianth tube, with stamens. H. Sagittal section of perianth, with stamens. I. Stamens, side view. J. Pistil. K. Ovary. L. Ovary, transversal section. M. Ovules. N. Fruit. [Image design by D.K. Roy].

FIGURE 3. Flower of Rohdea longipedunculata. A. Frontal view, B. Sagittal perianth section, C. Pistil, side view (A-C of the same scale), adopted from Tanaka (2003).