Rhapis kebangensis Henderson, 2016

Henderson, Andrew, 2016, A revision of Rhapis (Arecaceae), Phytotaxa 258 (2), pp. 137-152 : 144

5. Rhapis kebangensis Henderson sp. nov. Type:— VIETNAM. Quang Binh: Ba Trach district, Phong Nga-Ke Bang National Park, 17°23’N, 106°13’E, 650 m,. 20 October 2015, A. Henderson & Nguyen Quoc Dung 4048 (holotype FIPI!, isotype NY!). ( Fig. 3 )

Stems 0.6 m long, 0.4(0.3–0.4) cm diameter. Leaf ligules lobed, more or less persistent; petioles 13.2(10.0–17.7) cm long, 0.9(0.8–1.1) mm wide at the apex; abaxial hastula usually incomplete, part of the petiole continuous with the costa; segments 4(3–4) per leaf; central segments lanceolate or elliptic, usually multi-veined, acuminate, the apices oblique, toothed, 12.7(10.9–16.5) cm long, 1.9(1.5–2.2) cm wide at midpoint, free almost to the base, the non-split basal part 0.3(0.3–0.4) cm; lateral segments 12.1(10.5–15.5) cm long, 0.7(0.5–0.9) cm wide at midpoint, the non-split basal part 0.3(0.2–0.3) cm; abaxial surface of segments without scales, gray indumentose when first exposed. Inflorescences slender, few branched, with the first branch not as large as the rest of the inflorescence; prophyll and peduncular bract narrow, tubular, not or scarcely overlapping, the inflorescences exerted apically through the bracts on a curved peduncle; rachis 2.4(2.2–2.5) cm long; rachillae not filiform, glabrous; proximal rachilla 5.6(4.7–6.5) cm long, 0.8(0.6–0.9) mm wide; staminate and pistillate flowers sessile; staminate and pistillate corollas with well developed, erect, triangular apical lobes, these swollen internally; filaments terete; fruits globose, color not recorded, 7.8(5.6–9.9) mm long, 5.7(4.8–6.6) mm diameter, borne on a swollen, persistent perianth.

Distribution and habitat:— Vietnam (Quang Binh)( Fig. 4 ) at the base of steep, limestone cliffs at 593(450–680) m elevation.

Taxonomic notes:— Rhapis kebangensis is unique in the genus by its segments with the abaxial surface gray indumentose when first exposed. The swollen, persistent perianth of this species is much more developed than those of similar species (e.g., R. subtilis ). The type specimen is unusual in having two inflorescences, one pistillate and one staminate.

Figures

FIGURE 3. Rhapis kebangensis. A. Plants growing in limestone rock. B. Leaf sheath and ligules. C. Abaxial surface of newly exposed leaf. D. Flowers and fruit.

FIGURE 4. Distribution maps of Rhapis kebangensis, R. laosensis, R. micrantha, and R. puhuongensis.