Rhapis evansii Henderson, 2016

Henderson, Andrew, 2016, A revision of Rhapis (Arecaceae), Phytotaxa 258 (2), pp. 137-152 : 141-142

1. Rhapis evansii Henderson sp. nov. Type:— LAOS. Vientiane: Vangvieng district, Ban Nathong, Tham Poukham, 18° 55’N, 102° 24’ E, 250–350 m, 1 August 1999, T. Evans 56 (holotype K!, barcode K000462531). ( Fig. 1 )

Rhapis evansii differs from all other species except R. puhuongensis and R. vidalii by its pedicellate flowers; it differs from both of these in its elliptic, multi-veined, acuminate central segments with the apices oblique and toothed.

Stems 0.8 m long, 0.5 cm diameter. Leaf sheath fibers coarse, flattened, forming a diagonal mesh, extended into a well-developed ligule; petioles 15.0 cm long, 1.1 mm wide at the apex; abaxial hastula usually complete, a low ridge separating petiole apex from costa; segments 6 per leaf; central segments elliptic, multi-veined, acuminate, the apices oblique, toothed, 23.0 cm long, 2.7 cm wide at midpoint, free almost to the base, the non-split part 0.2 cm; lateral segments 21.0 cm long, 1.0 cm wide at midpoint, the non-split basal part 0.3 cm; abaxial surface of segments without scales, not indumentose when first exposed. Inflorescences slender; prophyll and peduncular bract narrow, tubular, not or scarcely overlapping, the inflorescences exerted apically through the bracts on a curved peduncle; rachis length not recorded; rachillae slender, filiform, usually <1 mm wide; rachillae length not recorded; flowers pedicellate; flowers and fruits not recorded.

Distribution and habitat:—Central Laos in lowland forest on karst limestone outcrops at 250–350 m elevation ( Fig. 2 ).

Taxonomic notes:— Although complete inflorescences and flowers are not known, the species is immediately distinguished by the combination of elliptic segments and pedicellate flowers.

Figures

FIGURE 1. Type specimen of Rhapis evansii.

FIGURE 2. Distribution maps of Rhapis evansii, R. excelsa, R. gracilis, and R. humilis.