Hydriastele aprica (B.E. Young) Baker & Loo (2004: 62)

Petoe, Peter, Heatubun, Charlie D. & Baker, William J., 2018, A monograph of Hydriastele (Areceae, Arecaceae) in New Guinea and Australia, Phytotaxa 370 (1), pp. 448-450 : 448-450

12. Hydriastele aprica (B.E. Young) Baker & Loo (2004: 62) . Gronophyllum apricum Young (1985: 139) . Type:— PAPUA NEW GUINEA. Sandaun Province: Telefomin Subprovince, rainforest below Carpentaria Exploration Co. helipad K-27 on exposed ridge, 900 m, 4°45’S, 141°50’E, 1 May 1978, Essig & Young LAE 74082 (holotype LAE!, isotype BH)

Figure 26 (line drawing). Figure 23 (map).

Solitary, slender palm to 5 m tall, bearing ca. 7 leaves in crown. Stem ca. 3 cm in diam. Leaf 48–80 cm long including petiole; sheath 21–23 cm long; petiole 12–18 cm long; leaflets 15–23 per side, irregularly arranged, drooping, cuneate, concavely praemorse apically, with ramenta present on the abaxial side of the midrib. Inflorescence 15–26 cm long including 3.2–5.5 cm peduncle, branched to 1 order, protandrous; rachillae 4–6; triads opposite and decussate. Staminate flower 3–7 × 0.5–3 mm in bud (when dry), cream with purplish tips; stamens 6. Pistillate flower 1.5–7 × 1–2 mm in bud (when dry), dark purple, with free sepals and petals with long and thin, valvate tips. Fruit ca. 8 × 7 mm, subglobose, red, apical stigmatic remains not seen. Seed ca. 5 × 4 mm; endosperm homogeneous.

Distribution:— Northern central New Guinea.

Habitat:— Montane forest on sun-exposed limestone ridges, 300–1200 m.

Uses:— None recorded.

Vernacular names:— None recorded.

Conservation status:— Data deficient (DD; Heatubun et al. 2018).

Specimens examined:— PAPUA NEW GUINEA. Sandaun Province: Telefomin Subprovince, on ridge above junction of “clear-water” stream with Frieda R., ca. 2 km upstream from Carpentaria Exploration Company airstrip camp, 300 m, 26 April 1978, Essig & Young LAE 74049 (BH, LAE!, USF); Telefomin Subprovince , rainforest below Carpentaria Exploration Co. helipad K-27 on exposed ridge, 900 m, 4°45’S, 141°50’E, 1 May 1978, Essig & Young LAE 74082 (BH, LAE!); on exposed ridge near Carpentaria Exploration Co. “Antap Mt” helipad, 1200 m, 4°45’S, 141°50’E, 29 April 1978, Essig & Young LAE 74072 (BH, LAE!, USF) .

Notes:— Hydriastele aprica is a highly distinctive, slender palm immediately recognisable on account of its drooping leaflets with concavely praemorse tips. The species is further distinguished by being the only member of the Nengella group with decussately arranged triads. We note that the habitat preference of this species is also unusual within the genus. More details are given by Young (1985) and Heatubun et al. (2018).

MICROCARPA GROUP

Moderately slender palms, inflorescences protandrous and branched to 2 orders, triads spirally arranged. The Moluccas and New Guinea.

Figures

FIGURE 23. Distribution map of part of the species of the Nengella group of Hydriastele.

FIGURE 26. Hydriastele aprica. A. Leaf diagram. B. Leaf apex. C. Mid-leaf portion. D. Inflorescence with pistillate flowers.E. Staminate flower whole and in longitudinal section. F. Pistillate flower. G. Fruit whole and in longitudinal section. Scale bar:A = 18 cm; B–C = 4 cm; D = 3 cm; E–G = 4 mm.A, F–G from Essig & Young LAE 74049; B–E from Essig & Young LAE 74072. Drawn by Lucy T. Smith.