Calamus jacobsii W.J.Baker & J.Dransf., 2017

Baker, William J. & Dransfield, John, 2017, More new rattans from New Guinea and the Solomon Islands (Calamus, Arecaceae), Phytotaxa 305 (2), pp. 61-86 : 70-72

5. Calamus jacobsii W.J.Baker & J.Dransf. , sp. nov. Type:— PAPUA NEW GUINEA. Morobe: south-east of Lae on the coast, opposite Lasanga Island, 500–600 m, 7°25’S, 147°10’E, 11 November 1973, Jacobs 9561 (holotype L!, isotypes LAE).

Diagnosis:— Distinguished by the leaves and leaf sheaths drying brown, the unarmed leaf sheath, the very short petiole, the few, subregularly arranged, elliptic leaflets, and the non-flagelliform staminate inflorescence that is branched to 4 orders.

Moderately robust rattan climbing to 15 m. Stem with sheaths 18–24 mm diam., stem without sheaths not seen; internodes ca. 35 cm. Leaf ecirrate to 76 cm long including petiole; sheath brown when dried, with thin, dense, caducous indumentum consisting of minute, cup-shaped, translucent, colourless scales and brown or colourless fibrous scales, spines lacking; knee 25 mm long, colour and indumentum as sheath; ocrea 4–6 mm high, forming an inconspicuous bony crest that extends into the lower part of the petiole, unarmed, colour and indumentum as sheath, persistent; flagellum to ca. 220 cm; petiole ca. 5 mm long, ca. 7.5 mm wide and ca. 5 mm thick at base, shallowly grooved adaxially, rounded abaxially, indumentum as sheath, armed with one or two solitary grapnel spines abaxially; rachis ca. 40 cm, armed with scattered solitary or grouped grapnel spines abaxially; leaflets ca. 4–5 each side of rachis, subregularly arranged, broadly elliptic, longest leaflet at mid-leaf position, mid-leaf leaflets ca. 37 × 8 cm, apical leaflets 35 × 5 cm, apical leaflet pair united to approximately two thirds of their length, leaflets unarmed except for very rare minute marginal bristles at apex, with scattered patches of indumentum as leaf sheath, transverse veinlets conspicuous; Staminate inflorescence arching, moderately robust, at least 87 cm long (complete inflorescence not seen), apparently lacking flagelliform tip, branched to 4 orders; prophyll not seen; peduncular bracts at least 1, peduncular and rachis bracts 7–26 × 0.7–1.2 cm, strictly tubular with asymmetrically pointed tip, not splitting, with indumentum as sheath, unarmed; primary branches at least 3, to ca. 21 cm long, 16–26 cm apart, erect, diffusely and finely branched, with numerous rachillae, bracts to 18 × 4 mm, funnel-shaped, relatively conspicuous, with indumentum as sheath; rachillae 5–16 mm × 0.5–1 mm, straight to slightly recurving; rachilla bracts ca. 1.5 × 0.5–1 mm, distichous, explanate, apiculate, with scattered indumentum as sheath; floral bracteole 1.3–1.5 × 0.8–1 mm, flattened, glabrous. Staminate flowers ca. 2 × 1.3–1.8 mm in early bud, immature. Pistillate inflorescence not seen. Pistillate flowers not seen. Sterile staminate flowers not seen. Fruit not seen. Seed not seen.

Etymology:— The species is named for Marius Jacobs (1929–1983), a senior botanist of the Rijksherbarium, Leiden and collector of the type specimen. Jacobs died at the age of 53, unexpectedly cutting short his career in plant taxonomy and conservation in Malesia ( Kalkman 1983).

Distribution:— Known from two localities in mountains south of Lae, Papua New Guinea.

Habitat:— Primary forest at an elevation of 500– 600 m.

Uses:— None recorded.

Vernacular names:— None recorded.

Specimens examined:— PAPUA NEW GUINEA. Morobe Province: south-east of Lae on the coast, opposite Lasanga Island , 500–600 m, 7°25’S, 147°10’E, 11 November 1973, Jacobs 9561 (holotype L!, isotypes LAE) ; ridge crest in mountains north-west of Ana village , 7°48’S, 147°33’E, 500 m, Essig LAE 55159 ( LAE!, BH) .

Notes:— Calamus jacobsii is known from relatively incomplete material from two collections, one including a staminate inflorescence in bud (the type, Jacobs 9561), the other (Essig LAE 55159) an apparently juvenile sterile specimen. Nevertheless, it is sufficiently distinct to be described as new here. The species dries a distinctive brown colour. The leaf sheath is unarmed and covered with thin, but dense, caducous indumentum, which also occurs on other organs. The petiole is very short (ca. 5 mm) and the leaf bears very few (4–5), large, elliptic leaflets, which are themselves almost entirely unarmed. The staminate inflorescence seen by us is not flagelliform and is branched to four orders. It is perhaps most easily confused with C. johnsii , a robust form of which also occurs in the vicinity of the type locality of C. jacobsii (Jacobs 9698, L!). The two species are similar in leaflet size, shape and number and the lack of a petiole. Calamus johnsii , however, is more slender, dries pale green, is armed on its leaf sheath with planar, black spines, and bears slender, whip-like inflorescences that have a flagelliform tip and that are branched to three orders in the staminate. Calamus johnsii is also not known from above 350 m elevation.