Rhopaloblaste augusta (Kurz) H.E.Moore

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: threatened. Confidence: confident

Vernacular

Not known.

General Description

Robust, mid-storey, solitary palm bearing up to 11 leaves in the crown. Stem to 25 m tall, 20 - 30 cm diam., surface brown, becoming grey with age, leaf scars conspicuous. Leaf sheath 48 - 60 cm long, greyish brown, lepidote tomentose; crownshaft 50 - 61 cm long, 30 - 40 cm diam.; petiole short, 8 - 10 cm long, concave on adaxial and rounded abaxially; rachis 2 - 4 m long, with dense interlocking pale whitish brown scales on the abaxial surface especially when young, but becoming brownish black with age, less dense whitish brown scales on the adaxial surface; leaflets 90 - 100 each side of rachis, borne 3.5 - 4 cm apart, in one plane, pendulous, middle leaflet 60 - 70 x 2 - 3 cm, sublinear, acuminate, tapering acutely and bifid at the apex, discolorous, with sparse ramenta present along the mid-veins of the pinnae on the abaxial surface, and with rusty dark brown membranous scales on the adaxial surface, persisting at the base of the pinnae. Inflorescence 40 - 60 cm long, branched to 3 orders, primary branches 14 - 16, 45 - 56 cm long, basal pair of primary branches strongly recurved; prophyll 40 - 45 cm long, with sparse greyish brown scales; peduncle 4 - 5 cm long; rachillae moderately slender, 36 - 43 cm long, 2.9 - 3.8 mm diam., dull greenish brown. Staminate flower symmetric, 6 - 6.8 mm long, 4 -4.8 mm diam.; sepals 2.5 - 3 x 2.6 - 2.8 mm, strongly imbricate, rounded; petals 4 - 4.5 x 3 - 3.5 mm, broadly elliptic; stamens 3.2 - 3.5 mm long, filaments 2 - 2.1 mm long, connate at the base, anthers 3 - 3.2 mm long, 0.8 - 1 mm diam.; pistillode conical, 4.3 - 4.5 mm long, 1 - 1.1 mm diam. at the base. Pistillate flower 4 - 4.1 mm long, 3.8 - 4 mm diam., borne throughout the rachillae; sepals 3.5 - 3.8 x 3 - 3.5 mm, rounded, margin on the apex serrate; petals 3.6 - 4 x 2.8 - 3 mm, broadly elliptic; staminodes 4, lobes 0.8 -1 x 0.9 - 1 mm, acute at the apex; gynoecium 2.8 - 3.1 mm long, 1.2 - 1.5 mm diam., ovoid. Fruit 22 - 26 mm long, 10 - 14 mm diam., elongate ellipsoid, orange to red when ripe; cupule of persistent perianth 7 - 8 mm long. Seed 17 - 20 mm long, 9 - 11 mm diam., elongate-ellipsoid, brownish, with a conspicuous impression over the hilum; testa brown.

Conservation

Data deficient.

Distribution

Known only from the Nicobar Islands, being more common in the northern islands according to Kurz (1875). Now cultivated quite widely throughout South East Asia and elsewhere.

Biology

Lowland rain forest.

Banka, R., & Baker, W. (2004). A Monograph of the Genus Rhopaloblaste (Arecaceae). Kew Bulletin, 59(1), 47-60. doi:10.2307/4111073

Type

India, Nicobar Islands, Camorta [Kamorta], Feb. 1875, Kurz s.n. (holotype CAL; isotype K!).

Morphology General Habit

Robust, mid-storey, solitary palm bearing up to 11 leaves in the crown

Morphology Stem

Stem to 25 m tall, 20 - 30 cm diam., surface brown, becoming grey with age, leaf scars conspicuous

Morphology Leaves

Leaf sheath 48 - 60 cm long, greyish brown, lepidote tomentose; crownshaft 50 - 61 cm long, 30 - 40 cm diam.; petiole short, 8 - 10 cm long, concave on adaxial and rounded abaxially; rachis 2 - 4 m long, with dense interlocking pale whitish brown scales on the abaxial surface especially when young, but becoming brownish black with age, less dense whitish brown scales on the adaxial surface; leaflets 90 - 100 each side of rachis, borne 3.5 - 4 cm apart, in one plane, pendulous, middle leaflet 60 - 70 x 2 - 3 cm, sublinear, acuminate, tapering acutely and bifid at the apex, discolorous, with sparse ramenta present along the mid-veins of the pinnae on the abaxial surface, and with rusty dark brown membranous scales on the adaxial surface, persisting at the base of the pinnae

Morphology Reproductive morphology Inflorescences

Inflorescence 40 - 60 cm long, branched to 3 orders, primary branches 14 - 16, 45 - 56 cm long, basal pair of primary branches strongly recurved; prophyll 40 - 45 cm long, with sparse greyish brown scales; peduncle 4 - 5 cm long; rachillae moderately slender, 36 - 43 cm long, 2.9 - 3.8 mm diam., dull greenish brown

Morphology Reproductive morphology Flowers

Staminate flower symmetric, 6 - 6.8 mm long, 4 -4.8 mm diam.; sepals 2.5 - 3 x 2.6 - 2.8 mm, strongly imbricate, rounded; petals 4 - 4.5 x 3 - 3.5 mm, broadly elliptic; stamens 3.2 - 3.5 mm long, filaments 2 - 2.1 mm long, connate at the base, anthers 3 - 3.2 mm long, 0.8 - 1 mm diam.; pistillode conical, 4.3 - 4.5 mm long, 1 - 1.1 mm diam. at the base Pistillate flower 4 - 4.1 mm long, 3.8 - 4 mm diam., borne throughout the rachillae; sepals 3.5 - 3.8 x 3 - 3.5 mm, rounded, margin on the apex serrate; petals 3.6 - 4 x 2.8 - 3 mm, broadly elliptic; staminodes 4, lobes 0.8 -1 x 0.9 - 1 mm, acute at the apex; gynoecium 2.8 - 3.1 mm long, 1.2 - 1.5 mm diam., ovoid

Morphology Reproductive morphology Fruits

Fruit 22 - 26 mm long, 10 - 14 mm diam., elongate ellipsoid, orange to red when ripe; cupule of persistent perianth 7 - 8 mm long

Morphology Reproductive morphology Seeds

Seed 17 - 20 mm long, 9 - 11 mm diam., elongate-ellipsoid, brownish, with a conspicuous impression over the hilum; testa brown.

Distribution

Known only from the Nicobar Islands, being more common in the northern islands according to Kurz (1875). Now cultivated quite widely throughout South East Asia and elsewhere.

Ecology

Lowland rain forest

Conservation

Data deficient.

Note

R. augusta is distinct in its medium-sized, elongate, ellipsoid fruits, moderately slender fruit- bearing rachillae and inflorescences branched to three orders. It is a promising ornamental species, grown in botanical gardens for its bright fruits and attractive foliage.

Use

Of all the species of Rhopaloblaste, R. augusta is perhaps the most widely grown species for ornamental purposes.