Pinanga rupestris J.Dransf., Kew Bull. 46: 693 (1991)

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Content

Distribution

Map uses TDWG level 3 distributions (https://github.com/tdwg/wgsrpd)
Borneo present (World Checklist of Arecaceae)B
This remarkable little 'pinang' is found only on the great sandstone cliffs and boulders of Bako National Park. (Dransfield, J. 1991: Notes on Pinanga (Palmae) in Sarawak)A

Discussion

  • P. rupestris, although superficially very different, seems to me to be related to the rheophyte, P. rivularis Becc., from neighbouring Brunei and the 4th and 5th Divisions of Sarawak. Both species are diminutive, and have internodal branching and simple, hairy inflorescence axes bearing gamosepalous pistillate flowers; the leaves of P. rivularis are, however, very finely pinnate as befits a rheophyte. (Dransfield, J. 1991: Notes on Pinanga (Palmae) in Sarawak)A

Diagnosis

  • habitatione egregia verosimiliter affinis P. rivulari Becc. inflorescentia spiciformi sepalis floris pistillati connatis et ramificatione internodiali sed lamina angusta integra breve bifida statim distinguibilis. (Dransfield, J. 1991: Notes on Pinanga (Palmae) in Sarawak)A

Biology And Ecology

  • It is by no means abundant, but is very distinctive. No fruits have been found although dead inflorescences can be seen on herbarium specimens and in the field. How the palm is dispersed to crevices in vertical cliffs is a mystery. (Dransfield, J. 1991: Notes on Pinanga (Palmae) in Sarawak)A

Description

  • Diminutive clustering palmlet, erect or more usually pendulous from crevices in sandstone rock faces. Stems rarely exceeding 60 cm long, usually much less, c. 4-6 mm diam., conspicuously marked with nodal scars, inter- nodes 1-3 cm, surface with scattered brown scales, stem base producing aerial roots and dense clusters of sucker shoots, the stem also frequently producing bulbil-like shoots from the middle of the distal internodes. Crown of about 6 leaves, the sheaths forming an elongate crownshaft; leaf sheaths c. 80 x 7 mm, striate on drying, covered in scattered dull brown scales, distally with a rapidly disintegrating laciniate ocrea to 16 mm; petiole of leaves of mature stems c. 8-17 cm, c. 3 mm diam., ± triangular in cross section, bearing scattered scales when fresh; blade dull brown or greenish brown when dry, narrow, entire, bifid, to 50 cm long, gradually widening from the base to 6 cm near the tip, usually shorter and narrower, split to 7.5 cm, the two halves with c. 6 shallow lobes to 7 mm deep; adaxial surface minutely punctate, abaxial surface bearing inconspicuous thin grey indumentum. Inflorescence unbranched, pendulous, 6 cm long; prophyll c. 6 x 1.4 cm; peduncle very short, not exceeding c. 7 mm; rachilla surface hairy; triads strictly distichous, borne in a plane radial to the stem, each subtended by a low rachilla bract to 1 mm high. Staminate flowers ± triangular ovate in outline, laterally flattened or curved by close packing; calyx irregularly 3-lobed, the lobes 1-2 mm high; petals cream-coloured, fleshy, irregular, two c. 6.5 x 3 mm, the third c. 6.5 x 4.5 mm; stamens 7-8, filaments c. 1 x 0.2 mm, anthers c. 2 x 0.6 mm, with broad connectives. Pollen grains monosulcate, ellipsoid in apertural view; long axis (31-)33.3(-36) µ/m, short axis (24 -)26.2(-30) µ/m, wall thickness c. 2 ,im; sulcus membrane not observed, sulcus somewhat longer than long axis; exine intectate, clavate, the larger clavae interspersed with smaller diameter, shorter clavae, clavae not modified at sulcus margin. Pistillate flower very low; calyx tubular, ± striate, c. 0.8 mm high, very shallowly 3-lobed; petals imbricate, ovate, c. 0.8 mm long, the margins sparsely ciliate; staminodes lacking; ovary c. 0.8 mm diam., tipped with an irregularly lobed stigma. Fruit not known. (Dransfield, J. 1991: Notes on Pinanga (Palmae) in Sarawak)A

Materials Examined

  • BORNEO. Sarawak: 1st Division, Bako National Park, Dransfield et al. JD5917 (holotype K; isotypes BH, L, SAR), Dransfield JD746 (K), Ashton S.17961 (K, SAR), Jugah ak Kudi S.36627 (BH, K, KEP, L, SAN, SAR). (Dransfield, J. 1991: Notes on Pinanga (Palmae) in Sarawak)A

Bibliography

    A. Dransfield, J. 1991: Notes on Pinanga (Palmae) in Sarawak
    B. World Checklist of Arecaceae