Howea Becc., Malesia 1: 41 (1877)

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Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Norfolk Is.present (World Checklist of Arecaceae)B
Two easily distinguished species endemic to Lord Howe Island. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Discussion

  • The two species of Howea are the largest palms in theLinospadicinae. Howea belmoreana is distinguished by curvedleaves with erect leaflets and by a single spike in each leaf axil,while H. forsteriana has rather flat leaves with drooping leafletsand several spikes in each leaf axil. Flowers and fruits matureslowly so that several inflorescences in different stages areoften present on a single tree.
    Recent research has demonstrated that Howea speciated sympatrically on Lord Howe Island and is thus a rare convincing example of this controversial mode of speciation (Savolainen et al. 2006).
    (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Diagnosis

  • Spectacular pinnate-leaved palms endemic to Lord Howe Island, where they occur in huge populations; distinctive in the robust pendulous spicate inflorescences and staminate flowers with large numbers of stamens. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Biology And Ecology

  • Howea forsteriana is abundant on the island in lowland forest on sandy areas; H. belmoreana can be found as scattered individuals with H. forsteriana, but becomes abundant at higher elevations up to about 450 m above sea level. Wind has been shown to be the primary pollinator, one of the few proven examples in the palms (Savolainen et al. 2006). (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Common Name

  • Kentia palms, Howea palms, sentry palms. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Etymology

  • Derived from Lord Howe Island, which in turn commemorates Admiral Lord Richard Howe (1726–1799). (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Uses

  • Both species, but especially Howea forsteriana, are important as commercially grown ornamentals. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Description

  • Moderate, solitary, unarmed, pleonanthic, monoecious palms. Stem erect, bare, conspicuously marked with close, horizontal or oblique leaf scars, the base sometimes expanded into a knob. Leaves pinnate, neatly abscising but not forming a crownshaft; sheath well developed, splitting longitudinally opposite the petiole, disintegrating into an interwoven mass of fine fibres; petiole short to moderately long, flattened or slightly channelled adaxially, abaxially ± angled, sparsely to densely scaly; rachis ± rounded to angled abaxially, adaxially angled, scaly as the petiole; leaflets numerous, single-fold, regularly arranged, curved or stiffly ascending, acute, acuminate or minutely bifid, adaxially with sparse scattered scales, abaxially ± glabrous or rather densely dotted with scales and bearing abundant floccose indumentum and ramenta along the midrib, transverse veinlets obscure. Inflorescences interfoliar, sometimes becoming infrafoliar after leaf fall, short or almost as long as the leaves, spicate, solitary or compound with up to 3–8 borne together on a common axillary boss, erect at first, later pendulous, protandrous; peduncle ± elliptic in cross-section, much shorter than or ± equalling the rachis, densely scaly; prophyll tubular, membranous; peduncular bract inserted near to or some distance from the prophyll, enclosing the inflorescence until anthesis, ± membranous, tubular, later splitting down its length, disintegrating and falling, leaving a low collar; rachis robust, scaly, densely covered with spirally arranged, ± spreading, low, rounded or triangular, rigid, coriaceous bracts, each forming a lip to a floral pit, enclosing a triad of flowers, except at the very tips where pits enclosing paired staminate flowers; floral bracteoles ± sepal-like. Staminate flowers partially exserted one at a time from the pit at anthesis; sepals 3, distinct, imbricate, usually keeled, ± rounded, the margins toothed; corolla with a stalk-like base ± as long as the sepals, and 3 ovate, valvate lobes; stamens 30–70 or more, filaments elongate, variously connate at the base for much of their length, the connective sometimes prolonged into a point, anthers elongate, ± latrorse; pistillode absent. Pollen ellipsoidal, asymmetric to pyriform; aperture a distal sulcus; ectexine tectate, finely perforate-rugulate, or granular-rugulate, especially on proximal face, aperture margin finely perforate-rugulate; infratectum columellate; longest axis 37–52 µm [2/2]. Pistillate flowers ± globular; sepals 3, distinct, imbricate, rounded, the margins toothed; petals 3, distinct, basally strongly imbricate, the tips briefly valvate; staminodes 3–6, forming a low, irregularly lobed, membranous ring, or irregularly separated as triangular or bifid flanges; gynoecium unilocular, uniovulate, tipped with 3 short stigmas ± reflexed at anthesis, ovule laterally attached, campylotropous. Fruit ovoid, sometimes faintly ridged, 1-seeded, shiny dark green at first, turning dull yellowish-green or reddish-brown, perianth whorls persistent, stigmatic remains apical; epicarp smooth, mesocarp rather thinly fleshy with abundant longitudinal fibres, endocarp cartilaginous, not adhering to the seed. Seed laterally attached, raphe extending 1/3 the length of the seed or less, endosperm homogeneous; embryo basal. Germination adjacent-ligular; eophyll bifid. Cytology: 2n = 32. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Anatomy

  • Leaf (Tomlinson 1961), root (Seubert 1998a,1998b), and fruit (Essig 2002). (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Fossil record

  • No generic records found. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Relationships

  • Howea is strongly supported as monophyletic(Savolainen et al. 2006, Baker et al. in prep.). For relationships,see Linospadix. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Taxonomic accounts

  • Bailey (1939a). (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)A

Bibliography

A. J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008
B. World Checklist of Arecaceae