Ravenea H.Wendl. ex C.D.Bouché, Monatsschr. Vereines Beförd. Gartenbaues Königl. Preuss. Staaten 21: 324 (1878)

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Number of Taxa

  • 21 species

Discussion

Biology And Ecology

  • Occurring in tropical rain forest from sea level to 2000 m, including mossy montane forest, one species (Ravenea xerophila) in spiny forest in the driest area of Madagascar, another (R. musicalis) growing in flowing water and starting its life as a submerged aquatic. Often gregarious, the rain-forest species sometimes grow in full light. (J. Dransfield, N. Uhl, C. Asmussen, W.J. Baker, M. Harley and C. Lewis. 2008)

Common Name

Etymology

Diagnosis

Description

  • Solitary, slender to robust, unarmed, dioecious, pleonanthic palms. Stem erect, rarely very short, very rarely branching dichotomously, often tall, becoming bare, sometimes swollen at the base, conspicuously ringed with leaf scars or not. Leaves few to numerous, reduplicately pinnate, often upward pointing, abscising neatly or marcescent, crownshaft absent; sheaths soon disintegrating opposite the petiole into fine or coarse fibres, densely tomentose; petiole very short to moderately long, adaxially flattened or channelled, abaxially rounded, usually densely tomentose; rachis flattened adaxially, triangular abaxially, sometimes channelled laterally; leaflets numerous, single-fold, usually stiff, elongate, acute or acuminate, the proximal few sometimes very short and slender, abaxially frequently with small narrowly elliptic ramenta, rarely densely covered with white indumentum abaxially, midribs more prominent adaxially, transverse veinlets evident or not. Inflorescences interfoliar, 1 or several within a single prophyll in a leaf axil, usually large, sometimes highly condensed and hidden among the sheaths, the staminate and pistillate superficially similar but the staminate more slender, branched to 1–2 orders; peduncle slender to robust, very short to elongate, ± circular in cross-section distally, usually scaly or tomentose; prophyll short, 2-keeled, incomplete; peduncular bracts tubular, 3–5, 2 usually short, apically open and tattered, the 2 or more distal bracts narrow lanceolate, as long as and enclosing the inflorescence in bud, splitting longitudinally, all bracts persistent, always densely scaly or tomentose abaxially, membranous, coriaceous, or almost woody; rachis usually shorter than the peduncle, bearing spirally arranged, usually numerous, first-order branches, the first-order bracts very small, acute or long acuminate, usually adnate to the subtended branch; proximal first-order branches, subdigitately branched or unbranched, the distal unbranched; rachillae very short to elongate, usually stiff, slender, sometimes eventually pendulous, the staminate shorter and more slender than the pistillate, slightly zigzag, sparsely to densely scaly, bearing spirally arranged, rather lax peg-like floral stalks, each subtended by a minute, narrow triangular rachilla bract, usually adnate to the stalk. Flowers more crowded and somewhat grouped distally, congenitally open. Staminate flowers ± symmetrical; sepals 3, triangular, connate in the basal 1/3, adnate to the floral stalk, to the base of the stamen filaments and to the petal bases; petals 3, broadly ovate, distinct or rarely connate basally, fleshy; stamens 6, sometimes inserted in 2 series, filaments slender, short, basally expanded, shortly adnate to sepals and petals, rarely connate in an androecial ring; anthers straight or somewhat twisted, ± sagittate, latrorse. Pollen spheroidal, aperture a distal pore; ectexine tectate, scabrate-perforate with supratectal spines or, rarely, semi-tectate, foveolate-reticulate, pore margin similar to main tectum, or a slightly raised psilate annulus; longest axis 24–35 µm [9/17]. Pistillate flowers with sepals and petals similar to staminate; staminodes 6, broadly triangular with sterile anthers; gynoecium ovoid, tricarpellate, carpels connate, trilocular, triovulate, stigmas 3, fleshy, recurved, ovules pendulous, hemianatropous. Fruit 1–3 seeded globose to ellipsoid when 1-seeded, slightly lobed when more than 1 seed develops, yellow, orange or red, more rarely brown, purple or black, stigmatic remains subbasal, lateral, or subapical; epicarp smooth or minutely pebbled, mesocarp fleshy, endocarp thin. Seeds, globose, hemispherical or representing a third of a sphere, hilum basal, raphe branches indistinct, endosperm homogeneous; embryo basal. Germination adjacent-ligular or remote-ligular; eophyll bifid or pinnate. Cytology: 2n = 30, 32. (J. Dransfield, N. Uhl, C. Asmussen, W.J. Baker, M. Harley and C. Lewis. 2008)

Anatomy

Relationships

  • Ravenea is monophyletic with high support (Trénel et al. 2007). Two possible placements of Ravenea have been resolved: first, as sister to Oraniopsis with moderate support (Asmussen et al. 2006, Baker et al. in review) and, second, as sister to a clade of Oraniopsis, Ceroxylon and Juania (Uhl et al. 1995, Trénel et al. 2007). (J. Dransfield, N. Uhl, C. Asmussen, W.J. Baker, M. Harley and C. Lewis. 2008)

Taxonomic accounts

Uses

  • The trunk of Ravenea madagascariensis is very hard and flexible and is used in various ways; that of R. robustior has abundant pith, is rich in starch, and is used as a source of sago. The ‘cabbage’ of most species is edible but may be bitter. Trunks of R. musicalis are sometimes hollowed out to make canoes. Many species are widely traded as ornamentals, the most significant being R. rivularis (Majesty palm). (J. Dransfield, N. Uhl, C. Asmussen, W.J. Baker, M. Harley and C. Lewis. 2008)

Bibliography

  • Dransfield, J. , Uhl, N. , Asmussen, C. , Baker, W.J. , Harley, M. & Lewis, C. 2008. Genera Palmarum. The evolution and classification of palms. Kew Publishing, Royal Botanic Gardens Kew.