Dypsis rivularis
Dypsis (DIP-sis) rivularis (rih-voo-LAH-riss) | |||||||
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SE Queensland, Australia. Photo by Benjamin Smith | |||||||
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Contents
Habitat and Distribution
Endemic to Madagascar. Mananjeba River, Manongarivo, Ankarafantsika. Moist forest stream edge, among boulders; alt. 130-300 m.Description
Solitary palm, with untidy crown and stilt roots. TRUNK 4-5.5 m, high, 4.5-15 cm. in diam., internodes 3.5-6 cm long, near the crown about 2 cm. LEAVES spirally inserted, arching, 7-14 in the crown; sheath 3/4 open, 26-43 cm, yellow with few scattered reddish scales and erose ligules about 1 cm long; petiole absent or up to 2 cm; rachis about 1.4 m long, proximally 1.5-2 cm wide, in mid-leaf 0.8-1.3 cm wide, reddish with dense pale flaking indument, glabrescent; pinnae about 32 on each side of the rachis, in groups of 2-5 in the proximal and middle part of the leaf to almost over the entire length of the leaf, the groups 8-19 cm apart, but often with the pinnae in the distal half or third regular; proximal pinnae 12-64 x 0.3-3.7 cm, median 42-68 x 3.3-6 cm (interval within groups 1.5-3.5 cm), distal 13-36 x 0.6-2.8 cm, main veins 5-7, veins with many minute reddish scales abaxially and sometimes adaxially, few or no ramenta, apex (unequally) attenuate. INFLORESCENCE interfoliar at anthesis to infrafoliar in fruit, about 90 cm, branching to 3 orders; peduncle 43-46 cm, densely puberulous, proximally about 8 x 3 mm, distally about 7 x 4 mm in diam.; prophyll 39-56 cm, borne at 8-14 cm above the base of the peduncle, 1.6-4.5 cm wide, with rather dense reddish scales and sometimes with a waxy bloom; peduncular bract inserted at about 26 cm, 20-32 cm long, beaked for about 1 cm, with scattered scales, deciduous; rachis 30-50 cm, densely reddish puberulous, with 17-20 branched and 3-7 unbranched first order branches; proximal first order branches to 50 cm long, with 7-10 branched and 10 unbranched second order branches, proximally to 1.5 x 0.7 cm. in diam.; rachillae 3-19 cm, densely puberulous, about 1 mm. in diam.; triads distant, superficial, with entire rounded bract. STAMINATE FLOWERS unknown at anthesis, but in young bud with sepals 0.7-1 x 1-1.3 mm, ciliolate; petals 1.2-1.6 x 1.2-1.4 mm; stamens 6, biseriate, with filaments 0.4-0.5 mm long, cylindrical, with didymous anthers 0.5-0.6 x 0.5 mm; pistillode < 0.5 mm. PISTILLATE FLOWERS yellow, without discernible scent, with sepals 0.8-1.1 x 1.4-1.8 mm, broadly elliptic, rounded, minutely ciliate; petals 1.8-2.6 mm long, with the lower part membranous, concave, 1-1.4 x 1.3-2 mm, the upper part fleshy, triangular, flat, 0.8-1.2 x 1.2-1.4 mm; staminodes 6, 0.2-0.3 mm; ovary 1.5-1.8 mm high, asymmetrical, 1.8-2.2 mm. in diam., with very divergent stigmas 0.5-0.6 mm long. FRUIT ellipsoid, slightly curved, 12-14 x 5-7 mm, asymmetrical; base and apex rounded; endocarp fibrous, the fibres hardly anastomosing. SEED 10-11 x 4.5-5 mm, rounded at base, slightly pointed at apex, with homogeneous endosperm. (J. Dransfield and H. Beentje. 1995)/Palmweb. Editing by edric.
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There are some differences between the type (which is from the Ankarafantsika) and the Manongarivo populations. These consist of the width of the leaflets (much wider in the type: 6 cm as opposed to 3-4 cm) and the length of the rachillae (shorter in the type: 3-7 cm as opposed to 8.5-19 cm). However, we feel these differences can be attributed to variation between populations, and we do not believe they warrant taxonomic distinction, since the similarities between the type and the other population are large. Jumelle describes the palm as 5-10 m tall. This information does not appear on any of the Perrier specimen labels, and we have not included it in the description. There are recent but unsubstantiated reports of a population of large palms growing along a river in the Ankarafantsika, which might confirm Jumelle's data. He also describes the male flowers as having sepals 1.35 x 1.5 mm; petals 2 x 2 mm; anthers with short, wide filaments and a connective projecting beyond the locules, which are said to be divergent at the base. We have only been able to find young staminate buds on Perrier 15803; these differ from Jumelle's description. (J. Dransfield and H. Beentje. 1995)/Palmweb. |
Culture
Dypsis rivularis grows readily in a moist and lightly shaded position. It is a water lover and potted plants thrive if left sitting in 1 to 2 cm of water. Cold Hardiness Zone: 10a
Comments and Curiosities
A charming palm, but with a rather untidy look to it, due to the irregular grouping of the leaflets. The name indicates its habit of growing along rivers. This species may be in cultivation in Queensland, where JD has seen juveniles of a palm that seem to match the herbarium specimens from the wild.(J. Dransfield and H. Beentje. 1995)/Palmweb.
Conservation: Vulnerable. Only known from two recent sites; total population estimated at less than a hundred. (J. Dransfield and H. Beentje. 1995)/Palmweb.
External Links
References
Phonetic spelling of Latin names by edric.
Special thanks to Geoff Stein, (Palmbob) for his hundreds of photos.
Special thanks to Palmweb.org, Dr. John Dransfield, Dr. Bill Baker & team, for their volumes of information and photos.
Glossary of Palm Terms; Based on the glossary in Dransfield, J., N.W. Uhl, C.B. Asmussen-Lange, W.J. Baker, M.M. Harley & C.E. Lewis. 2008. Genera Palmarum - Evolution and Classification of the Palms. Royal Botanic Gardens, Kew. All images copyright of the artists and photographers (see images for credits).
Dransfield, J. & Beentje, H. 1995. The Palms of Madagascar. Royal Botanic Gardens, Kew and The International Palm Society.
Many Special Thanks to Ed Vaile for his long hours of tireless editing and numerous contributions.