Ravenea rivularis Jum. & H.Perrier, Ann. Inst. Bot.-Géol. Colon. Marseille , III, 1: 54 (1913)

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Introduction

  • An aptly named species, since it only grows along riverbanks. It has recently become very popular in cultivation, and when well-watered grows at an impressive speed. The species can be admired from the main road Ihosy-Tulear, in a large stand at Ilkaka village near the Isalo National Park. (J. Dransfield & H. Beentje, The Palms of Madagascar. 1995)A

Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Madagascarpresent (World Checklist of Arecaceae)B
S central Madagascar, Mangoky and Onilahy river systems. (J. Dransfield & H. Beentje, The Palms of Madagascar. 1995)A

Discussion

  • The protologue mentions two populations, at Imaloto at the foot of the Isalo and at the Matitina R. near the sea (E Madagascar); the first one must have been the Perrier collection chosen as lectotype (which has staminate and pistillate flowers, as well as young fruit, just as in the protologue); the second one is only cited as Perrier s.n. in the Flore de Madagascar, a specimen which we have not seen; this might be an early collection of R. musicalis, the only eastern species looking vaguely like R. rivularis. HB has searched for palms at the site indicated, but failed to find a single (wild) one; older people did not know of any native palms, nor did they recognize the local name given (Akoraka in the Tanala language). Jumelle (1927b) mentions populations seen on Makay sandstone, in the Mangoky basin; the Flore de Madagascar adds the Sakeny R. valley (Menabe) and Madiovalo, just West of Ambato-Boeni, near the mouth of the Betsiboka R.; and the Bongolava (without mentioning which one; the name just means long plateau and there are several). The first three sites are indicated on the map by question marks. We consider the Madiovalo and Bongolava ones as unlikely; possibly these refer to riverside trees of R. sambiranensis, which has been collected in such a habitat on the (Miandrivazo) Bongolava. (J. Dransfield & H. Beentje, The Palms of Madagascar. 1995)A

Biology And Ecology

Conservation

Common Name

Description

  • Majestic tree palm. TRUNK 5-22 (30?) m, cylindrical or slightly inflated towards the middle, 36-50 cm diam., near crown 15-18 cm diam.; internodes 4-10 cm; wood with tough black fibre layer in the outer part; inner wood soft; bark pale brown-grey (not white, as Fl. Madagascar states!); diameter of base of crown c. 22 cm. LEAVES 16-25, porrect to pendulous, slightly arching, held on edge in the distal half of the leaf; sheath 30-50 x 15-16 cm, green and proximally with cottony white or grey-brown indument; margins ragged and fibrous; petiole 6-20 cm long, 4-4.5 x 1.5-1.6 cm across, adaxially flat with slightly sharp edges, white-waxy and -scaly; rachis green, white and scaly when young, 1.2-1.7 m long, 1-1.7 cm wide towards the middle, abaxially almost flat or slightly convex, densely pubescent to glabrescent, adaxially flat in the proximal half, more distally keeled with flat top and with the keel almost as wide as the rachis; leaflets regular, in one plane, stiff to pendulous, attenuate, green to slightly yellow, slightly waxy, 70-73 on each side of the rachis, the proximal 20-55 x 0.5-1.7 cm, the median 52-64 x 1.5-3.2 cm (interval c. 2 cm), the distal 16-42 x 0.4-1.9 cm, especially abaxially with the veins bearing minute whitish scales, also with a few large brown or grey ramenta on midrib abaxially. STAMINATE INFLORESCENCE multiple in 5s-7s (Fl. Mad. says solitary), erect, branched to 2 orders, 86-90 cm; peduncle 32-45 cm, green, proximally 0.9-1.1 cm across and densely pubescent, distally c. 0.8 cm across and glabrescent, slightly flattened; prophyll not known; peduncular bracts (based on one collection, cut just above base) 18 cm, 85 cm, 88 cm, 71 cm (the last inserted at 13 cm from the base of the peduncle), abaxially short-pubescent; non-tubular peduncular bract at 15-30 cm from the base, membranous, 35-41 x 2 cm; rachis bracts c. 6 x 0.2 cm at the base of the rachis; rachis 52- 89 cm, slightly pubescent; branches 60-100, dense; rachillae 3-21 cm long, sinuous in the distal part; bracteole c. 0.7 x 0.4 mm; pedicel 0.5-1 mm long. STAMINATE FLOWERS with the calyx connate for 0.5-0.7 mm, 0.6-1 mm across, free lobes 1.2-1.3 x 0.7-0.8 mm, triangular, acute; petals 3.5-5.8 mm, ovate, acute; filaments 0.4 (epipetalous, adnate for 0.3- 0.4 mm)-0.8 (free) mm; anthers 3.1-3.4 x 1.2-1.5 mm; pistillode 0.5 x 0.6 mm. FLOWERS with slight resinous smell. PISTILLATE INFLORESCENCES solitary, erect or spreading, branched to 1 order, 130-150 cm long; peduncle 40-60 cm, proximally 4 x 2.5 cm across, distally 1.2-2.2 x 1-1.8 cm across, green, white-scaly; prophyll 13-16 cm long, adnate for c. 2 cm; bracts narrow, 24-35 x 5-7 cm, 52-65 x 6 (inserted at c. 4 cm from the base of the peduncle), 110-130 x 5 (inserted at c. 5 cm), 124-150 x 4.5 cm (inserted at c. 6 cm), abaxially white-scaly; at c. 60 cm from the base with a non-tubular peduncular bract about 20 x 0.7 cm; proximal rachis bract 6-15 x 0.3 cm; rachis 50-72 cm, with 125-146 densely packed reflexed rachillae; rachillae 10-32 cm, 1.5 (-2.5 in fruit) mm across, with bulbous base, proximally 3.5 mm across, green with white bloom; pedicel 1-4 mm long. PISTILLATE FLOWER with the calyx connate for 1-1.3 mm, free lobes 1-1.3 x 1.3 mm, triangular, acute; petals ovate/triangular, acute, 3-3.5 x 2.5 mm; staminodes 6, short; ovary ovoid-conical, slightly shorter than the petals. FRUITS bright red, globose to slightly ellipsoid, 7.5-9 x 7-8.5 mm, 1-seeded, with bitter pulp; stigmatic remains subapical to lateral. SEED 5.5-6 x 5.5 mm. SEEDLING with 2 scale leaves and a bifid eophyll. (J. Dransfield & H. Beentje, The Palms of Madagascar. 1995)A

Materials Examined

  • Sakaraha: Manera, on the Fiherana[na] R., Oct. 1924 (fr.), Perrier 16580 (P). Ihosy: 40 km E of Ranohira, July 1992 (yfr.), H. Beentje & J. Beentje 4714 (BH, K, MO, P, TAN); idem, July 1992 (seedling), H. Beentje & J. Beentje 4715 (K); Ilkaka, Feb. 1992 (stam.), Beentje 4587 (BH, K, MO, P, TAN); upper Imaloto R., near Isalo, no date (stam., pist., yfr.), Perrier 11958 (Holotype P). (J. Dransfield & H. Beentje, The Palms of Madagascar. 1995)A