Ravenea declivium

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Ravenea (rah-vehn-EH-ah)
declivium (deh-klih-VEE-uhm)
Rd687943200.JPG
Ravenea declivium, leaf rachis and emerging leaflets covered with wax and punctiform scales. Madagascar. Photo by Dr. Mijoro Rakotoarinivo/Kew.
Scientific Classification
Genus: Ravenea (rah-vehn-EH-ah)
Species:
declivium (deh-klih-VEE-uhm)
Synonyms
None set.
Native Continent
Africa
Africa.gif
Morphology
Habit: Solitary
Leaf type: Pinnate
Culture
Survivability index
Common names
None.

Habitat and Distribution

MADAGASCAR. Toliara, Taolagnaro, Iabokoho, Tsitongambarika, Ivohibe, about 4 km west of Antsotso
Madagascar. Photo by Dr. Mijoro Rakotoarinivo/Kew.
village, 24° 34’ 43” S, 47° 12’ 12.1” E, alt. 286 m, 24 September 2010, J. Dransfield & M. Rakotoarinivo with S. Dransfield, Ramisy Edmond, Mara Bergé JD7786 (holotype K, isotypes MO, TAN); JD7787 (K, TAN). This distinctive species occurs perched on the lips of rock faces and along seasonal watercourses in rather open, low crown forest on hill slopes at an elevation of about 250–350 m above sea level. Soils are shallow and have a well-developed humus layer overlying a thin sandy layer. (Dr's. RAKOTOARINIVO, M. AND J. DRANSFIELD. 2012)/Kew.

Description

Robust palm with decumbent short stem to 40 cm diam., generally appearing acaulescent. Stem clothed in persistent shaggy leaf base remains. Leaves ca. 17 in crown appearing to be quadrifarious or quinquefarious, strongly curved, marcescent, litter trapping, to 3 m long; petiole to 1.25 m long, to ca. 5 cm wide at the base, c.1.5 cm thick at the midline, decreasing to ca. 1.5 × 1.5 cm at the insertion of the basal leaflets, leaf sheath open, green, young leaf bases glaucous, abaxially with scattered brown elongate peltate scales, 2–6 × 0.8–1.1 mm, and a thin covering of amorphous gray indumentum, petiole deeply channeled throughout, the margins razor sharp; rachis to 1.75 m long, arcuate, tapering gradually throughout its length, deeply channeled proximally, ± triangular in cross-section distally, bearing abundant elongate dark brown peltate scales as the petiole; leaflets to 18 on each side of the rachis, broad, leathery, bluishgreen, cucullate and with long drip tips, basal leaflets 60–70 × 1.5–2 cm, mid-leaf leaflets 60–65 × 6–7 cm, apical leaflets 17–28 × 2–4 cm, drip tips terete to 75 × 2 mm, adaxial leaflet surface glabrous, smooth and slightly glossy when fresh, abaxial surface with scattered minute brown punctiform scales and with scattered dark brown peltate scales as the rachis along the margins exposed in bud. Staminate inflorescences multiple, up to 3 in the leaf axil, already dead, to 80 cm long, mostly hidden among the leaf bases; prophyll ca. 11 × 3 cm, incompletely sheathing, thin, papery, with a triangular 2-keeled tip, striate, abaxially with abundant caducous brown scales and hairs, adaxially glabrous; peduncular bracts 3, first 17–27 × 2 cm, second 30 × 1–1.5 cm, third 42 × 8 cm; peduncle 40–60 cm long, ca. 8 mm diam.; rachis 15–30 cm long, branched to 1 order only; rachillae numerous, 8–16 cm long, ca. 1.5 mm diam., with rather distant flower scars, up to 35 in all, surface glabrous. Flowers borne on short pegs to 1.5 × 0.3 mm; staminate flowers available only as minute scarcely differentiated buds. Pistillate inflorescence solitary at the node, branched to 1 order, 58–70 cm long; prophyll not seen; peduncle 40–48 cm long, ca. 5–6 mm diam., rounded in cross section; peduncular bracts 3, the first 27 × 2 cm, the second 32 × 1.5 cm, the third to at least 30 × 1.5 cm; rachis ca. 12 cm long; rachillae numerous 6–8 × 1–2 mm; flower scars ca. 50 per rachilla, flowers borne on short protuberances ca. 0.7 mm high. Pistillate flowers and fruit not seen. (Dr's. RAKOTOARINIVO, M. AND J. DRANSFIELD. 2012)/Kew. Editing by edric.

This astonishing palm represents perhaps our most exciting find on Ivohibe. It is an acaulescent (“stemless”) solitary palm restricted to rock outcrops, tending to grow on the lip of cliffs and on outcrops beside dry stream courses. It has a very short stem, decumbent at the base, ca. 35 cm diameter and covered with old leaf bases. There are about 8 leaves to 2 m long in the crown; petioles are glaucous, and the leaflets are few in number, distant, curved, very dark green and hooded, and unusually broad; they have an almost succulent texture. Male inflorescences are solitary or multiple in the leaf axils and females are solitary. We found material in old inflorescence and in bud. In all we estimate that we saw about 50 mature palms and rather few juveniles and seedlings. This is undoubtedly undescribed and a most unusual species in the genus. (Dr's. RAKOTOARINIVO, M. AND J. DRANSFIELD. 2012)/Kew.

Culture

Comments and Curiosities

Conservation status: IUCN - Critically Endangered; CR (B2ab(ii,iii,v);D). Known only from a single site in the summit area of Ivohibe forest where the area of occupancy is less than 1 km square and where only three mature individuals have been seen. The forest where this species has been recorded is not officially protected and may be subjected to human pressure that could affect the quality of the habitat and probably the loss of mature individuals. (Dr's. RAKOTOARINIVO, M. AND J. DRANSFIELD. 2012)/Kew.



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).

Dr's. RAKOTOARINIVO, M. AND J. DRANSFIELD. 2012


Many Special Thanks to Ed Vaile for his long hours of tireless editing and numerous contributions.

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