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Borassus aethiopum

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Miami FL. Photo by Ryan D. Gallivan, edric.
Borassus (bor-RAHS-sohs) aethiopum
(eh-thee-OH-puhm)
Borae0001z.jpg
Scientific Classification
Genus: Borassus (bor-RAHS-sohs)
Species: aethiopum
(eh-thee-OH-puhm)
Synonyms
None set.
Native Continent
Africa
Africa.gif
Morphology
Habit: Solitary
Leaf type: Palmately compound
Culture
Sun exposure: Full Sun
Survivability index
Common names
Dimaka (Sakalava, Madagascar), Kuhe (Ashanti, Ghana), Muhama (Kibuyu, Congo-Kinshasa), Mvumo (Kiswahili, Kenya & Tanzania). A list of West African vernacular names for B. aethiopum is provided by Burkill (1997). European names include African fan-palm, borassus-palm, rhun-palm, rônier (French) and palma-do-vinha (Portuguese). (R.P. Bayton. 2007). African fan palm, African palmyra palm, deleb palm, ron palm, toddy palm, black rhun palm, ronier palm (from the French).

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Contents

Habitat and Distribution

Benin, Burkina, Cameroon, Central African Republic, Chad, Comoros, Ethiopia, Ghana, Ivory Coast, Kenya, Madagascar, Malawi, Mali, Mozambique, Niger, Nigeria, Northern Provinces, Senegal, Sudan, Tanzania, Togo, Uganda, Zaire, Zambia, and Zimbabwe. Found across sub-Saharan Africa as far south as northern South Africa. Absent from parts of southwest and central Africa, and the Horn of Africa. Present on a number of offshore islands including São Tomé and Bioko in the Gulf of Guinea, three of the Cape Verde Islands, and Pemba, Zanzibar and Mayotte in the Mozambique Channel. Present in the Sambirano region of northwest Madagascar, including the islands of Nosy Bé and Nosy Mitsiou, though it may be introduced there. (R.P. Bayton. 2007/Palmweb.

Riverine forest and savanna in low-lying areas, particularly on sandy or alluvial soils. Borassus aethiopum can form dense almost monospecific forest stands or is a component of more diverse riverine forest. However, it is as the main component of palm savannas for which it is best known. Borassus aethiopum is well adapted to fire and herbivory and prospers in areas with frequent burning and browsing. After the pyrenes are dispersed, the embryo is buried underground by the extending cotyledonary petiole (Barot & Gignoux 1999). The meristem is thus protected in the early years of life during a period known as the establishment phase. After several years surviving as a small cluster of leaves, the palm finally generates a stem and this grows rapidly. At this stage, the meristem is vulnerable to fire and herbivory, but is protected to some extent by the skirt of dead leaves that clothes the stem. The dead leaf blades are highly-flammable, but the woody petioles are more persistent and this may allow brush fires to pass quickly; the leaf blade is quickly consumed, but the petiole burns slowly, keeping the fire away from the meristem. As a result, the stem is covered with petioles, which may also serve as a deterrent to large herbivores as the petioles are armed with spines. The accumulated leaf sheathes and petioles are shed cleanly at maturity (Barot & Gignoux 1999). At this point, the meristem is protected from fire and herbivory by virtue of its height above the ground. (R.P. Bayton. 2007)/Palmweb.

Description

They grow swelling, solitary trunks to 25 metres (82 ft.) high, and 1 metre (3 ft. 3 in.) in diameter at the base. The green leaves — 3 to 4 metres (10-12 ft.) wide — are carried on petioles — 2 metres (6 ft. 7 in.) long — which are armed with spines. The crownshaft is spherical to 7 metres (23 ft.) wide, the leaves are round with stiff leaflets, segmented a third or half-way to the petiole. In male plants the flower is small and inconspicuous; females grow larger, 2 centimetres (0.79 in.) flowers which produce yellow to brown fruit resembling the coconut containing up to 3 seeds.

Stem to 25m tall, almost always ventricose, to 80 cm in diameter. Leaves 18 – 27 in the crown; petiole and sheath 130 – 220 cm long; petiole 3.2 – 9 cm wide, robust, with large (0.4 – 2.8 cm long), recurved black teeth on the margins, yellow-orange in the distal portion, darkening to brown-black towards the trunk, though in immature plants, the petiole may be completely black; petiole spines extending along the margin of the first leaflet; costa 80 – 170 cm long; adaxial hastula conspicuous, to 2.9 cm high, abaxial hastula rudimentary; lamina radius to 190 cm maximum, dense indumentum on the ribs of some immature leaves; leaflets 86 – 120, 4.7 – 11 cm wide, apices acute and entire or splitting longitudinally with age, shortest leaflet 45 – 92 cm long, leaf divided to 58 – 95 cm; commissural veins 8 – 15 per cm, leaf anatomy isolateral. Staminate inflorescences branched to two orders, upper subtending branches terminating in 1 – 3 rachillae; rachillae green-brown and catkin-like, 37 – 50 cm long, 2.3 – 3.8 cm diameter, sometimes with a mamilliform apex; rachilla bracts form pits that contain a cincinnus of 8 – 14 staminate flowers. Pistillate inflorescences spicate; flower-bearing portion 36 – 160 cm long with 10 – 28 flowers arranged spirally. Staminate flowers 0.2 – 0.7 cm long, exserted individually from the pits; bracteoles 0.8 × 0.5 cm; calyx 0.4 × 0.2 cm and shallowly divided into three sepals, petal lobes 0.15 × 0.1 cm; stamens 6 with very short filaments, 0.02 × 0.04 cm, anthers 0.02 × 0.05 cm; pistillode minute. Pollen monosulcate, elliptical, 49 – 71 μm long, aperture 37 – 71 μm long, polar axis 32 – 61 μm long; tectum perforate, sparsely covered with supratectal gemmae. Pistillate flowers 3 × 3 cm, bracteoles 2 cm diam., sepals 1.5 × 2 cm and petals 1 × 1.5 cm. Fruits massive, 7 – 17 × 7 – 11 cm, ovoid, flattened at the apex, or with a depressed apex; fragrant, yellow to orange or red at maturity; produced inside persistent perianth segments; pyrenes 1 – 3, 6.4 – 10.9 cm × 5.4 – 8.0 cm × 4.2 – 5.7 cm, somewhat bilobed; some pyrenes have one or two external longitudinal furrows; internal flanges absent. (R.P. Bayton. 2007)/Palmweb. Editing by edric.

Historically, the key question in Borassus taxonomy has been whether to recognise both the African B. aethiopum and the Asian B. flabellifer. Most recent accounts do recognise B. aethiopum (Beccari 1924; Dransfield 1986a; 1988; Tuley 1995). The molecular study of Kovoor & Hussein (1983) also noted differences between the two species, though the population sampling was extremely limited. Qualitative characters that separate the two include the stem (ventricose in B. aethiopum and not in B. flabellifer), petiole spines (large in B. aethiopum, small in B. flabellifer), and fruit colour (black for B. flabellifer and yellow-orange for B. aethiopum). Beccari (1924) separated the African and Asian Borassus species based on the degree of division of the calyx lobes of the staminate flowers. The calyx of Asian species was divided to the base, while the calyx of African species was only divided to the middle. This character appears to be nothing more than an artefact of preparation. The calyx of most staminate flowers (of either Asian or African species) is divided to the middle. However, the transparent, membranous partitions between the calyx lobes tear easily. The resultant tear is perfectly straight, giving the impression that the calyx is divided to the base. Dransfield (1986a) noted that B. aethiopum was generally “more massive” than B. flabellifer and for several characters, this does appear to be the case. The leaves have wider petioles with longer spines and more leaflets, and the staminate and pistillate rachillae are longer with more flowers. However, while B. aethiopum and B. flabellifer are at opposite ends of the size range for some characters, other Borassus species are intermediate and no truly determinate quantitative characters were identified. The Madagascar endemic B. sambiranensis is placed here in synonymy with B. aethiopum as the two are almost indistinguishable, both in the field and the herbarium. Jumelle and Perrier de la Bâthie (1913) describe in detail the differences between the two Madagascar taxa and state that B. sambiranensis is most similar to B. aethiopum. Beccari (1912 – 14, 1914, 1924) recognised B. sambiranensis, though only the pyrenes were available for him to examine. He wrote that they resemble B. aethiopum var. bagamojensis Becc. and differ only in that there is a deep hollow at the apex. The morphology of Borassus pyrenes is extremely variable and this character alone is insufficient to warrant continued recognition of B. sambiranensis. No type specimen was cited by Jumelle and Perrier de la Bâthie, though it could be Perrier 12069 (lower Sambirano valley) (Dransfield & Beentje 1995a). However, this specimen could not be located and a modern neotype, collected in the Sambirano valley, has been designated. Borassus deleb was placed in synonymy with B. aethiopum by Dransfield (1986a), as the diagnostic fruit characters of the former fit within the range of variation exhibited by the latter. Due to their large size and fleshy consistency, few whole Borassus fruits are preserved in European herbaria. New taxa were erected on the basis of differences between these fruits without taking into account the full range of natural variation. In an attempt to counter this problem, every fruit from three Kenyan specimens of B. aethiopum (159 fruits total) was measured in the field. The variation exhibited by those fruits already encompassed almost all the variation in fruit size for the whole genus. The fruit and leaf that are illustrated as part of the type of B. deleb are not significantly different from those of B. aethiopum. Based on my own field observations and examination of the type specimen, I agree with the conclusions of Dransfield (1986a) to place B. deleb in synonymy under B. aethiopum. A neotype has been designated for B. aethiopum as the holotype is missing (Hepper 1976). The holotype was collected in Ghana near Accra (Thonning & Schumacher 1829). The neotype was also collected near Accra and includes both staminate and pistillate elements. (R.P. Bayton. 2007)/Palmweb.

Culture

Comments and Curiosities

Borassus aethiopium is a dioecious palm species native to Africa where it grows in savannas and woods. The name is Latinized for 'Ethiopian' where the species is known; it is commonly called palmyra palm, as are all the plants in the genus.

Etymology: ‘Aethiopia’ was a general term used by the ancient Greeks and Romans for Africa south of Libya and Egypt. (R.P. Bayton. 2007).

In English it is variously referred to as African fan palm, African palmyra palm, deleb palm, ron palm, toddy palm, black rhun palm, ronier palm (from the French) and other names. It also has names in African languages. The tree has many uses: the fruit are edible, as are the tender roots produced by the young plant;[1] fibres can be obtained from the leaves; and the wood (which is reputed to be termite-proof) can be used in construction. There are at least two varieties of this species: var. bagamojensis and var. senegalensis.

Conservation: Least concern. Borassus aethiopum is widespread and common in a number of African countries. While several populations are in decline (Sambou et al. 1992; 2002), the palm remains common. Borassus sambiranensis is listed by the IUCN as endangered (EN A1c) due to habitat loss/degradation and suppression of regeneration by fire. It is perhaps unfortunate that by placing this taxon in synonymy with the widespread B. aethiopum, the conservation status of the Madagascar populations will be masked. (R.P. Bayton. 2007)/Palmweb.

Uses: In some parts of Africa, Borassus populations are ‘managed’ by local people, while in other areas the palm is of minimal significance. In many areas, Borassus aethiopum is restricted to game reserves and national parks where it is outside the reach of local people. The leaves are used for thatch and weaving, though species of Hyphaene are generally preferred. The palm is tapped for wine, though the process is different from that used in Asia as the apical bud is tapped rather than the inflorescences. The fruits, undeveloped endosperm and cotyledonary stalks are consumed. Burkill (1997) has reviewed the uses of Borassus aethiopum in West Africa. (R.P. Bayton. 2007)/Palmweb.

External Links

References

Phonetic spelling of Latin names by edric.

Special thanks to Geoff Stein, (Palmbob) for his hundreds of photos, edric.

Special thanks to Palmweb.org, Dr. John Dransfield, Dr. Bill Baker & team, for their volumes of information and photos, edric.

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).

Bayton, R.P.2007. A revision of Borassus L. (Arecaceae). Kew Bulletin 62: 561-586.

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