Borassus heineanus Becc.

Bayton, R. (2007). A Revision of Borassus L. (Arecaceae). Kew Bulletin, 62(4), 561-585. Retrieved from http://www.jstor.org/stable/20443389

Type

Papua New Guinea, Sepik River, Heine s.n. (holotype FE!).

Morphology Stem

Stem to 25 m tall, stem diameter unknown

Morphology Leaves

Leaves 20 - 28 in the crown; petiole and sheath 150 - 300 cm long; petiole 3.1 - 5.2 cm wide at midpoint, green with very sharp black margins, but no spines; costa 130- 150 cm long; adaxial hastula conspicuous, to 1.2 cm, abaxial hastula absent; lamina radius to 180 cm maximum; leaflets 50 - 90, 3.9 - 7.1 cm wide, apices bifid and cuspidate, shortest leaflet 110 - 130 cm long, leaf divided to 76 - 92 cm; commissural veins 3 - 6 per cm, leaf anatomy dorsiventral.

Morphology Reproductive morphology Inflorescences

Pistillate inflorescences spicate; flower bearing portion 37 - 49 cm long with 7 - 22 flowers arranged spirally Staminate inflorescences branched to one order, upper subtending branches terminating in 1 rachilla; rachillae brown and catkin-like, ± 70 cm long, 2.7 - 4.3 cm diameter; rachilla bracts forming pits containing a cincinnus of 6 - 12 flowers.

Morphology Reproductive morphology Flowers

Staminate flowers exserted from pits individually, 0.4 - 1 cm long, bracteoles 1 x 1 cm; calyx 0.3 x 0.8 cm, shallowly to deeply divided into three sepals, petal lobes 0.2 x 0.1 cm; stamens 6 with very short filaments, 0.11 x 0.15 cm, anthers 0.18 x 0.06 cm; pistillode distinct, 0.2 - 0.5 x 0.02 cm Pistillate flowers 2.5 x 2 cm; bracteoles large, 1.5 cm diam., sepals 1.5 x 2 cm, petals 1.0 x 1.5 cm

Morphology Reproductive morphology Flowers Pollen

Pollen monosulcate, elliptical, 51 - 70 μm long, aperture 41 - 63 μm long, polar axis 37 - 57 μm long; tectum perforate, sparsely covered with supratectal gemmae

Morphology Reproductive morphology Fruits

Fruits large, 12 - 15 x 8 - 10 cm, ovoid with a slightly pointed apex, greenish black; pyrenes 1 - 3, 9.2 - 10.5 cm x 4.8 - 7.0 cm x 4.0 - 4.5 cm; endocarp sometimes with flanges that penetrate the seed.

Distribution

Endemic to New Guinea. Occurring in both Papua New Guinea and Indonesian Papua, but restricted to the northern side of the island.

Ecology

Tropical rain forest on alluvial sands (Barfod et al. 2001). The palm may also be cultivated (Kjær 2003).

Conservation

Data deficient. Borassus heineanus has been collected in only seven locations in New Guinea. Kjær (2003) reported a stand of approximately 300 x 300 metres in an area by the Sepik River in Papua New Guinea. Additional localities may exist, and further collections are needed.

Vernacular

Beiwof (Apau), Lipmemon (Kamangauwi dialect).

Note

Borassus heineanus is by far the most distinctive species in the genus and this led Beccari (1924) to speculate that it should be transferred into Borassodendron. Both B. heineanus and Borassodendron occur in humid rain forest, generally an atypical habitat for Borassus. Unlike all other Borassus species, the petiole is always unarmed, the leaves have a dorsiventral leaf anatomy and cuspidate leaflet apices, the staminate inflorescence branches to one order only and the staminate flowers have a large pistillode. However, the pollen is very similar to that found in the other Borassus species; it has a sulcate aperture that is almost the length of the grain and a perforate tectum with sparse supratectal gemmae. In contrast, the pollen of Borassodendron has a porate aperture and no gemmae (Ferguson et al. 1986). Preliminary results from the molecular study confirm the monophyly of Borassus in its current circumscription (including B. heineanus) and suggest that Borassodendron is sister to Borassus (Bayton 2005). The pyrenes of Borassus heineanus are rather unusual for the genus. In most Borassus species, pyrene length and breadth are similar or equal, but in B. heineanus, the pyrenes are much longer than wide. While living material of B. heineanus has never been collected outside New Guinea, two endocarps (Degener & Degener 24625, BH) found on a beach on the Pacific island of Canton (Phoenix Is., Kiribati) were identified as belonging to Borassus (Degener & Degener 1974) and are probably attributable to this species. The endocarps are rather long and narrow and have perpendicular internal flanges (see Gunn & Dennis 1976: 177). These characters set them apart from all other Borassus species. However, typical endocarps of B. heineanus have a small hole in the apex to allow the cotyledonary stalk to exit. The Canton endocarps have deep V-shaped clefts at the apex, usually filled with black fibres (fibres eroded in one pyrene). There is a great deal of natural variation in the endocarps of better-known Borassus species. Perhaps when more material is collected in New Guinea, the presence of internal flanges or apical V-shaped clefts in the endocarp will fit into the natural range of variation exhibited by B. heineanus. After Georg Heine, administrator with the German New Guinea Company, who collected the type specimen.

Use

Very little is known about the uses of B. heineanus, though Kjær (2003) reports that the leaves are used for thatch.