Borassus heineanus Becc., Webbia 4: 354 (1914)

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Content

Distribution

Map uses TDWG level 3 distributions (https://github.com/tdwg/wgsrpd)
New Guinea present (World Checklist of Arecaceae)B
Endemic to New Guinea. Occurring in both Papua New Guinea and Indonesian Papua, but restricted to the northern side of the island. (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Discussion

  • 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. In some specimens, the endocarp has a number of internal flanges that penetrate the seed. The flanges are perpendicular to the main endocarp wall and are only visible when the pyrene is viewed in transverse section. A sectioned pyrene in the type specimen does not have internal flanges. This character distinguishes Borassodendron (with internal flanges) from all other Borassus species and could indicate that a second unidentified Borassus species occurs in New Guinea. However, no additional morphological characters could be found to distinguish between specimens with or without internal flanges. The adaptive significance of these flanges is uncertain. 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. (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Biology And Ecology

  • Tropical rain forest on alluvial sands (Barfod et al. 2001). The palm may also be cultivated (Kjær 2003). (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Conservation

  • Data deficient. Borassus heineanus has been collected in only seven locations in New Guinea. Kjær (2003) reported a stand of approximately 300 × 300 metres in an area by the Sepik River in Papua New Guinea. Additional localities may exist, and further collections are needed. (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Etymology

  • After Georg Heine, administrator with the German New Guinea Company, who collected the type specimen. (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Common Name

  • Beiwof (Apau), Lipmemon (Kamangauwi dialect). (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Uses

  • Very little is known about the uses of B. heineanus, though Kjær (2003) reports that the leaves are used for thatch. (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Description

  • Stem to 25 m tall, stem diameter unknown. 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. 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. Pistillate inflorescences spicate; flowerbearing portion 37 – 49 cm long with 7 – 22 flowers arranged spirally. Staminate flowers exserted from pits individually, 0.4 – 1 cm long, bracteoles 1 × 1 cm; calyx 0.3 × 0.8 cm, shallowly to deeply divided into three sepals, petal lobes 0.2 × 0.1 cm; stamens 6 with very short filaments, 0.11 × 0.15 cm, anthers 0.18 × 0.06 cm; pistillode distinct, 0.2 – 0.5 × 0.02 cm. 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. Pistillate flowers 2.5 × 2 cm; bracteoles large, 1.5 cm diam., sepals 1.5 × 2 cm, petals 1.0 × 1.5 cm. Fruits large, 12 – 15 × 8 – 10 cm, ovoid with a slightly pointed apex, greenish black; pyrenes 1 – 3, 9.2 – 10.5 cm × 4.8 – 7.0 cm × 4.0 – 4.5 cm; endocarp sometimes with flanges that penetrate the seed. (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Materials Examined

  • INDONESIA. Papua Prov.: Jayapura Regency, Bernhard Camp, Idenburg River, April 1939, Brass 13775 (A, BRI, L); same date and locality, Brass 13945 (A, L) [Brass specimens verified by W. J. Baker]; Sarmi, 1 – 3 km N of Sewan on Waske River, 1 June 1993 (♀), McDonald & Ismail 3763 (CANB!, K!). PAPUA NEW GUINEA. East Sepik Prov.: Angoram sub-district, ca. 5 miles N of Timbunke on track to Kwoiwut, 12 Sept. 1959 (♀), Pullen 1719 (CANB!); 15 km N of Sepik River, between Timbunke & Angoram, 19 April 2000 (♀), Kjær 525 (AAU!); Morobe Prov.: cultivated, Papua New Guinea Forest Research Institute, Lae, Oct. 2001 (♂), Banka s.n. (K!, LAE); West Sepik Prov.: Beisom Non by Bitro Creek, ca. 12 km from Bitro village, 30 Nov. 1996 (♀), Ferrero 420 (AAU!); Green River, ca. 5 km downstream from Beimap, 30 Nov. 1996 (seedling), Ferrero 422 (AAU!); Green River District, Bitro village, 30 Nov. 1996 (♀ & ♂), Ferrero 423, 424 (AAU!) (Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae))A

Bibliography

    A. Bayton, R.P. 2007: A revision of Borassus L. (Arecaceae)
    B. World Checklist of Arecaceae