Areca songthanhensis A.J.Hend., N.K.Ban & B.V.Thanh

Henderson, Andrew, Ban, Ninh Khac & Thanh, Bui Van, 2010, New species of Areca, Pinanga, and Licuala (Arecaceae) from Vietnam, Phytotaxa 8, pp. 34-40 : 34-36

Areca songthanhensis A.J.Hend., N.K.Ban & B.V.Thanh , sp. nov. ( Plate 1 )

A Areca triandra caulibus solitarius foliis paucijugus et triadibus dispositis differt.

Type:— VIETNAM. Quang Nam Province: Nam Giang District, Ta Bhing commune, Song Thanh Nature Reserve , road 14 D to Laos, 15˚39’ N , 107˚36’ E, 412 m. 12 March 2009, A . Henderson , B. V . Thanh , N. T . Vu & C . Tuo 3569 (holotype: HN!, isotypes: K! NY!) .

Stems solitary, 1.2–1.5 m tall, 2 cm in diameter, green, without scales. Sheaths closed, forming crownshafts, 14–25 cm long, green; ocreas 1 cm long, early deciduous; petioles 13 cm long; rachises 47–49 cm long; pinnae 4–5 per side of rachis, middle pinnae 32–34 cm long, 7–9 cm wide at the middle, apical pinnae 16–21 cm long, 6–8 cm wide at the middle, praemorse. Inflorescences infrafoliar, erect, branched to 2 orders; peduncles 0.5–1.5 cm long, 0.5 cm wide; prophylls 13 cm long, splitting abaxially; rachises 6.5–9 cm long; proximal few first order branches of inflorescence have rachillae with staminate flowers only, other distal branches of inflorescence with a single pistillate flower borne at or very near the base, staminate flowers only distally; rachillae 43, 4– 7 cm long, glabrous; staminate flowers paired, borne on one side of the rachillae, 1.5 mm long, white; sepals 3, free, triangular, 0.7 mm long; petals 3, free, valvate, triangular, 1.4 mm long; stamens 3, dorsifixed; filaments 0.5 mm long; anthers sagittate, 0.7 mm long; pistillodes absent; pistillate flowers 1 per rachilla, borne at or very near the base of rachilla, 4.5 mm long; sepals 3, free, broadly imbricate, 4.5 mm long; petals 3, free, broadly imbricate, 4 mm long, beaked; fruits 3 cm long, 1.3 cm diameter, ellipsoid, beaked, red; endosperm ruminate.

Distribution and habitat: —Endemic to central Vietnam and known only from Quang Nam Province, growing in lowland forest at low elevations.

Local names and uses: —None recorded.

Additional specimen examined (paratype): — VIETNAM. Quang Nam: Nam Giang District, Ta Bhing commune, Song Thanh Nature Reserve , road 14 D to Laos , 15˚39’ N , 107˚36’ E, 412 m, 14 March 2009 , Henderson et al. 3580 ( HN, NY) .

Discussion: — Areca songthanhensis is similar to A. triandra but it is smaller in size, has solitary stems and fewer pinnae. The main difference, however, is in the inflorescences. In A. triandra the inflorescences are branched to three orders. Each rachilla has a single pistillate flower borne at the base ( Plate 1 ). Beyond this flower the rachilla is slender and bears only staminate flowers. Some rachillae on distal parts of the inflorescence lack a pistillate flower, but first order branches on proximal parts of the inflorescence always have several rachillae with pistillate flowers. In A. songthanhensis the structure of the inflorescences is different. Inflorescences are branched to two orders. The proximal few branches on the rachis, the only ones branched to two orders, bear rachillae with staminate flowers only. Distal to these on the rachis are rachillae with a single pistillate flower borne at or near the very base, such that the pistillate flowers appears to be borne directly on the rachis ( Plate 1 ).

This inflorescence structure of Areca songthanhensis bears a superficial resemblance to that of specimens determined as A. montana Ridley (1907: 136) from peninsular Thailand and peninsular Malaysia, although the two occur more than 1,000 km apart. However, the branching pattern of the inflorescences of these specimens is exactly the same as in A. triandra , and inflorescence size and number of pinnae overlap with A. triandra ( Lim & Whitmore 2001) . Because of this similarity in leaves and inflorescences, A. montana was placed as a synonym of A. triandra by Henderson (2009).

Figures

PLATE 1. Top left—habit of Areca songthanhensis. Top right—inflorescence of A. songthanensis, with proximal branch (arrowed) branched to two orders and bearing rachillae with staminate flowers only. Bottom left—infructescence of A. songthanensis. Bottom right—inflorescence of Areca triandra, with proximal branch (arrowed) branched to three orders and bearing rachillae with pistillate and staminate flowers.