Plectocomiopsis songthanhensis A.J.Hend. & N.Q.Dung, 2010

Henderson, Andrew & Dung, Nguyen Quoc, 2010, Notes on rattans (Arecaceae) from Vietnam, Phytotaxa 8, pp. 25-33 : 25-27

Plectocomiopsis songthanhensis A.J.Hend. & N.Q.Dung , sp. nov. ( Plate 1 )

A Plectocomiopsis geminiflora pinnis glabris et floribus glabris 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 3573 (holotype: HN!, isotypes: AAU! K! NY!) .

Stems clustered, forming large clumps, 20–30 m tall, 1.5–1.7 cm in diameter with sheaths, triangular in cross–section. Leaf sheaths green or gray-green, with few, scattered, yellowish spines to 5 mm long; knees absent; ocreas to 1 cm long, green, membranous, with few, short spines, becoming brown and splitting irregularly; petioles absent or to 2 cm long; rachis 56–87 cm long, with recurved spines abaxially; pinnae 11– 13 per side of rachis, more or less regularly and distantly arranged; middle pinnae 25–27 cm long, 1.5–3 cm wide at widest point, lanceolate, with long, filiform apices, with prominent cross–veins, without bristles; cirri 60–80 cm long. Inflorescences 9–11 at apex of stem, subtended by reduced leaves, branched to 2 orders, pendulous; staminate inflorescences with 19–29 rachillae, these 9–23 cm long, 1.5 mm in diameter; staminate flowers borne in short, congested rows on opposite sides of rachillae to 1 cm long; staminate flowers globose in bud, 1.2 mm long (immature); sepals glabrous, 1 mm long; petals 3, free, valvate, glabrous, 1 mm long; pistillate inflorescences with 11 rachillae, these 7–12 cm long, 2.5 mm in diameter; pistillate flowers paired on very short rachillae subtended by a cupular bracteole; pistillate flowers not seen; fruits depressed–globose, 1.6–1.8 cm in diameter, brownish–green; endosperm homogeneous.

Distribution and habitat:— Endemic to central Vietnam in Quang Nam and Thua Thien-Hue Provinces, in disturbed places by roads or in disturbed areas in forest.

Local names and uses:— may phun, may rut. The cane is of poor quality and is collected only for domestic uses.

Additional specimens examined (paratypes):— VIETNAM. Thua Thien-Hue: Bach Ma National Park , 16°14’N, 107°52’E, ca. 100 m, 14 April 2007, Henderson et al. 3277 ( HN, NY) . Quang Nam: Nam Giang district, 17 October 2005, N. K. Ban PA 167 ( HN); 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, Henderson et al. 3571 ( AAU, HN, K, NY); 3572 ( AAU, HN, K, NY); 14 Mar 2009, 3577 ( AAU, HN, K, NY); 3581 ( HN, K, NY); Ho Chi Minh Highway between Thanh My and Prao, 15˚48’ N, 107˚45’ E, 294 m, 19 March 2009, Henderson et al. 3594 ( HN, NY) .

Discussion: — Plectocomiopsis songthanhensis (named for the Song Thanh Nature Reserve) differs from P. geminiflora in its pinnae without bristles (versus pinnae with conspicuous bristles along adaxial mid–veins and margins); short, entire, non-tattering ocreas (versus elongate, tattering ocreas); petioles without marginal spines (versus petioles with marginal spines); staminate calyces split to the base into 3, free sepals (versus staminate calyces cupular, briefly and irregularly 3–lobed); and glabrous staminate and pistillate perianths (versus staminate and pistillate perianths usually covered with scale–like trichomes).

The distributions of the two species do not overlap. Plectocomiopsis songthanhensis is known only from central Vietnam in Quang Nam and Thua Thien–Hue Provinces. In Vietnam, P. geminiflora is known only from southern part of the country, in Dong Nai and Lam Dong Provinces, although it is widely distributed elsewhere ( Cambodia, Laos, Myanmar, Thailand, Borneo, Peninsular Malaysia, and Sumatra). Three specimens of Plectocomiopsis at K (Khamphone 393, 409, Sounthone 22) from Laos occur relatively near to the population of P. songthanhensis . Although all three specimens are sterile, they share bristly pinnae, tattering ocreas, and spiny petioles, and are identified as P. geminiflora (Evans et al. 2002) .

Figures

PLATE 1. Plectocomiopsis songthanhensis. Left—habit. Right—fruits.