Schizostachyum langbianense, a new species of bamboo (Poaceae: Bambusoideae) from Lang Bian Mountain, Vietnam Author Tien, Chinh Vu The Graduate University of the Chinese Academy of Science, 19 A Yuquanlu, Beijing, 100049, China; Author Xia, Nianhe Author Wong, Khoon Meng Author Van, Duy Nong Author Toan, Phan Nguyen Huu Author Nguyen, Hoang Nghia Author Tran, Van Tien text Phytotaxa 2016 2016-04-18 257 2 181 186 http://dx.doi.org/10.11646/phytotaxa.257.2.8 journal article 305722 10.11646/phytotaxa.257.2.8 0446ddbb-0818-4587-b003-d0bdb1ac8a32 1179-3163 13674598 Schizostachyum langbianense V.T. Tran, N.H. Xia & H.N. Nguyen , sp. nov . ( Figs. 1 , 2 ) TYPE:— VIETNAM . Lam Dong Province : Lac Duong District , Lang Bian mountain , 12002’ 654 ’ , 108026’ 278 ’’ , alt. 1879 m , 11 October 2008 , V.T. Tran & N.H. Nghia 460 ( holotype : VAFS ! ; isotypes : DLU ! , IBSC ! , SING ! ). It is similar to Schizostachyum ninhthuanense in having pseudospikelets with a few spikelets clustered on the short ultimate branchlets, but differs in having culm leaves where the apical portion of the sheath proper is horizontal or only slightly concave, culm leaf blades that are narrowly lanceolate, a palea apex which is not bifid and with the dorsal side furrowed between two keels. Rhizome pachymorph. Culms erect, 4–8 m tall, 2–4 cm diameter; internodes terete, straight, 55–60 cm long, when young covered with sparse soft hairs; wall 0.2–0.3 cm thick; nodes swollen, with a ring of white powder c. 0.5 cm broad below each node. Branches numerous at each mid-culm node, slender, subequal. Culm leaves oblong, densely covered with hairs on the outer surface at its base, 23–24 x 7–8 cm ; apical portion of sheath proper horizontal or only slightly concave; blade narrowly lanceolate, 8–14 x 0.7–0.8 cm , erect at first, then becoming reflexed; auricles low rims ca. 0.1 cm long, with 4–5 slender bristles ca. 0.4 cm long; ligule horizontal or subtruncate, short, 1–2 mm long, with fimbriae 2–4 mm long. Foliage leaves 4–5 per complement; sheaths often sparsely covered with white hairs; auricles inconspicuous, oral setae numerous, 2–4 mm long; ligule ca. 0.1 cm long; petiole ca. 0.3 cm long, ca. 0.15 cm thick; blades 20–22 x 2.5–3.5 cm , base rounded and oblique, adaxially and abaxially covered with sparse smooth hairs; margins minutely serrulate, 6–9 veins on each side of the midrib. Synflorescences ca. 1.3 cm long, pseudospikelets several clustered on the short ultimate branchlets, glabrous; prophylls ovate-lanceolate, 4–5 x 1.5–2 mm , thin, apex obtuse, two-keeled; bracts 1–3, oblong to oblong-lanceolate, upper 5–6 x 3–4 mm , papery, veins 11–13, apex obtuse to acute or mucronate; glumes absent; floret 1, fertile; rachilla internodes short, ca. 1–2 mm long; fertile lemma oblong–lanceolate, 9–10 x 4–4.5 mm , veins 11–13, apex acute, short-mucronate; palea ovate-lanceolate, 9–10 x 4–4.5 mm , involute, papery, dorsal surface of palea slightly furrowed between 2 keels, margins ciliate, apex acute (not bifid), short-mucronate, veins 11–13; lodicules 3, triangular or oblong, largest 2 x 1 mm , margins apically ciliate; stamens 6, ca. 5 mm long, connate at their base; anthers initially dull green, pale yellow when mature, ca. 2 mm long; style ca. 1.3 cm long; stigmas 3, purple, plumose. Fruit a nucoid caryopsis, ovoid-oblong, 5–6 x 2–3 mm , glabrous, with the persistent style base at its apex. Etymology:— The species epithet refers to Lang Bian Mountain. Morphological comparisons:— Schizostachyum langbianense has a few pseudospikelets in each cluster on the short ultimate inflorescence branchlets, and so resembles S. ninhthuanense ( Tran et al. 2010 ) found in the same geographical area. However, in contrast, the culm leaves of S. langbianense have a slightly concave or horizontal apical portion, culm leaf blades that are narrowly lanceolate, an acute (not bifid) palea apex, and a dorsal palea surface that is furrowed between 2 keels. The characters states considered important for distinguishing these species are given in Table 1 . FIGURE 1. Schizostachyum langbianense . A. Culm leaf showing reflexed blade. B. Apical portions of culm leaves with blade in natural reflexed position (left) and upturned (right). C. Nodal section of the culm showing the single bud. D. Nodal section of the mid-culm, showing subequal branches in young developing branch complement. E. Branch leaf complement. F. Part of branch leaf complement, showing pseudopetiole and ligule. G. Synflorescence including a developing fruit with persistent style and stigmas. H. Floret with exsert staminal complement. I. Floret, showing prophyll (lowermost structure), distally with 2 bracts, then a lemma and palea. J. Lodicules. Drawn by Tran Van Tien from V.T. Tran & N.H. Nghia 460 (VAFS!). FIGURE 2. Schizostachyum langbianense . A. Habitat. B. Clump base. C. Culm leaves showing erect blade (left), and reflexed blade (right). D. Upper or apical portion of culm leaf sheath proper. E. Nodal section of the culm, showing subequal branches in young complement. F. Nodal section of the culm showing the single bud. G. Branch leaf complement. H. Synflorescence showing pseudospikelets, and a detached floret. I. Prophyll (basal-most structure (Pr), and distally 2 bracts (Br), a lemma (L) and palea (Pl). J. Floret with staminal complement. K. Lemma. L. Dorsal view of palea with a furrow. M. Lodicules (Ld) and stamens (St). N. Purplish plumose stigmas (St) exsert from the tip of a floret. Photos by Tran Van Tien. Geographic distribution and Habitat:— This new species is only known from the type collection and its distribution area is not too far from the type locality of Schizostachyum ninhthuanense ( Fig. 3 ). Both of them occur on the Lang Bian Plateau, southern Vietnam , S. ninhthuanense being found in lower montane sites ( 400–1000 m a.s.l.), which is whereas the new species is found in higher elevations ( 1600–1900 m a.s.l.). S. ninhthuanense is found in open semi-deciduous and degraded forests, and S. langbianense is found in evergreen alpine forests or mixed broadleaved alpine forests, along valleys and mountain gorges. It is found in small populations, being apparently endemic to Lang Bian Mountain, Lac Duong District, Lam Dong Province , southern Vietnam . FIGURE 3. Geographical distribution of Schizostachyum langbianense (L) and S. ninhthuanense (N). Phenology:— Flowering and fruiting were observed in October 2008 and December 2009 , respectively. New culm shoots often appear from May to August.