Dendrocalamus phuthoensis H.N. Nguyen, V.T. Nguyen et V.L. Le, 2017

Dendrocalamus phuthoensis H.N. Nguyen, V.T. Nguyen et V.L. Le View in CoL , sp. nov. (figs. 1, 2)

Diagnosis: —It is similar to D. longiligulatus in having pseudospikelets with florets closing when mature, but differs culm sheath glabrous, serrulate ligule of culm sheath 6–7 mm long, culm with densely brown pubescence when young, floret 7–9, palea 12–14mm long, 3 or 4 veins between and without veins on either side of keels (see table 1)

TYPE:— VIETNAM. Phu Tho Province: Yen Lap District, My Luong Commune, Vinh Thinh Village , 21029.754 ’, 104056.690 ’, elev. 41 m, 12 August 2010, V.T. Nguyen NVT062 (holotype: VNMN! , isotypes: Herbarium of Vietnamese Academy of Forest Sciences ( VAFS)! , Forest Science Centre for Central Northern Vietnam of VAFS ( FSCC)! ).

Arborescent bamboo, rhizomes pachymorph, short-necked. Culms erect, 18–20m tall, 13–17 cm diameter, apex nodding; internode terete, 20–34 cm long, wall 2–2.5cm thick, initially thinly white powdery and densely brown pubescent, becoming glabrous with age, sheath scars brown villous, with a 2 mm high ring of yellowish hairs above sheath scar, glabrous below the nodes; basal nodes non-prominent. Branches several, central axis dominant; branching developing from 18–20 nodes upwards on the culm, 7–8 m above ground. Culm sheaths caducous, glabrous, 30.5– 34.5× 37–42.5 cm, margins ciliate; ligule 6–7mm long, truncate or slightly concave, serrulate; auricles small, ca. 5 × 0.5–1 mm, reflexed, glabrous; blade reflexed, ca. 1/5 as long as sheath proper, adaxially brown hairy, abaxially glabrous, apex acuminate, margins setose. Leaves (10–)12–14 per ultimate branchet; sheath white-hairy; auricles absent; ligule truncate ca. 3 mm long, serrulate; petiole ca. 4 × 1.5–2 mm;leaf blade oblong-lanceolate, 26–40 × (3–) 5–7 cm, base nearly rounded, abaxially glabrous, adaxially villous and rough, secondary veins 11–12 pairs. Inflorescence iterauctant, flowering branch with leaves, pendulous, with (1–)2–15 clustered pseudospikelets at each node; pseudospikelets ovate-lanceolate, 15–18 × 5–6 mm, brown; florets 7–9, all florets fertile and each floret closed when mature; rachillainternodes short and not disarticulating; prophyll triangular, 3–4× 1.5–2 mm, 1–keeled, margins and keel dense long-ciliate, apex blunt. Glumes 1–2(–4), 6–6.4 mm long, pubescent, margins long ciliate, apex blunt; lemmas broadly ovate, (6.5–)8.3–11.2 × (5.8–) 8.1–9.2 mm, abaxially sparsely pubescent, adaxially glabrous, many-veined, margin long-ciliate, apex acute or obtuse; palea narrowly lanceolate, 10.5–14.7 × 4.2–4.8 mm, 2–keeled, 3–4-veined between keels and without veins on each wing, both sides pilose, apex bifid, margin long-ciliate; lodicules absent. Stamens 6, anthers yellow, 6.5–7.9 mm long, anthers exserted when mature, apex acute, with several white hairs; filament free. Ovary narrowly lanceolate, hairy, base with stalk ca. 3.8–4.8 mm, glabrous; stigma 1, hairless; pistil 12.4–15.7 mm long. Flowering in August, fruits unknown.

Etymology: —The specific epithet refers to Phu Tho Province, where the type material was collected.

Distribution and habitat:—This species is cultivated in My Luong commune,Commune, Yen Lap District, Phu Tho Province, Vietnam. The flowers as well as other material were collected from cultivated clumps in Vinh Thinh and Dong Ve Villages, My Luong Commune, Yen Lap District, Phu Tho Province, Vietnam on 12 August 2010 and 8 July 2016 ( Fig. 3 View FIGURE 3 ). Shoot season is from August to October.

Local Uses:—This species is economically valuable to the local people. Its shoot can used for food, and the culms are often used for house construction and general household use, and can be used a raw material for paper-pulp production.

Vernacular name: —Cây Đóng, Mai thông đốt.

Relationships: — Dendrocalamus phuthoensis is placed in subgen. Sinocalamus in the characters of pseudospikelets with many florets, basal nodes of culm without branches, and big leaves. This species may be more or less close to several species of subgen. Sinocalamus by each floret closing when mature, particular to D. longiligulatus , a species discovered in the close area. D. phuthoensis is similar to D. longiligulatus in the sheath scars not prominent, one main branch, basal nodes of culm without branches, auricles of culm sheath small, blade of culm sheath reflexed, auricules of leaf absent. However, the new species differs from the latter by having many florets, big leaves, glabrous culm sheath, culm internodes covering densely brown pubescences, and palea without veins on wings.

Additional specimens examined (paratypes): — VIETNAM. Phu Tho: Yen Lap District, My Luong Commune, Dong Ve Village , 21028,976 ’N, 104056.894 ’E, elev. 36 m, 12 August 2010, V.T. Nguyen NVT71 ( VAFS, FSCC) ; Yen Lap District, My Luong Commune, Vinh Thinh Village , 21029 ’46.9"N, 104056 ’41.3"E, elev. 41 m, 8 July 2016, H. N. Nguyen, V. T. Nguyen NVT355 ( VAFS, FSCC) .