Gigantochloa sp. (TH: Songkhla: Khao Daeng)

Characteristics: Habit tight caespitose. Rhizome pachymorph, short-necked [n.v.]. Culms straight, over 8 m tall [ultimate length not yet known], stiffly erect, slightly bending above. Young shoots green, glabrous, with erect culm-leaf blades; emerge from July/August (or earlier?). Culm-internodes terete, 27–33 cm long, green, without streaks, smooth, glabrous, but occasionally scattered with a few short black appressed hairs just below nodes with the surface becoming rough later; not farinose; diameter 3.5 cm [ultimate diameter not yet known]; thick-walled. Culm-nodes flat, glabrous, smooth; sheath scar not prominent, occasionally with a narrow white farinose ring below the sheath scar, fading early; supranodal line obscure but discernible, with or without a slight ridge; aerial roots none. Branch-buds solitary, from the basal node up. Branches initially 3, the central one dominant, long; unbranched on the basal and lower culm; branching intravaginal, all branches rebranching. Culm-leaves deciduous on branched nodes, persistent on the basal and lower unbranched nodes, and decaying on the culm. Culm-leaf sheaths 11–13 cm wide at the base, 14–20 cm long, slightly longer than half the length of the internode, thickly papery, greenish to pale pinkish when young, white to pale straw-colored when dry, occasionally scattered with short black appressed hairs, otherwise glabrous and smooth; margins short black ciliate when young; apex asymmetrical, triangular-truncate (from about the 4th basal sheath up, the apex of the lower sheaths is horizontally truncate or convex) with slightly raised edges, the triangular middle part about 2.5–3.5 cm wide and connected with the blade, each edge 1.5–2 cm wide and bearing the auricles. Culm-leaf auricles conspicuous, oval-shaped, 1–1.5 cm wide, 0.4–0.8 cm high, blackish when young, entire, without bristles. Culm-leaf ligule rather wide, extending at the sheath apex from edge to edge, width 5 cm and more, 2–4 mm high, somewhat higher toward the edges, fringed, ligule and fringes brown when young, fringes extending into fine several mm long white caducous bristles. Culm-leaf blades papery, persistent or late caducous, stiffly erect, long-triangular, apex long-acuminate, about half to three-quarters as long as the sheath length, dark brown when young, white to pale straw-colored when dry. Foliage-leaves (6–) 8 (–10) per branchlet. Foliage-leaf sheaths keeled, green, smooth, glabrous or nearly so. Foliage-leaf auricles of variable size, 2 mm long or smaller, rounded, entire, eciliate. Foliage-leaf ligule conspicuous, 6–10 (15) mm long, entire, pointed, pale brownish green when young, becoming lacerate when dry. Foliage-leaf blades large, 30–40 (56) × 2.5–5 (8) cm, linear-lanceolate, green, glabrous on both surfaces; base rounded to wedge-shaped; apex attenuate; margins antrorsely scabrous; midrib proximally prominent on both surfaces, light green beneath; pseudopetiole 2–3 mm long. Flowers and seeds are unknown.

Provisional identification: Similar to Gigantochloa ligulata, but internodes are glabrous, ligules are shorter, culm-leaf blades are long-triangular, and foliage-leaf blades are glabrous beneath.