Oligostachyum

HABIT Perennial. Rhizomes absent (3), or elongated (13); leptomorph (13/13). Culms erect (7/7); 76–410.8–1300 cm long; firm (2), or woody (14); without nodal roots (1/1). Culm-internodes terete (14), or semiterete (1), or channelled (2). Culm-nodes flush with internodes (1/7), or swollen (5/7), or flanged (1/7); with distinct supra-nodal ridge (4/4). Lateral branches dendroid. Branch complement three (12/14), or several (3/14); in a horizontal line (2/2); with subequal branches (3/8), or 1 branch dominant (5/8); thinner than stem (4/4). Culm-sheaths tardily deciduous (4/7), or deciduous (3/7); without auricles (9/13), or auriculate (4/13). Culm-sheath blade linear (2/12), or lanceolate (8/12), or narrowly ovate (1/12), or triangular (3/12); as wide as sheath at base (1/1). Leaf-sheath auricles absent (12), or erect (1), or falcate (5). Ligule an eciliate membrane (5), or a ciliolate membrane (11). Leaf-blade base with a brief petiole-like connection to sheath. Leaf-blades persistent (10), or deciduous at the ligule (6); linear (3), or lanceolate, or oblong (2); herbaceous (15), or chartaceous (1). Leaf-blade venation without cross veins (12), or with distinct cross veins (4).

INFLORESCENCE Synflorescence simple (8/12), or bractiferous (4/12); fasciculate (4/4); with glumaceous subtending bracts (1/4), or spathaceous subtending bracts (3/4); without axillary buds at base of spikelet (3/4), or with axillary buds at base of spikelet (1/4). Inflorescence a panicle (2/8), or composed of racemes (6/8); subtended by an unspecialized leaf-sheath (7/8), or a spatheole (1/8).

Panicle open (1/1).

Racemes single (4/4); bearing few fertile spikelets (3/6), or many spikelets (3/6); bearing 2 fertile spikelets on each (2/3), or 3 fertile spikelets on each (3/3), or 4 fertile spikelets on each (1/3).

Spikelets solitary (8/8). Fertile spikelets sessile (1/12), or pedicelled (11/12).

FERTILE SPIKELETS Spikelets comprising 3–4 fertile florets (1/9), or 5 fertile florets (4/9), or 6–7 fertile florets (7/9), or 8–9 fertile florets (5/9), or 10 fertile florets (4/9), or 11 fertile florets (3/9), or 12–13 fertile florets (2/9); with diminished florets at the apex (12/12). Spikelets linear (9/12), or lanceolate (2/12), or elliptic (1/12); laterally compressed (12/12); 15–46–80 mm long; breaking up at maturity (12/12); disarticulating below each fertile floret (12/12). Rhachilla internodes definite (12/12); glabrous (6/12), or pubescent (4/12), or pilose (2/12).

GLUMES Glumes two (9/12), or several (6/12); persistent (12/12); shorter than spikelet (12/12). Lower glume lanceolate (7/11), or elliptic (4/11); 0.5–0.75–1 length of upper glume; chartaceous (11/11); without keels (1/5), or 1-keeled (4/5); 7–9 -veined (1/1). Lower glume lateral veins obscure (1/12), or distinct (11/12). Lower glume surface smooth (9/12), or asperulous (2/12), or scabrous (2/12); without pits (12/12). Lower glume apex obtuse (1/8), or acute (3/8), or acuminate (4/8); muticous (10/11), or mucronate (1/11). Upper glume lanceolate (2/11), or elliptic (5/11), or ovate (4/11); chartaceous (11/11); without keels (2/5), or 1-keeled (3/5); 7–8 -veined (2/4), or 9 -veined (4/4), or 10–11 -veined (1/4). Upper glume primary vein eciliate (11/12), or ciliolate (1/12). Upper glume surface smooth (9/12), or asperulous (2/12), or scabrous (2/12). Upper glume apex obtuse (1/9), or acute (7/9), or acuminate (1/9); muticous (10/11), or mucronate (1/11).

FLORETS Fertile lemma lanceolate (1/11), or elliptic (3/11), or ovate (7/11); chartaceous (12/12); without keel (12/12); wingless (12/12); 7–8 -veined (2/7), or 9–11 -veined (4/7), or 12 -veined (2/7), or 13 -veined (4/7), or 14 -veined (1/7), or 15 -veined (2/7), or 16 -veined (1/7). Lemma lateral veins obscure (1/1). Lemma surface smooth (7/12), or asperulous (2/12), or scabrous (3/12); unwrinkled (12/12); without grooves (12/12); glabrous (9/12), or puberulous (1/12), or pilose (2/12). Lemma margins eciliate (8/12), or ciliolate (3/12), or ciliate (2/12). Lemma apex obtuse (1/12), or acute (3/12), or acuminate (7/12), or setaceously attenuate (1/12); muticous (7/12), or mucronate (3/12), or awned (2/12); 1 -awned (2/2). Palea membranous (11/12), or chartaceous (1/12); 2 -veined (2/4), or 9 -veined (1/4), or 15 -veined (1/4). Palea keels eciliate (2/12), or ciliolate (4/12), or ciliate (6/12). Palea surface glabrous (10/12), or pubescent (2/12). Apical sterile florets resembling fertile though underdeveloped (12/12).

FLOWER Lodicules 3 (12/12), or several (1/12); glabrous (6/12), or ciliate (6/12). Anthers 3 (12/12), or 4–5 (2/12). Stigmas 2 (2/12), or 3 (11/12). Ovary unappendaged (9/12), or umbonate (3/12); glabrous (7/7), or pubescent on apex (1/7).

FRUIT Caryopsis with adherent pericarp (8/8); apex unappendaged (4/4).

DISTRIBUTION Temperate Asia.

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