POACEAE (GRAMINAE)

Annuals or perennial herbs or tall woody bamboos, sometimes with rhizomes and stolons. Stems erect, ascending or prostrate and creeping, usually branched at the base. Culms (flowering stems) jointed, cylindrical, rarely flattened, internodes fistular (hollow) or solid, nodes always solid; branches arising singly from nodes and subtended by a leaf sheath and 2-keeled prophyll, often fascicled in bamboos. Leaves solitary at nodes, sometimes crowded at base of the stems, alternate, distichous, consisting of sheath, ligule and blade. Leaf sheath surrounding and supporting culm-internode, split to base or tubular with partially or completely fused margins, frequently swollen at base, the shoulders sometimes extended upwards into triangular auricles, modified with reduced blade in bamboos (culm sheath). Ligule adaxial, placed at the junction of sheath and blade, membranous or reduced to a fringe of hairs (e.g., Phragmites), rarely absent (e.g., Echinochloa). Leaf blade divergent, usually long and narrow, rarely broad, usually passing gradually into the sheath, rarely with petiole like base (e.g., Saccharum), flat, convolute, involute or terete, veins parallel, sometimes with cross-connecting veinlets (in bamboos). Inflorescence terminal or axillary, an open, contracted or spike-like panicle, or composed of lax to spike-like racemes arranged along an elongate central axis, or digitate or paired or occasionally solitary; axillary inflorescences often many, subtended by spatheoles (specialised bladeless leaf sheaths) and gathered into a leafy compound panicle. Flowers small and inconspicuous, 1-many, borne in units termed as spikelets. Spikelets composed of distichous bracts arranged along a slender axis (Rachilla); typically 2 lowest opposing bracts, the Glumes, empty subtending 1-many florets arranged on rachilla. Florets composed of 2 opposing bracts enclosing a single small floret, outer bract (Lemma) clasping the more delicate, usually 2-keeled, inner bract (Palea); base of the floret often with thickened prolongation jointed with rachilla (Callus); lemma and sometimes glumes awned. Flowers bisexual or unisexual. Lodicules 2, small (representing perianth), rarely 3 or absent, 3-many in bamboos, hyaline or fleshy. Stamens 1-6, usually 3, hypogynous, filaments capillary, anthers bithecous, versatile, opening by a longitudinal slit or rarely by terminal and/ or basal pores. Ovary 1-locular with 1 anatropous ovule; styles 1-3, usually 2, free or united at base, stigmas feathery (plumes), exserted from apex or sides of floret. Fruit normally a dry indehiscent caryopsis (or grain) with thin pericarp firmly adnate to seed, rarely pericarp free, fleshy in some bamboos.

793 genera and about 12000 species