Annual or perennial herbs, or rarely with woody stems, often with rhizomes or stolons, mostly tufted with basal leaves; sometimes creeping; rarely climbing, rarely amphibious or aquatic. Aerial stems (culms) usually hollow except at the nodes. Leaves alternate, solitary at the nodes, with the base modified to form an open sheath which encloses the stem; blade usually with parallel venation, rarely with a distinct midrib, linear or lanceolate, tapering towards the tip, flat or inrolled: ligule present at the junction of the sheath and blade and consisting either of a membranous flap which is sometimes cleft or ciliate, or of a few to several hairs or papillae or absent (Fig. 47 a–b). The basic unit of the inflorescence is the spikelet which is analogous to the flower of other inflorescences. Spikelets pedicellate or sessile, arranged in spikes racemes panicles or irregular clusters (Fig. 47 e–h) and with 2 (rarely 1) basal sterile glumes and 1–many florets arranged on a narrow axis or rhachilla which is sometimes prolonged at the tip of the spikelet. Florets consisting of 2 bracts: the (fertile) lemma (outer and lower) and the palea which surround the flower (Fig. 48 a-c). Flowers usually bisexual (rarely unisexual when the plants are either monoecious or dioecious). Perianth represented by 1–3 (usually 2) lodicules or absent. Stamens usually 3, hypogynous; filaments long; anthers versatile. Ovary 1-locular, with 1 laterally inserted ovule; styles 2, with feathery stigmas (rarely the stigmas connate). Flowers sometimes abortive or male, when the subtending lemmas are referred to as sterile lemmas or staminate (or male) lemmas respectively. Glumes, lemmas, sterile lemmas and rarely paleas sometimes bear branched or unbranched awns attached terminally, dorsally, basally or in the base of a terminal notch (Fig. 48 d). At maturity the spikelets break up in one of two ways; either the rhachilla disarticulates above the glumes which remain at the tip of the pedicel after the florets have fallen (sometimes also disarticulating between the lemmas as well), or the disarticulation occurs below the glumes and the spikelets fall whole with the glumes attached (Fig. 48 c). Fruit a caryopsis often referred to as a grain ) usually enclosed by the lemma, rarely free. Endosperm large. C. 668 gen., cosmop.Unless specifically stated in the text:(a) the lengths of the glumes and lemmas do not include the awns; awn lengths are stated separately;(b) the lengths of the spikelets are measured from the base of the glumes to the tips of the awns;(c) the lengths of the inflorescence are measured from the lowermost branch of the inflorescence (or the base of the lowermost spikelet for unbranched inflorescences) to the tip of the inflorescence.