Grass Phylogeny Working Group FNA 25: 13-14

Plants annual or perennial, usually synoecious, sometimes monoecious or dioecious; habit varied. Culms usually annual, sometimes becoming somewhat woody, internodes solid or hollow. Leaves sometimes conspicuously ditichous; sheaths usually open; auricles  absent; abaxial ligules usually absent, sometimes present as a line of hairs; adaxial ligules membranous, often ciliate with cilia longer than the membranous base, sometimes not ciliate; blades not pseudopetiolate; mesophyll usually radiate; adaxial palisade layer not present; fusoid cells absent; arm cells absent; Kranz anatomy present; midribs simple; adaxial bulliform cells present; stomatal subsidiary cells dome-shape or triangular; bicellular microhairs present, usually with a short, wide, apical cell; papillae sometimes present. Synflorescences ebracteate, paniculate, racemose, or spicate (occasionally of a single spikelets, often a panicle of spikelike branches; disarticulation usually beneath the florets, sometimes at the base of the primary branches. Spikelets usually bisexual, usually laterally compressed, with 1-60 florets, distal florets often reduced. Glumes usually 2, shorter of longer than the lemmas, sometimes exceeding the distal florets, lower or both glumes occasionaaly absent; lemmas lacking uncinate hairs, sometimes awned, awns single or, if multiple, the bases not fused into a single column; anthers 1-3; ovaries glabrous; styles 2, separate throughout, bases close together. Caryopses often with a free or loose pericarp; hila short; endosperm hard, without lipid; starch grains simple or compound; haustorial synergids absent; embryos usually large relative to the endosperm, not waisted; ambryonic leaf margins usually meeting, rarely overlapping. x = (7, 8) 9, 10 (12).

Chlroidoideae  are most abundant in dry, tropical and subtropical regions. In North America, it reaches if greatest diversity in the southwest United States. All but a few southern African species employ a C₄ photosynthetic pathway. Most employ either he NAD-ME or PCK pathways, but Pappophorum uses the NADP-ME pathway. 

All recent work has supported the monophyly of thesubfamily as circumscribed here. There is less agreement concerning its closest relative and considerable disagreement concerning its internal structure.