Grass Phylogeny Working Group FNA 24: 57-58

Plants annual or perennial; sometimes matlike, sometimes cespitose, sometimes stoloniferous, sometimes rhizomatous. Culms usually hollow, sometimes solid. Leaves distichous; sheaths usually open to the base, varying to closed for nearly their full length; auricles present or absent; abaxial ligules absent; adaxial ligules scarious or membranous, sometimes puberulent, usually not ciliate, cilia sometimes shorter than the base; pseudopetioles rarely present; blades usually linear, sometimes broadly so, venation parallel; cross sections non-Kranz, mesophyll nonradiate, adaxial palisade layer absent, fusoid and arm cells usually absent; midribs usually simple; abaxial bulliform cells present; stomates with parallel-sided subsidiary cells; epidermes usually with bicellular microhairs, sometimes with unicellular microhairs, papillae usually absent, when present, rarely more than 1 per cell. Inflorescencesusually terminal, panicles, spikes, or racemes, usually ebracteate; disarticulation usually below the florets, sometimes below the glumes, at the rachis nodes, or at the inflorescence bases. Spikelets usually bisexual, infrequently unisexual or mixed, usually laterally compressed or not compressed, occasionally dorsally compressed, with 1–30 sexual florets, the distal floret(s) often reduced, infrequently spikelets with 1–2 reduced or staminate basal florets and a single terminal sexual floret. Glumesusually 2, upper glumes sometimes absent, rarely both glumes absent; lemmas without uncinate hairs, awned or not, awns single, basal to apical; paleas usually well-developed, sometimes reduced or absent; lodicules2(3), usually lanceolate and broadly membranous distally, rarely truncate and fleshy, usually not veined or obscurely veined, sometimes distinctly veined, sometimes ciliate; anthers (1, 2)3; ovaries glabrous or sometimes hairy distally, sometimes with an apical appendage; haustorial synergidsabsent; styles usually 2, rarely 1, 3, or 4, bases close together, sometimes fused. Caryopses: hila linear, elliptic, ovate, or punctate; endosperm usually hard, sometimes soft or liquid, with or without lipids, starch grains compound or simple; embryos less than 1/2 the length of the caryopses; epiblasts usually present; scutellar cleft usually absent; mesocotyl internode usually absent; embryonic leaf margins overlapping. x = 5, 6, 7.

The subfamily Poöideae includes approximately 3,300 species, making it the largest subfamily in the Poaceae. Itreaches its greatest diversity in cool temperate and boreal regions, extending across the tropics only in high mountains.

Key to tribes in North America north of Mexico, Pakistan, Somaliland and Somalia (links will be added when keys are posted).