Habit and leaf form. Herbs. Annual, or perennial; plants with neither basal nor terminal concentrations of leaves. Leaves opposite (often clustered at the nodes); petiolate, or subsessile, or sessile; simple. Leaf blades entire; elliptic, or ovate, or obovate, or linear; pinnately veined. Leaves without stipules. Leaf blade margins entire. Leaf anatomy. Hairs present, or absent.
Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite.
Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in spikes, or in heads. The terminal inflorescence unit cymose. Inflorescences terminal, or axillary; more or less globular or lengthening during flowering to become ovoid or cylindric. Flowers sessile, or subsessile; bracteate; bracteolate. Bracteoles membranous, more or less folded lengthwise. Flowers regular, or somewhat irregular; cyclic. Free hypanthium absent. Hypogynous disk absent. Perianth sepaline; 5. Calyx present; 5; more or less polysepalous; hairy (often woolly-hairy outside), or glabrous; regular, or unequal but not bilabiate (the outer 3 larger than the inner 2); white, or pink, or red (tinged), or green (in centre); persistent; with the median member posterior. Sepals oblong. Corolla absent. Androecial members definite in number. Androecium 5. Androecial members all equal, or markedly unequal (by misinterpretation); coherent; 1 - adelphous (the filaments connate into a 5-toothed staminal tube; teeth entire or deeply lobed); 1 -whorled. Androecium exclusively of fertile stamens (the true androecium sometimes alternating with tooth-like ‘pseudostaminodes’). Stamens 5; oppositisepalous. Anthers dehiscing via longitudinal slits; introrse; unilocular. Pollen shed as single grains. Gynoecium 2–3 carpelled. The pistil 1 celled. Gynoecium syncarpous; synstylovarious to eu-syncarpous (depending on interpretation of stigmatic branching); superior. Ovary unilocular; 1 locular. Gynoecium stylate. Styles 1 (short or filiform). Stigmas 1; 2 - lobed. Placentation basal. Ovules in the single cavity 1; pendulous; non-arillate; campylotropous.
Fruit and seed features. Fruit non-fleshy; indehiscent; a utricle, thin-walled, membranous, irregularly rupturing, compressed. Seeds compressed-ovoid; non-endospermic (strictly speaking). Perisperm present (abundant, mealy). Embryo well differentiated. Cotyledons 2. Embryo curved. Testa smooth (usually shiny).
Special features. Perianth (calyx) woolly outside, or glabrous outside.
Additional characters Stigmas the stigmatic area linear.