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ASTERACEAE

SUNFLOWER FAMILY

David J. Keil, Family Editor and author, except as specified

Annual to tree
Leaves basal or cauline, alternate to whorled, simple to compound
Inflorescence: 1° inflorescence a head, each resembling a flower, 1–many, generally arrayed in cymes, generally subtended by ± calyx-like involucre; flowers 1–many per head
Flowers bisexual, unisexual, or sterile, ± small, of several types; calyx 0 or modified into pappus of bristles, scales, or awns, which is generally persistent in fruit; corolla radial or bilateral (rarely 0), lobes generally (0)4–5; stamens 4–5, anthers generally fused into cylinder around style, often appendaged at tips, bases, or both, filaments generally free, generally attached to corolla near throat; pistil 1, ovary inferior, 1-chambered, 1-seeded, style 1, branches 2, generally hair-tufted at tip, stigmas 2, generally on inside of style branches
Fruit: achene, cylindric to ovoid, generally deciduous with pappus attached
Genera in family: ± 1300 genera, 21,000 species (largest family of dicots): worldwide. Largest family in CA. Also see tribal key to CA genera: Strother 1997 Madroño 44(1):1–28. See glossary p. 25 for illustrations of general family characteristics.

PETASITES

Perennial from stout rhizome, ± dioecious
Stems erect, appearing before leaves
Leaves: basal, large, long-petioled, blades wide; cauline generally sheathing, scale-like
Inflorescence: heads disciform or weakly radiate, in raceme-like to ± flat-topped clusters; involucre ± cylindric to bell-shaped; main phyllaries in 1 series, equal; receptacle flat, naked
Pistillate flowers 0–few in staminate heads, many in pistillate heads; corollas of 2 kinds, white to pale yellow, sometimes purplish, outer often with short ligules, inner cylindric
Disk flowers staminate, 0–few at center of pistillate heads, many in staminate heads; corollas white to pale yellow, sometimes purplish; anther bases entire or short-sagittate, tips acute; style tips slightly thickened, entire or slightly lobed; pappus reduced
Fruit cylindric, 5–10-ribbed; pappus bristles many
Species in genus: 15 species: North America, Eurasia
Etymology: (Greek: broad-brimmed hat, from large leaves)
Reference: [Cronquist 1978 North America Fl II 10:174–179]

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