Jepson Flora Project: Jepson Interchange    

 
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Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California
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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.

LACTUCA

LETTUCE

G. Ledyard Stebbins

Annual to perennial herb; sap milky
Stems erect, 0.5–1.5+ m
Leaves basal and cauline, alternate, entire to pinnately lobed
Inflorescence: heads ligulate, many, in panicles; involucre cylindric; phyllaries in 2–several series; receptacle naked
Flowers few–many; ligules yellow or cream to blue, readily withering
Fruit flattened, short- or long-beaked; pappus of many bristles, falling separately
Species in genus: ± 100 species: ± worldwide temp
Etymology: (Latin: milky)

Introduced

L. virosa L.

Biennial from taproot, 0.6–2 m
Stems erect, arising from a rosette, glabrous or bristly below
Leaves: basal obovate, toothed or shallowly lobed; cauline many, upper widely clasping, prickly-bristly on midvein
Inflorescence: cyme, compound; heads many, in flower 3–4 cm wide; involucre in fruit 8–12 mm
Flowers 15–20; corolla pale yellow
Fruit many-ribbed, rough; body dark, wing-margined; beak white, ± = body; pappus 8 mm, white
Chromosomes: 2n=18
Ecology: Disturbed, shrubby and wooded slopes
Elevation: < 300 m.
Bioregional distribution: San Francisco Bay Area, Outer South Coast Ranges
Distribution outside California: native to Europe

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bioregional map for LACTUCA%20virosa being generated
 
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Retrieve Jepson Interchange Index to Plant Names entry for Lactuca virosa
Retrieve dichotomous key for Lactuca
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