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335. Layia Hooker & Arnott ex de Candolle in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 7: 294. 1838.
[For George Tradescant Lay, a naturalist on Beechey’s voyage (1825–1828)]
Bruce G. Baldwin, Susan J. Bainbridge, John L. Strother
Annuals, 2–60(–130) cm. Stems usually ± erect (prostrate in L. chrysanthemoides and L. platyglossa of coastal bluffs). Leaves mostly cauline; proximal opposite, most alternate; sessile; blades ovate, lanceolate, or oblanceolate to linear, sometimes 1–2-pinnatifid, ultimate margins toothed or entire, faces glabrous or hirsute to strigose (distal leaves sometimes stipitate-glandular as well). Heads usually radiate (discoid in L. discoidea), borne singly or in ± corymbiform arrays. Peduncular bracts: pit-glands, tack-glands, and/or spines 0. Involucres ± hemispheric, campanulate, cylindric, ellipsoid, obconic, or urceolate, 2–15+ mm diam. Phyllaries 0 (then outer paleae functioning as phyllaries, in L. discoidea), or 3–27 in 1(–2) series (lanceolate to lance-attenuate or oblanceolate, herbaceous, each usually wholly enveloping a subtended ray ovary, abaxially hirsute to strigose or scabrous, sometimes glandular). Receptacles flat to convex, setulose, paleate (paleae falling, in 1 series, between rays and discs or subtending ± all disc florets, distinct, phyllary-like, more scarious). Ray florets 0 or 3–27, pistillate, fertile; corollas yellow, cream, white, or bicolored. Disc florets 5–120+, bisexual, fertile; corollas yellow, tubes shorter than funnelform throats, lobes 5, deltate (anthers ± dark purple or yellow to brownish; styles glabrous proximal to branches). Ray cypselae obcompressed, clavate (± arcuate to falcate, basal attachments central, apices beakless, faces glabrous or sparsely hairy); pappi 0. Disc cypselae ± clavate (usually ± strigose to sericeous, sometimes glabrous); pappi 0 or of 1–32 elliptic, lance-attenuate, ovate, setiform, or subulate, glabrous, scabrous, or plumose scales or bristles (often each basally villous and/or adaxially woolly). x = 8.
Species 14 (14 in the flora): w North America, nw Mexico.
Layia is evidently most closely related to Lagophylla based on molecular phylogenetic data. Species of Layia with 2n = 14 constitute a clade that has been regarded as exemplary of geographic diversification (speciation) in plants (J. Clausen 1951; B. G. Baldwin, unpubl.). All members of Layia except L. carnosa and L. hieracioides are self-incompatible.
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| 1 |
Disc pappi 0 |
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(2) |
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Disc pappi of 1–32 bristles or scales |
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(7) |
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| 2 (1) |
Plants not glandular; paleae subtending ± all disc florets |
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2 Layia chrysanthemoides (in part) |
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Plants glandular; paleae in 1 (involucre-like) series between ray and disc florets |
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(3) |
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| 3 (2) |
Plants apple- or banana-scented; margins (basal leaves) usually denticulate to serrulate, seldom lobed; ray corollas white to cream |
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1 Layia heterotricha (in part) |
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Plants unscented, or not apple- or banana-scented; margins (basal leaves) lobed; ray corollas white, yellow, or bicolored (proximally yellow, distally whitish) |
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(4) |
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| 4 (3) |
Stems usually purple-streaked; involucres campanulate to hemispheric, subglobose, or ± urceolate |
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(5) |
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Stems usually not purple-streaked; involucres ± hemispheric |
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(6) |
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| 5 (4) |
Involucres campanulate to hemispheric or subglobose; ray florets 6–18, corollas yellow or bicolored (proximally yellow, distally whitish) |
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12 Layia gaillardioides (in part) |
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Involucres ± urceolate; ray florets 13–27 (in 2 series), corollas bicolored |
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5 Layia jonesii (in part) |
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| 6 (4) |
Plants strongly lemon- or acrid-scented; ray corollas white or yellow; anthersyellow or brownish |
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8 Layia pentachaeta (in part) |
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Plants not strongly scented; ray corollas yellow or bicolored (proximally yellow, distally white); anthers ± dark purple (sometimes yellow to brownish in sw California) |
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4 Layia platyglossa (in part) |
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| 7 (1) |
Ray florets 0 |
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10 Layia discoidea |
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Ray florets 3–27 (ray laminae sometimes inconspicuous) |
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(8) |
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| 8 (7) |
Plants not glandular; paleae subtending ± all disc florets |
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(9) |
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Plants glandular; paleae in 1 (involucre-like) series between ray and disc florets |
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(10) |
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| 9 (8) |
Disc pappi of unequal, subulate to setiform scales |
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2 Layia chrysanthemoides (in part) |
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Disc pappi of ± equal, lance-attenuate scales |
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3 Layia fremontii |
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| 10 (8) |
Disc pappi of elliptic, lance-linear, or ovate, non-plumose, non-woolly scales (bases sparsely setose), 0.5–3.5 mm |
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(11) |
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Disc pappi usually of bristles or setiform scales, if scales linear-attenuate to subulate, then proximally plumose and often proximally woolly adaxially, 1–7 mm |
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(13) |
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| 11 (10) |
Ray corollas white; anthers yellow to brownish; ray cypselae sparsely hairy |
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6 Layia leucopappa |
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Ray corollas yellow or bicolored (proximally yellow, distally white); anthers ± dark purple; ray cypselae glabrous or sparsely hairy |
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(12) |
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| 12 (11) |
Stems usually purple-streaked; involucres ± urceolate; ray florets 13–27 (in 2 series); ray cypselae glabrous; pappus scales 0.5–2 mm |
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5 Layia jonesii (in part) |
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Stems not purple-streaked; involucres hemispheric to ± urceolate; ray florets 6–15; ray cypselae glabrous or sparsely hairy; pappusscales 2–3.5 mm |
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7 Layia munzii |
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| 13 (10) |
Plants usually not strongly scented (if not contacted); disc pappus bristles or scales mostly proximally plumose and adaxially woolly, sometimes ± scabrous throughout, if proximally plumose and not woolly, then linear-attenuate to subulate scales |
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(14) |
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Plants usually strongly scented, even without contact (except L. carnosa, fleshy-leaved plants of coastal dunes); disc pappus bristles or scales proximally plumose, seldom woolly adaxially (not linear-attenuate to subulate) |
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(16) |
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| 14 (13) |
Ray corollas usually white (sometimes yellow); disc pappi of 10–15 linearattenuate to subulate scales |
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9 Layia glandulosa |
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Ray corollas yellow or bicolored (proximally yellow, distally white); disc pappi of 14–32 bristles or setiform scales |
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(15) |
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| 15 (14) |
Involucres usually ± hemispheric; phyllary apices often longer than folded bases; ray corollas yellow or bicolored (proximally yellow, distally white); anthers usually ± dark purple (sometimes yellow to brownish in sw California); disc pappus bristles or scales usually scabrous (sometimes proximally plumose and adaxially woolly in sw California) |
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4 Layia platyglossa (in part) |
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Involucres ± ellipsoid to campanulate; phyllary apices usually shorter than folded bases; ray corollas yellow; anthers yellow to brownish; disc pappus bristles orscales proximally plumose and adaxially woolly |
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11 Layia septentrionalis |
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| 16 (13) |
Margins (basal leaves) usually denticulate or serrulate, seldom toothed or lobed;ray corollas white to cream (disc pappi readily falling as units) |
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1 Layia heterotricha (in part) |
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Margins (basal leaves) lobed; ray corollas white, yellow, or bicolored (proximally yellow, distally whitish) |
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(17) |
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| 17 (16) |
Anthers yellow to brownish |
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8 Layia pentachaeta (in part) |
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Anthers ± dark purple |
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(18) |
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| 18 (17) |
Stems not purple-streaked; ray corollas white, laminae 1.5–3.5 mm; ray cypselae sparsely hairy |
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14 Layia carnosa |
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Stems purple-streaked; ray corollas yellow or bicolored (proximally yellow, distally white), laminae 1–18 mm; ray cypselae glabrous |
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(19) |
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| 19 (18) |
Ray corollas yellow or bicolored (proximally yellow, distally whitish), 3.5–18 mm; disc pappi of 15–24 bristles or setiform scales (main stemsascending, not strictly erect) |
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12 Layia gaillardioides (in part) |
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Ray corollas yellow, 1–4 mm; disc pappi of 10–16 bristles or setiform scales (main stems strictly erect) |
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13 Layia hieracioides |
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List of lower taxa
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