Layia
in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 7: 294. 1838.
| Taxon | Illustrator ⠉ | |
|---|---|---|
 | Lagophylla ramosissima Layia platyglossa Layia glandulosa | Barbara Alongi Yevonn Wilson-Ramsey Yevonn Wilson-Ramsey |
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.
Distribution
w North America, nw Mexico
Discussion
Species 14 (14 in the flora).
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.
Selected References
None.
Lower Taxa
Key
| 1 | Disc pappi 0 | > 2 |
| 1 | Disc pappi of 1–32 bristles or scales | > 7 |
| 2 | Plants not glandular; paleae subtending ± all disc florets | Layia chrysanthemoides |
| 2 | Plants glandular; paleae in 1 (involucre-like) series between ray and disc florets | > 3 |
| 3 | Plants apple- or banana-scented; margins (basal leaves) usually denticulate to serrulate, seldom lobed; ray corollas white to cream | Layia heterotricha |
| 3 | Plants unscented, or not apple- or banana-scented; margins (basal leaves) lobed; ray corollas white, yellow, or bicolored (proximally yellow, distally whitish) | > 4 |
| 4 | Stems usually purple-streaked; involucres campanulate to hemispheric, subglobose, or ± urceolate | > 5 |
| 4 | Stems usually not purple-streaked; involucres ± hemispheric | > 6 |
| 5 | Involucres campanulate to hemispheric or subglobose; ray florets 6–18, corollas yellow or bicolored (proximally yellow, distally whitish) | Layia gaillardioides |
| 5 | Involucres ± urceolate; ray florets 13–27 (in 2 series), corollas bicolored | Layia jonesii |
| 6 | Plants strongly lemon- or acrid-scented; ray corollas white or yellow; anthersyellow or brownish | Layia pentachaeta |
| 6 | Plants not strongly scented; ray corollas yellow or bicolored (proximally yellow, distally white); anthers ± dark purple (sometimes yellow to brownish in sw California) | Layia platyglossa |
| 7 | Ray florets 0 | Layia discoidea |
| 7 | Ray florets 3–27 (ray laminae sometimes inconspicuous) | > 8 |
| 8 | Plants not glandular; paleae subtending ± all disc florets | > 9 |
| 8 | Plants glandular; paleae in 1 (involucre-like) series between ray and disc florets | > 10 |
| 9 | Disc pappi of unequal, subulate to setiform scales | Layia chrysanthemoides |
| 9 | Disc pappi of ± equal, lance-attenuate scales | Layia fremontii |
| 10 | Disc pappi of elliptic, lance-linear, or ovate, non-plumose, non-woolly scales (bases sparsely setose), 0.5–3.5 mm | > 11 |
| 10 | 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 | > 13 |
| 11 | Ray corollas white; anthers yellow to brownish; ray cypselae sparsely hairy | Layia leucopappa |
| 11 | Ray corollas yellow or bicolored (proximally yellow, distally white); anthers ± dark purple; ray cypselae glabrous or sparsely hairy | > 12 |
| 12 | Stems usually purple-streaked; involucres ± urceolate; ray florets 13–27 (in 2 series); ray cypselae glabrous; pappus scales 0.5–2 mm | Layia jonesii |
| 12 | Stems not purple-streaked; involucres hemispheric to ± urceolate; ray florets 6–15; ray cypselae glabrous or sparsely hairy; pappusscales 2–3.5 mm | Layia munzii |
| 13 | 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 | > 14 |
| 13 | 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) | > 16 |
| 14 | Ray corollas usually white (sometimes yellow); disc pappi of 10–15 linearattenuate to subulate scales | Layia glandulosa |
| 14 | Ray corollas yellow or bicolored (proximally yellow, distally white); disc pappi of 14–32 bristles or setiform scales | > 15 |
| 15 | 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) | Layia platyglossa |
| 15 | 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 | Layia septentrionalis |
| 16 | Margins (basal leaves) usually denticulate or serrulate, seldom toothed or lobed;ray corollas white to cream (disc pappi readily falling as units) | Layia heterotricha |
| 16 | Margins (basal leaves) lobed; ray corollas white, yellow, or bicolored (proximally yellow, distally whitish) | > 17 |
| 17 | Anthers yellow to brownish | Layia pentachaeta |
| 17 | Anthers ± dark purple | > 18 |
| 18 | Stems not purple-streaked; ray corollas white, laminae 1.5–3.5 mm; ray cypselae sparsely hairy | Layia carnosa |
| 18 | Stems purple-streaked; ray corollas yellow or bicolored (proximally yellow, distally white), laminae 1–18 mm; ray cypselae glabrous | > 19 |
| 19 | 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) | Layia gaillardioides |
| 19 | Ray corollas yellow, 1–4 mm; disc pappi of 10–16 bristles or setiform scales (main stems strictly erect) | Layia hieracioides |