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

Layia carnosa, Layia chrysanthemoides, Layia discoidea, Layia fremontii, Layia gaillardioides, Layia glandulosa, Layia heterotricha, Layia hieracioides, Layia jonesii, Layia leucopappa, Layia munzii, Layia pentachaeta, Layia platyglossa, Layia septentrionalis

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