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61. Lactuca Linnaeus, Sp. Pl. 2: 795. 1753.
莴苣属 wo ju shu
Authors: Zhu Shi & Norbert Kilian
Agathyrsus D. Don; Lactucopsis Schultz Bipontinus ex Visiani; Lagedium Soják; Mulgedium Cassini; Phaenixopus Cassini; Pterocypsela C. Shih; Scariola F. W. Schmidt; Steptorhamphus Bunge.
Herbs, perennial or annual, more rarely subshrubs (only Lactuca orientalis in China). Stems usually leafy. Leaves pinnate or undivided. Capitula with 4-30 or more florets. Involucre narrowly cylindric. Phyllaries glabrous or hairy; outer phyllaries gradually longer centripetally, ± imbricate, often ca. 1/2 as long as inner phyllaries or even ± approaching them in length; inner phyllaries usually 3, 5, or 8, ± linear-lanceolate to linear, often of unequal length in fruit. Receptacle naked. Florets some shade of yellow or blue. Achene narrowly or broadly ellipsoid, body subcompressed to compressed, between 2 thicker or wider lateral ribs with 1 to several slender ribs on either side; beak usually present, stout, slender, or filiform. Pappus white or sometimes with a faint yellow tinge, single, of slender scabrid bristles [or double with an additional outer row of minute hairs].
Probably ca. 50-70 species: mostly in C and SW Asia, Europe, North America; 12 species (one endemic, one introduced) in China.
The circumscription of the genus is not yet settled, and species numbers given in the literature therefore vary greatly. The concept of the genus applied here on the basis of molecular and morphological studies by N. Kilian et al. (in prep.) is wider than the one adopted in FRPS (80(1): 233-239. 1997) and includes, as far as China is concerned, the former segregates Mulgedium, Pterocypsela, and Scariola.
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| 1 |
Subshrubs, stems whitish, rigid, and intricately and divaricately branched; stem leaf bases with linear auricles adnately long decurrent on stem; capitula with 4(or 5) florets. |
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8 L. orientalis |
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Annual to perennial herbs, stems not as above; stem leaf bases never adnately decurrent on stem; capitula with usually 8-30 florets |
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(2) |
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| 2 (1) |
Achene body strongly compressed with distinctly winged margin |
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(3) |
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Achene body strongly compressed to subcompressed but margin not winged |
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(6) |
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| 3 (2) |
Inner phyllaries 5(or 6); achene with 3(-5) prominent ribs on either side. |
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4 L. raddeana |
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Inner phyllaries ca. 8; achene with 1(or 2) prominent rib(s) on either side |
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(4) |
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| 4 (3) |
Leaves not clasping or scarcely clasping stem. |
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6 L. indica |
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Middle and upper stem leaves distinctly clasping stem |
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(5) |
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| 5 (4) |
Achene beak stout, 0.1-0.5 mm, apically pale. |
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5 L. triangulata |
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Achene beak filiform, 2-3.5 mm, pale to greenish. |
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7 L. formosana |
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| 6 (2) |
Achene subcompressed, very narrowly ellipsoid, apically attenuate or contracted into a stout 1-2 mm beak |
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(7) |
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Achene compressed, apically contracted into a filiform (2-)4-12 mm beak |
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(8) |
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| 7 (6) |
Lower and middle stem leaves usually pinnately lobed, base usually narrowed and semiamplexicaul; achene with 5-7 prominent ribs on either side between marginal ribs, marginal ribs slightly thicker than other main ribs. |
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9 L. tatarica |
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Lower and middle stem leaves entire or more rarely sinuate-dentate to pinnately lobed, base usually semiamplexicaul to auriculate; achene with 4 or 5 narrow ribs in middle third of either face and with very thick marginal ribs. |
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10 L. sibirica |
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| 8 (6) |
Beak of achene 10-12 mm, base with rodlike appendages; achene body with 1 rib on either side; involucre to 2.3 cm in fruit. |
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1 L. undulata |
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Beak of achene to 5 mm, base without appendages; achene body with 3-9 ribs on either side; involucre to 1.6 cm in fruit |
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(9) |
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| 9 (8) |
Florets blue; achene body with 3-5 ribs on each side |
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(10) |
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Florets yellow; achene body with 5-9 ribs on each side |
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(11) |
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| 10 (9) |
Lower leaves obovate to elliptic, always pinnately lobed with broader segments; capitula ca. 6 mm at anthesis, to 1.3 cm in fruit; achene beak white. |
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2 L. dissecta |
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All leaves linear, margin entire or lower ones pinnately lobed with linear entire segments; capitula 9-10 mm at anthesis, to 1.6 cm in fruit; achene beak greenish. |
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3 L. dolichophylla |
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| 11 (9) |
Stem leaves undivided, abaxially with smooth midrib; phyllaries usually erect in fruit; achene with 5-7 ribs on each surface. |
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11 L. sativa |
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Stem leaves pinnately lobed, abaxially usually with prickly setose midrib; phyllaries usually reflexed in fruit; achene with 7-9 ribs on each surface. |
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12 L. serriola |
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List of lower taxa
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