View source for Lactuca

{{Treatment/ID
|accepted_name=Lactuca
|accepted_authority=Linnaeus
|publications={{Treatment/Publication
|title=Sp. Pl.
|place=2: 795. 1753
|year=1753
}}, {{Treatment/Publication
|title=Gen. Pl. ed.
|place=5, 348. 1754
|year=1754
}}
|common_names=Lettuce;laitue
|basionyms=
|synonyms=
|hierarchy=Asteraceae;Asteraceae tribe Cichorieae;Lactuca
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Asteraceae]]</div><div class="higher-taxon"><small>tribe</small>[[Asteraceae tribe Cichorieae]]</div><div class="higher-taxon"><small>genus</small>[[Lactuca]]</div></div>
|etymology=No etymology in protologue; traceable to Latin lac, milk, alluding to the milky sap
|volume=Volume 19
|mention_page=page 216, 258
|treatment_page=page 259
}}<!--

--><span class="statement" id="st-undefined" data-properties=""><b>Annuals </b>or biennials, 15–450+ cm; taprooted. <b>Stems</b> usually 1, usually erect, branched distally or throughout, glabrous or hairy (sometimes hispid to setose). <b>Leaves</b> basal and cauline or mostly cauline (at flowering); sessile or petiolate; blades orbiculate, ovate, oblong, or lanceolate to oblanceolate, linear, or filiform, margins entire or denticulate to pinnately lobed (faces glabrous or hairy, often ± setose). <b>Heads</b> borne singly or in corymbiform to paniculiform arrays. <b>Peduncles</b> not inflated distally, sometimes bracteate. <b>Calyculi</b> of 3–10+, deltate to lanceolate bractlets in 2–3 series (sometimes intergrading with phyllaries). <b>Involucres</b> campanulate to cylindric, 2–5[–8+] mm diam. <b>Phyllaries</b> 5–13+ in ± 2 series (erect or reflexed in fruit), lanceolate to linear, usually subequal to equal, margins sometimes scarious, apices obtuse to acute. <b>Receptacles</b> flat to convex, pitted, glabrous, epaleate. <b>Florets</b> 6–50+; corollas yellow, bluish, or whitish. <b>Cypselae</b> reddish brown, tan, whitish, or purplish to blackish, bodies compressed to flattened, elliptic to oblong, beaks stout (0.1–1 mm, gradually or weakly set off from bodies) or filiform (2–6 mm, sharply set off from bodies), ribs 1–9 on each face, faces often transversely rugulose, usually glabrous; pappi persistent (borne on discs at tips of cypselae or beaks), obscurely double (spp. 1–2), each a minute, erose corona 0.05–0.2 mm subtending 40–80+, white or fuscous, ± equal, barbellate to barbellulate bristles in 1–2 series, or simple (spp. 3–10) of 80–120+, white, ± equal, barbellulate to nearly smooth bristles in 2–3+ series. <b>x</b> = 9.</span><!--

-->{{Treatment/Body
|distribution=North America;Mexico;Central America;Eurasia;Africa.
|discussion=<p>Species ca. 75 (10 in the flora).</p><!--
--><p>The common head and leaf lettuces of home gardens and commerce are derived from <i>Lactuca sativa</i>.</p>
|tables=
|references=
}}<!--

--><div class="treatment-key">
==Key==
<div class="treatment-key-group">
  
{| class="wikitable fna-keytable"
|-id=key-0-1
|1
|Corollas usually bluish, sometimes white, rarely yellow, not or seldom deliquescent; cypselae ± compressed-lanceoloid to compressed-fusiform, beaks 0 or ± stout (gradually set off from bodies of cypselae), 0.1–0.5(–1) mm
|[[#key-0-2| > 2]]
|-id=key-0-1
|1
|Corollas usually yellow, sometimes bluish (or drying bluish) or white, usually deliquescent; cypselae ± flattened, ± elliptic to obovate or oblanceolate, beaks ± filiform (sharply set off from bodies of cypselae), 1–4+ mm
|[[#key-0-3| > 3]]
|-id=key-0-2
|2
|Florets (15–)20–30(–50+); pappi ± fuscous
|[[Lactuca biennis|Lactuca biennis]]
|-id=key-0-2
|2
|Florets 10–15(–25+); pappi white
|[[Lactuca floridana|Lactuca floridana]]
|-id=key-0-3
|3
|Faces of cypselae 1(–3)-nerved
|[[#key-0-4| > 4]]
|-id=key-0-3
|3
|Faces of cypselae (3–)5–9-nerved
|[[#key-0-7| > 7]]
|-id=key-0-4
|4
|Involucres 10–12 mm; cypsela bodies 2.5–3.5 mm
|[[Lactuca canadensis|Lactuca canadensis]]
|-id=key-0-4
|4
|Involucres 12–20 mm; cypsela bodies 4.5–6 mm
|[[#key-0-5| > 5]]
|-id=key-0-5
|5
|Leaves on proximal 1/3–1/2 of each stem, blades spatulate to lance-linear
|[[Lactuca graminifolia|Lactuca graminifolia]]
|-id=key-0-5
|5
|Leaves on proximal (1/3–)1/2–3/4 of each stem, blades ovate or oblanceolate to spatulate
|[[#key-0-6| > 6]]
|-id=key-0-6
|6
|Margins of leaf blades entire or denticulate, seldom prickly; florets 12– 24+
|[[Lactuca hirsuta|Lactuca hirsuta]]
|-id=key-0-6
|6
|Margins of leaf blades ± toothed, ± prickly; florets 20–50+
|[[Lactuca ludoviciana|Lactuca ludoviciana]]
|-id=key-0-7
|7
|Cypselae purplish to blackish, ± elliptic
|[[Lactuca virosa|Lactuca virosa]]
|-id=key-0-7
|7
|Cypselae pale brown to grayish or whitish, ± obovate or ± oblanceolate
|[[#key-0-8| > 8]]
|-id=key-0-8
|8
|Blades of undivided leaves lanceolate to linear or filiform; heads in racemiform or spiciform arrays
|[[Lactuca saligna|Lactuca saligna]]
|-id=key-0-8
|8
|Blades of undivided leaves mostly ± oblong or mostly obovate to orbiculate; heads in corymbiform or paniculiform arrays
|[[#key-0-9| > 9]]
|-id=key-0-9
|9
|Blades of cauline leaves usually ± oblong, sometimes narrowly obovate to lanceolate, midribs usually prickly setose, rarely smooth; phyllaries usually reflexed in fruit
|[[Lactuca serriola|Lactuca serriola]]
|-id=key-0-9
|9
|Blades of cauline leaves ovate to orbiculate, midribs usually smooth, rarely prickly setose; phyllaries usually erect in fruit
|[[Lactuca sativa|Lactuca sativa]]
|}
</div></div><!--

-->{{#Taxon:
name=Lactuca
|author=John L. Strother
|authority=Linnaeus
|rank=genus
|parent rank=tribe
|synonyms=
|basionyms=
|family=Asteraceae
|illustrator=Marjorie C. Leggitt
|distribution=North America;Mexico;Central America;Eurasia;Africa.
|reference=None
|publication title=Sp. Pl.;Gen. Pl. ed.
|publication year=1753;1754
|special status=
|source xml=https://jpend@bitbucket.org/aafc-mbb/fna-data-curation.git/src/f6b125a955440c0872999024f038d74684f65921/coarse_grained_fna_xml/V19-20-21/V19_347.xml
|tribe=Asteraceae tribe Cichorieae
|genus=Lactuca
}}<!--

-->[[Category:Treatment]][[Category:Asteraceae tribe Cichorieae]]