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-d0_s0" data-properties=""><b>Annuals </b>or biennials, 15–450+ cm;</span> <span class="statement" id="st-d0_s1" data-properties="whole-organism some measurement;whole-organism architecture;whole-organism duration;whole-organism some measurement;whole-organism architecture;whole-organism duration">taprooted.</span> <span class="statement" id="st-d0_s2" data-properties="stem quantity;stem orientation;stem architecture;stem pubescence;stem pubescence"><b>Stems </b>usually 1, usually erect, branched distally or throughout, glabrous or hairy (sometimes hispid to setose).</span> <span class="statement" id="st-d0_s3" data-properties=""><b>Leaves </b>basal and cauline or mostly cauline (at flowering);</span> <span class="statement" id="st-d0_s4" data-properties="leaf position;leaf position;leaf position;leaf architecture;leaf architecture">sessile or petiolate;</span> <span class="statement" id="st-d0_s5" data-properties="blade shape;blade shape;blade shape;blade shape;blade shape;blade shape;margin shape">blades orbiculate, ovate, oblong, or lanceolate to oblanceolate, linear, or filiform, margins entire or denticulate to pinnately lobed (faces glabrous or hairy, often ± setose).</span> <span class="statement" id="st-d0_s6" data-properties="head arrangement;head arrangement;array architecture"><b>Heads </b>borne singly or in corymbiform to paniculiform arrays.</span> <span class="statement" id="st-d0_s7" data-properties="peduncle shape;peduncle architecture"><b>Peduncles </b>not inflated distally, sometimes bracteate.</span> <span class="statement" id="st-d0_s8" data-properties="bractlet quantity;bractlet shape;series quantity"><b>Calyculi </b>of 3–10+, deltate to lanceolate bractlets in 2–3 series (sometimes intergrading with phyllaries).</span> <span class="statement" id="st-d0_s9" data-properties="involucre shape;involucre diameter;involucre diameter"><b>Involucres </b>campanulate to cylindric, 2–5 [–8+] mm diam.</span> <span class="statement" id="st-d0_s10" data-properties="phyllary quantity;phyllary shape;phyllary size;phyllary variability;series quantity;margin texture;apex shape"><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.</span> <span class="statement" id="st-d0_s11" data-properties="receptacle shape;receptacle relief;receptacle pubescence;receptacle architecture"><b>Receptacles </b>flat to convex, pitted, glabrous, epaleate.</span> <span class="statement" id="st-d0_s12" data-properties="floret quantity"><b>Florets </b>6–50+;</span> <span class="statement" id="st-d0_s13" data-properties="corolla coloration;corolla coloration;corolla coloration;corolla coloration;corolla coloration">corollas yellow, bluish, or whitish.</span> <span class="statement" id="st-d0_s14" data-properties="cypsela coloration;cypsela coloration;cypsela coloration;cypsela coloration;body shape;body shape;beak fragility or size;beak shape;rib quantity;face relief;face pubescence"><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;</span> <span class="statement" id="st-d0_s15" data-properties="pappus duration;pappus size;corona architecture or relief;corona some measurement;corona position;corona quantity;corona coloration;corona coloration;corona variability;corona architecture;series quantity;bristle quantity;bristle coloration;bristle variability;bristle architecture;series quantity">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.</span> <span class="statement" id="st-d0_s16" data-properties="bristle architecture;x chromosome quantity">x = 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 Lactuca sativa.</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
|illustration copyright=Flora of North America Association
|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://bibilujan@bitbucket.org/aafc-mbb/fna-fine-grained-xml.git/src/84153f6d59a0a91d69695978a64cee7560374f8e/V19-20-21/V19_347.xml
|tribe=Asteraceae tribe Cichorieae
|genus=Lactuca
|apex shape=obtuse;acute
|array architecture=corymbiform;paniculiform
|beak fragility or size=stout
|beak shape=filiform
|blade shape=lanceolate;oblanceolate linear or filiform
|body shape=compressed;flattened elliptic
|bractlet quantity=3;10
|bractlet shape=deltate;lanceolate
|bristle architecture=simple;barbellulate;nearly smooth
|bristle coloration=white
|bristle quantity=80;120
|bristle variability=equal
|corolla coloration=whitish;bluish;whitish;bluish;yellow
|corona architecture=barbellate;barbellulate
|corona architecture or relief=erose
|corona coloration=fuscous;white
|corona position=subtending
|corona quantity=40;80
|corona some measurement=0.05mm;0.2mm
|corona variability=equal
|cypsela coloration=purplish;blackish
|face pubescence=glabrous
|face relief=rugulose
|floret quantity=6;50
|head arrangement=in corymbiform to paniculiform arrays;singly
|involucre diameter=2mm;5mm
|involucre shape=campanulate;cylindric
|leaf architecture=petiolate;sessile
|leaf position=cauline;cauline;basal
|margin shape=denticulate;pinnately lobed
|margin texture=scarious
|pappus duration=persistent
|pappus size=minute
|peduncle architecture=bracteate
|peduncle shape=inflated
|phyllary quantity=5;13
|phyllary shape=lanceolate;linear
|phyllary size=subequal
|phyllary variability=equal
|receptacle architecture=epaleate
|receptacle pubescence=glabrous
|receptacle relief=pitted
|receptacle shape=flat;convex
|rib quantity=1;9
|series quantity=2;3
|stem architecture=branched
|stem orientation=erect
|stem pubescence=hairy;glabrous
|stem quantity=1
|whole-organism architecture=taprooted;taprooted
|whole-organism duration=biennial;annual
|whole-organism some measurement=15cm;450cm
|x chromosome quantity=9
}}<!--

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