LACTUCA SALIGNA (ASTERACEAE), A LETTUCE NEW FOR TEXAS

5 Pages·1998·2.1 MB·English

by  Robert J O'kennon

LACTUCASALIGNA (ASTERACEAE),
ALETTUCENEWFORTEXAS
ROBERT].O'KENNON
BotanicalResearchInstituteofTexas
509PecanStreet
FortWorth, TX76102-4060, U.S.A., [email protected]
GEORGEM.DIGGS,JR.
DepartmentofBiology
AustinCollege
Sherman, TX75090U.S.A.
andBotanicalResearchInstituteofTexas,[email protected]
BARNEYL.LIPSCOMB
BotanicalResearchInstituteofTexas
509PecanStreet
FortWorth, TX76102-4060, U.S.A.,[email protected]
lactucasalignaL.,willow-leatlettuce,isaEuropeannative(Ferakova1976)
naturalizedinavarietyoflocalitiesintheUnitedStates. Itisusuallyde-
scribedasaweedinhabitingroadsides,disturbedplaces,andwasteareas.
ThespeciesiswidelyknownfromtheeasternU.S.,withlocalitiesreported
fromneartheeastcoast(NorthCarolina,SouthCarolina,Virginia)west
toArkansas,Michigan,Missouri,Ohio,Tennessee,andWestVirginia(Robinson
& Fernald 1908; Britton & Brown 1913; Fernald 1950; Gleason 1952;
Gleason&Cronquist1963, 1991;Steyermark1963;Radfordetal. 1968;
Strausbaugh&Core 1978;Cronquist1980;Smith 1988).Itsspreadhas
apparentlyoccurredmainlyduringthiscenturybecauseitwasreportedby
neitherWatsonandCoulter(1889),BrittonandBrown(1898),norSmall
(1903, 1913, 1933).Further,StrausbaughandCore(1978)indicatedthat
thespecies"...wasnotreportedbyMillspaughIforWestVirginia]in1913,
whichmaybeanindicationthatithasspreadwidelysincethattime."It
was,however,reportedearlyinthecenturyforOhiobyRobinsonandFernald
(1908).A relativelylatespread to thewestissupportedbySteyermark's
(1963)statementthatthespecieswasfirstknownfromMissouriin 1932.
InadditiontotheeasternUnitedStates,Lactucasalignahas—beenreported
fromtheGreatPlains(Iowa,Kansas,Nebraska,SouthDakota GreatPlains
FloraAssociation 1977;Barkley1986)andCalifornia(Stebbins 1993). It
SiDA18(2):615-619. 1998
616 SiDA18(2)
Fu;. 1.Habirol^Lactucasaligiia(Biirton&Brown1913).
isalsoknownFromOklahoma(Taylor&Taylor1994),withformaruppiana
(Wallr.)Beck[entire-leavedform]havingbeenfirstreportedfromthatstate
in 1972(McGrath&Weedon1974).Infact,Lactucasalignaisknownfrom
BryanCounty,Oklahoma,justnorthoftheRedRiverborderwithTexas
t{Jh.eTsapyelcoires2h9a7s40no,t2b8eeAnupgre1v9io8u0s,lyBRreIpTo)r.teHdofwreovmerT,exadess(pCiotreretlhlis&prJooxhinmsittoyn,
1970;Stanford 1976;Hatchetal. 1990;Jonesetal. 1997). &
AspartofthecollectingeffortfortheforthcomingShinners Mahler's
IllustratedFloraofNorthCentralTexas(Diggsetal.),acollectionmadein
1998inFortWorth(TarrantCounty) isapparendythefirstdocumented
occurrenceofthisspeciesforTexas.
WorVtohu,ch2e1rAspuegci1m9e9n8:,TOE'XKeArSu.ioTHar/r4a2n5t2C(o.B:RIwTe)e.dy'areainlandscape,301Crcsrwood,Fort
Atthecollectionlocalityasinglelargeindividualwasobservedasalandscape
weed.Thisplantwasnearlytwometerstallandmorethanameterwide.
OtherpopulationshavenotbeenfoundinNorthCentralTexas,anditis
unclearwhetherthespecieswillbecomemorewidelyestablished. How-
ever,giventhatthespeciesisknownjustnorthoftheRedRiverandthatin
someareasoftheGreatPlainsitisratherfrequent(GreatPlainsFloraAs-
sociation 1977;TedBarkley,pers. comm.), itwouldnotbesurprisingif
O'Kennonetal.,LactucasalignainTexas 617
LactucasalignawerealreadywidespreadbutunnoticedinthestateofTexas.
Lactucasalignacanberecognizedbythefollowingdescription(fromoriginal
observationsandfromRadfordetal. 1968;Ferakova1976;Barkley1986;
Stebbins 1993):Taprootedherbaceousannual(orrarelybiennial?)0.3-l(-
m
2) tall;latexwhite;stemserect,branched,usuallyglabrousorwithre-
motebristles;caulineleaveslineartolinear-lanceolate,entiretopinnatified
with l-2(-3)pairsofnarrow,sometimesslightlytoothedlobes,withsag-
ittate-claspingbase;midribofleafwhite,glabrousorwithremotebristles
abaxially;inflorescencesspike-likepanicleswithnumerousheads;involu-
cres 10-18mmhighinfruit;corollasyellow(withbluishorpurplishon
theabaxialside),dryingblue;ligules4.5-5mmlong;bodyofachenes3-
3.6mmlong,ca.1mmwide,with5-9nervesoneachface;beakofachenes
filiform,usually1.5-3timesaslongasachenebody;pappuswhite,thebristles
ca.4mmlong;In = 18;floweringJul-frost.Theaccompanyingillustra-
tion(Fig. 1)isreprintedfromBrittonandBrown(1913).
WhiletheTarrantCountyindividualhas mostlypinnatifidlowerand
middleleavesandentireupperleaves,leavesinthisspeciescanvarygreatly.
According toBarkley(1986), "Three phases ofL, saligna based on leaf
morphologyoccurthroughoutitsrange.Thephasewithallleaveslinear
andentire,referredtobyFernaldasf [forma}rnppiana(Wallr.)G.Beck,
willoftenoccurinthesamepopulationwiththephasethathasallleaves
pinnatifid.Thephasewithlowercaulineleavespinnatifidanduppercauline
leaveslinearandentiremaybefoundwithoneorbothoftheotherphases."
ThesixspeciesofLactucaoccurringintheeasterntwo-thirdsofTexas
(excludingthetwospecieslimitedtotheTrans-Pecos)canbedistinguished
usingthefollowingkeymodifiedfromthoseinRadfordetal.(1968),Correll
andJohnston(1970),Barkley(1986),andStebbins(1993):
1.BmeamkloofnagchOeRnesab(sceonntn;eccotrionlglaascbhleuneeobrowdhyitaen;dbpoadpypuosf)ascthoeutn,es0.45--5l(m~2m)
long L.floridana(L.)Gaertn.
1.Beakofachenesthread-like,2-10mmlong;corollasusuallyyellow(rarely
creamtopinkorpalelavender);bodyofachenesofvariouslengths.
2.Beakofachenesequaltoorconspicuouslylongerthanbodyofachenes;
bodyofachenesca. 1 mmwide,ca. 1/3asthickaswide,5-to9-
nervedoneachface;plantsannuals(orrarelybiennials)withtap-
root;latexwhite.
3.Leaveslineartolinear-lanceolate,0.3-5cmwide,withnarrowlobes
ORlobesabsent(exceptforbasallobes);marginsofleavesorleaf
lobesentireorremotelyprickly-toothed;bodyofacheneswith-
outconspicuousbristlesatbaseofbeak;flowers8-15perhead;
abaxialmidribofleavesandlowerstemsglabrousorremotelybristly•••L-salignaL.
3.Leaveslanceolatetoovate,oblong-elliptic,orobovate,1-10(-15+)
cmwide,withbroadlobes;marginsofleavesorleaflobesusually
conspicuouslyprickly-toothed;bodyofacheneswithconspicu-
ousbristlesatbaseofbeak;flowers14-25perhead;abaxialmid-
ribofleavesandlowerstemsusuallywithstiffbristles L.serriolaL.
618 SiDA18(2)
2. Beakofachenesequaltoorshorterthanbodyotachenes;bodyof
achcnes1.6-3mmwide,veryflat,1-to3-nefvedoneachface;plants
biennialswithabundant,lulted,branchingroots;latexbrownish.
4.Corollasverypaleyellowtocream,pink,orpalekivender;lower
leavesusuallypinnatelylobcd;uppermidstemleavesusuallywithout
aclaspingbase;bodyofachenes2-2.5timesaslongaswide;in-
frequentinsandywoLo.dshirinsuetaastMeurhnlT.exvaasnalbiflora(Terr.&A.Gray)Shinners
4.Corollasusuallyyellow;lowerleavespinnatelylobedORnotso;
bodyofachenes1.5—2timesaslongaswide:widespreadinvari-
oussoilsin Texas.
5.Bodyolachenes4.5-5mmlong,theachenesincludingbeak
722-1m0mmmlolnogngi;npfarpuiptu;subprpiesrdeslea7f-1bl0admemsplionnnga;tienlvyolluocbreeds,1t3h-e
marginsconspicuouslyprickly-toothed L.ludovlciana(Nutt.)Riddell
5.Bodyolachenes3.5—4.5mmlong,theachenesincludingbeak
4.5-6.5nunlong;pappusbristles5-7mmlong;involucres
10-15lumlonginfruit;upperleafbladesusuallynotlobed,
themarginsentiretotoothedburusuallynotprickly-toothed
L.canadensisL.
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