wouldgladlypublishyourobservations，anditisagreatpitytheyshouldbelost。IfyoulikeIwouldsendyourpapertoeitherquarterwithanote。Inthiscaseyoumustgiveatitle，andyourname，andperhapsitwouldbewelltopremiseyourremarkswithalineofreferencetomypaperstatingthatyouhadobservedindependentlyandmorefully。
Ihavereadmyownpaperoverafteranintervalofseveralyears，andamamusedatthecautionwithwhichIputthecasethatthefinalendwasforcrossingdistinctindividuals，ofwhichIwasthenasfullyconvincedasnow，butIknewthatthedoctrinewouldshockallbotanists。Nowtheopinionisbecomingfamiliar。
Toseepenetrationofpollen—tubesisnotdifficult，butinmostcasesrequiressomepracticewithdissectingunderaone—tenthofaninchfocaldistancesinglelens;andjustatfirstthiswillseemtoyouextremelydifficult。
Whatacapitalobserveryouare——afirst—rateNaturalisthasbeensacrificed，orpartlysacrificedtoPubliclife。
Believeme，yoursverysincerely，CH。DARWIN。
P。S。——IfyoucomeacrossanylargeSalvia，lookatit——thecontrivanceisadmirable。ItwenttomyhearttotellamanwhocamehereafewweeksagowithsplendiddrawingsandMS。onSalvia，thattheworkhadbeenalldoneinGermany。（Dr。W。Ogle，theobserverofthefertilisationofSalviaherealludedto，publishedhisresultsinthe’Pop。ScienceReview，’1869。HerefersbothgracefullyandgratefullytohisrelationshipwithmyfatherintheintroductiontohistranslationofKerner’s’FlowersandtheirUnbiddenGuests。’）
[Thefollowingextractisfromaletter，November26th，1868，toSirThomasFarrer，writtenasIlearnfromhim，"inanswertoarequestforsomeadviceastothebestmodesofobservation。"
"Inmyopinionthebestplanistogoonworkingandmakingcopiousnotes，withoutmuchthoughtofpublication，andtheniftheresultsturnoutstrikingpublishthem。Itismyimpression，butIdonotfeelsurethatI
amright，thatthebestandmostnovelplanwouldbe，insteadofdescribingthemeansoffertilisationinparticularplants，toinvestigatethepartwhichcertainstructuresplaywithallplantsorthroughoutcertainorders;
forinstance，thebrushofhairsonthestyle，orthediadelphousconditionofthestamens，intheLeguminosae，orthehairswithinthecorolla，etc。
etc。Lookingtoyournote，Ithinkthatthisisperhapstheplanwhichyousuggest。
"ItiswelltorememberthatNaturalistsvalueobservationsfarmorethanreasoning;thereforeyourconclusionsshouldbeasoftenaspossiblefortifiedbynoticinghowinsectsactuallydothework。"
In1869，SirThomasFarrercorrespondedwithmyfatheronthefertilisationofPassifloraandofTacsonia。Hehasgivenmehisimpressionsofthecorrespondence:——
"Ihadsuggestedthattheelaborateseriesofchevaux—de—frise，bywhichthenectaryofthecommonPassifloraisguarded，werespeciallycalculatedtoprotecttheflowerfromthestiff—beakedhummingbirdswhichwouldnotfertiliseit，andtofacilitatetheaccessofthelittleproboscisofthehumblebee，whichwoulddoso;whilst，ontheotherhand，thelongpendenttubeandflexiblevalve—likecoronawhichretainsthenectarofTacsoniawouldshutoutthebee，whichwouldnot，andadmitthehummingbirdwhichwould，fertilisethatflower。Thesuggestionisverypossiblyworthless，andcouldonlybeverifiedorrefutedbyexaminationofflowersinthecountrieswheretheygrownaturally……Whatinterestedmewastoseethatonthisasonalmostanyotherpointofdetailedobservation，Mr。Darwincouldalwayssay，’Yes;butatonetimeImadesomeobservationsmyselfonthisparticularpoint;andIthinkyouwillfind，etc。etc。’ThatheshouldafteryearsofintervalrememberthathehadnoticedthepeculiarstructuretowhichIwasreferringinthePassifloraprincepsstruckmeatthetimeasveryremarkable。"
Withregardtothespreadofabeliefintheadaptationofflowersforcross—fertilisation，myfatherwrotetoMr。BenthamApril22，1868:
"MostofthecriticismswhichIsometimesmeetwithinFrenchworksagainstthefrequencyofcrossing，Iamcertainaretheresultofmereignorance。
Ihaveneverhithertofoundtheruletofailthatwhenanauthordescribesthestructureofaflowerasspeciallyadaptedforself—fertilisation，itisreallyadaptedforcrossing。TheFumariaceaeofferagoodinstanceofthis，andTreviranusthrewthisorderinmyteeth;butinCorydalis，Hildebrandshowshowutterlyfalsetheideaofself—fertilisationis。Thisauthor’spaperonSalviaisreallyworthreading，andIhaveobservedsomespecies，andknowthatheisaccurate。"
ThenextletterreferstoProfessorHildebrand’spaperonCorydalis，publishedinthe’Proc。Internat。Hort。Congress，’London，1866，andinPringsheim’s’Jahrbucher，’volumev。ThememoironSalviaalludedtoiscontainedinthepreviousvolumeofthesameJournal:]
CHARLESDARWINTOF。HILDEBRAND。（ProfessorofBotanyatFreiburg。）
Down，May16[1866]。
MydearSir，ThestateofmyhealthpreventsmyattendingtheHort。Congress;butI
forwardedyesterdayyourpapertothesecretary，andiftheyarenotoverwhelmedwithpapers，yourswillbegladlyreceived。IhavemademanyobservationsontheFumariaceae，andconvincedmyselfthattheywereadaptedforinsectagency;butIneverobservedanythingnearlysocuriousasyourmostinterestingfacts。IhopeyouwillrepeatyourexperimentsontheCorydalisonalargerscale，andespeciallyonseveraldistinctplants;
foryourplantmighthavebeenindividuallypeculiar，likecertainindividualplantsofLobelia，etc。，describedbyGartner，andofPassifloraandOrchidsdescribedbyMr。Scott……
Sincewritingtoyoubefore，IhavereadyouradmirablememoironSalvia，andithasinterestedmealmostasmuchaswhenIfirstinvestigatedthestructureofOrchids。Yourpaperillustratesseveralpointsinmy’OriginofSpecies，’especiallythetransitionoforgans。Knowingonlytwoorthreespeciesinthegenus，Ihadoftenmarvelledhowonecelloftheanthercouldhavebeentransformedintothemovableplateorspoon;andhowwellyoushowthegradations;butIamsurprisedthatyoudidnotmorestronglyinsistonthispoint。
Ishallbestillmoresurprisedifyoudonotultimatelycometothesamebeliefwithme，asshownbysomanybeautifulcontrivances，thatallplantsrequire，fromsomeunknowncause，tobeoccasionallyfertilizedbypollenfromadistinctindividual。Withsincererespect，believeme，mydearSir，Yoursveryfaithfully，CH。DARWIN。
[ThefollowingletterreferstothelateHermannMuller’s’BefruchtungderBlumen，’byfarthemostvaluableofthemassofliteratureoriginatinginthe’FertilisationofOrchids。’AnEnglishtranslation，byProf。D’ArcyThompsonwaspublishedin1883。Myfather’s"PrefatoryNotice"tothisworkisdatedFebruary6，1882，andisthereforealmostthelastofhiswritings:]
CHARLESDARWINTOH。MULLER。
Down，May5，1873。
MydearSir，OwingtoallsortsofinterruptionsandtomyreadingGermansoslowly，I
havereadonlytopage88ofyourbook;butImusthavethepleasureoftellingyouhowveryvaluableaworkitappearstome。Independentlyofthemanyoriginalobservations，whichofcourseformthemostimportantpart，theworkwillbeofthehighestuseasameansofreferencetoallthathasbeendoneonthesubject。Iamfairlyastonishedatthenumberofspeciesofinsects，thevisitsofwhichtodifferentflowersyouhaverecorded。Youmusthaveworkedinthemostindefatigablemanner。Abouthalfayearagotheeditorof’Nature’suggestedthatitwouldbeagrandundertakingifanumberofnaturalistsweretodowhatyouhavealreadydoneonsolargeascalewithrespecttothevisitsofinsects。Ihavebeenparticularlygladtoreadyourhistoricalsketch，forIhadneverbeforeseenallthereferencesputtogether。IhavesometimesfearedthatIwasinerrorwhenIsaidthatC。K。Sprengeldidnotfullyperceivethatcross—fertilisationwasthefinalendofthestructureofflowers;butnowthisfearisrelieved，anditisagreatsatisfactiontometobelievethatIhaveaidedinmakinghisexcellentbookmoregenerallyknown。NothinghassurprisedmemorethantoseeinyourhistoricalsketchhowmuchI
myselfhavedoneonthesubject，asitneverbeforeoccurredtometothinkofallmypapersasawhole。ButIdonotdoubtthatyourgenerousappreciationofthelaboursofothershasledyoutoover—estimatewhatI
havedone。Withverysincerethanksandrespect，believeme，Yoursfaithfully，CHARLESDARWIN。
P。S。——Ihavementionedyourbooktoalmosteveryonewho，asfarasIknow，caresforthesubjectinEngland;andIhaveorderedacopytobesendtoourRoyalSociety。
[Thenextletter，toDr。Behrens，referstothesamesubjectasthelast:]
CHARLESDARWINTOW。BEHRENS。
Down，August29[1878]。
DearSir，Iamverymuchobligedtoyouforhavingsentmeyour’GeschichtederBestaubungs—Theorie’（Progr。derK。GewerbschulezuElberfeld，1877，1878。），andwhichhasinterestedmemuch。Ithasputsomethingsinanewlight，andhastoldmeotherthingswhichIdidnotknow。IheartilyagreewithyouinyourhighappreciationofpooroldC。Sprengel’swork;andoneregretsbitterlythathedidnotlivetoseehislaboursthusvalued。ItrejoicesmealsotonoticehowhighlyyouappreciateH。Muller，whohasalwaysseemedtomeanadmirableobserverandreasoner。IamatpresentendeavouringtopersuadeanEnglishpublishertobringoutatranslationofhis’Befruchtung。’
Lastly，permitmetothankyouforyourverygenerousremarksonmyworks。
ByplacingwhatIhavebeenabletodoonthissubjectinsystematicorder，youhavemademethinkmorehighlyofmyownworkthanIeverdidbefore！
Nevertheless，Ifearthatyouhavedonememorethanjustice。
Iremain，dearSir，yoursfaithfullyandobliged，CHARLESDARWIN。
[TheletterwhichfollowswascalledforthbyDr。Gray’sarticlein’Nature，’towhichreferencehasalreadybeenmade，andwhichappearedJune4，1874:]
CHARLESDARWINTOASAGRAY。
Down，June3[1874]。
MydearGray，Iwasrejoicedtoseeyourhand—writingagaininyournoteofthe4th，ofwhichmoreanon。Iwasastonishedtoseeannouncedaboutaweekagothatyouweregoingtowritein’Nature’anarticleonme，andthismorningI
receivedanadvancecopy。Itisthegrandestthingeverwrittenaboutme，especiallyascomingfromamanlikeyourself。Ithasdeeplypleasedme，particularlysomeofyoursideremarks。ItisawonderfulthingtometolivetoseemynamecoupledinanyfashionwiththatofRobertBrown。Butyouareaboldman，forIamsurethatyouwillbesneeredatbynotafewbotanists。Ihaveneverbeensohonouredbefore，andIhopeitwilldomegoodandmakemetrytobeascarefulaspossible;andgoodheavens，howdifficultaccuracyis！Ifeelaveryproudman，butIhopethiswon’tlast……
[FritzMullerhasobservedthattheflowersofHedychiumaresoarrangedthatthepollenisremovedbythewingsofhoveringbutterflies。Myfather’spredictionofthisobservationisgiveninthefollowingletter:]
CHARLESDARWINTOH。MULLER。
Down，August7，1876……Iwasmuchinterestedbyyourbrother’sarticleonHedychium;abouttwoyearsagoIwassoconvincedthattheflowerswerefertilizedbythetipsofthewingsoflargemoths，thatIwrotetoIndiatoaskamantoobservetheflowersandcatchthemothsatwork，andhesentme20to30Sphinx—
moths，butsobadlypackedthattheyallarrivedinfragments;andIcouldmakeoutnothing……
Yourssincerely，CH。DARWIN。
[Thefollowingextractfromaletter（February25，1864），toDr。Grayreferstoanotherpredictionfulfilled:——
"Ihaveofcourseseennoone，andexceptgooddearHooker，Ihearfromnoone。He，likeagoodandtruefriend，thoughsooverworked，oftenwritestome。
"Ihavehadoneletterwhichhasinterestedmegreatly，withapaper，whichwillappearintheLinneanJournal，byDr。CrugerofTrinidad，whichshowsthatIamallrightaboutCatasetum，eventothespotwherethepolliniaadheretothebees，whichvisittheflower，asIsaid，tognawthelabellum。Cruger’saccountofCoryanthesandtheuseofthebucket—likelabellumfullofwaterbeatseverything:ISUSPECTthatthebeesbeingwellwettedflattenstheirhairs，andallowsthevisciddisctoadhere。"]
CHARLESDARWINTOTHEMARQUISDESAPORTA。
Down，December24，1877。
MydearSir，Ithankyousincerelyforyourlongandmostinterestingletter，whichI
shouldhaveansweredsoonerhaditnotbeendelayedinLondon。IhadnotheardbeforethatIwastobeproposedasaCorrespondingMemberoftheInstitute。LivingsoretiredalifeasIdo，suchhonoursaffectmeverylittle，andIcansaywithentiretruththatyourkindexpressionofsympathyhasgivenandwillgivememuchmorepleasurethantheelectionitself，shouldIbeelected。
Yourideathatdicotyledonousplantswerenotdevelopedinforceuntilsuckinginsectshadbeenevolvedseemstomeasplendidone。Iamsurprisedthattheideaneveroccurredtome，butthisisalwaysthecasewhenonefirsthearsanewandsimpleexplanationofsomemysteriousphenomenon……Iformerlyshowedthatwemightfairlyassumethatthebeautyofflowers，theirsweetodourandcopiousnectar，maybeattributedtotheexistenceofflower—hauntinginsects，butyouridea，whichIhopeyouwillpublish，goesmuchfurtherandismuchmoreimportant。WithrespecttothegreatdevelopmentofmammifersinthelaterGeologicalperiodsfollowingfromthedevelopmentofdicotyledons，Ithinkitoughttobeprovedthatsuchanimalsasdeer，cows，horses，etc。couldnotflourishiffedexclusivelyonthegramineaeandotheranemophilousmonocotyledons;andI
donotsupposethatanyevidenceonthisheadexists。
Yoursuggestionofstudyingthemanneroffertilisationofthesurvivingmembersofthemostancientformsofthedicotyledonsisaverygoodone，andIhopethatyouwillkeepitinmindyourself，forIhaveturnedmyattentiontoothersubjects。DelpinoIthinksaysthatMagnoliaisfertilisedbyinsectswhichgnawthepetals，andIshouldnotbesurprisedifthesamefactholdsgoodwithNymphaea。WheneverIhavelookedattheflowersoftheselatterplantsIhavefeltinclinedtoadmittheviewthatpetalsaremodifiedstamens，andnotmodifiedleaves;thoughPoinsettiaseemstoshowthattrueleavesmightbeconvertedintocolouredpetals。I
grievetosaythatIhaveneverbeenproperlygroundedinBotanyandhavestudiedonlyspecialpoints——thereforeIcannotpretendtoexpressanyopiniononyourremarksontheoriginoftheflowersoftheConiferae，Gnetaceae，etc。;butIhavebeendelightedwithwhatyousayontheconversionofamonoeciousspeciesintoahermaphroditeonebythecondensationsoftheverticilsonabranchbearingfemaleflowersnearthesummit，andmaleflowersbelow。
IexpectHookertocomeherebeforelong，andIwillthenshowhimyourdrawing，andifhemakesanyimportantremarksIwillcommunicatewithyou。
HeisverybusyatpresentinclearingoffarrearsafterhisAmericanExpedition，sothatIdonotliketotroublehim，evenwiththebriefestnote。IamatpresentworkingwithmysonatsomePhysiologicalsubjects，andwearearrivingatverycuriousresults，buttheyarenotasyetsufficientlycertaintobeworthcommunicatingtoyou……
[In1877asecondeditionofthe’FertilisationofOrchids’waspublished，thefirsteditionhavingbeenforsometimeoutofprint。Theneweditionwasremodelledandalmostre—written，andalargeamountofnewmatteradded，muchofwhichtheauthorowedtohisfriendFritzMuller。
WithregardtothiseditionhewrotetoDr。Gray:——
"IdonotsupposeIshalleveragaintouchthebook。AftermuchdoubtI
haveresolvedtoactinthiswaywithallmybooksforthefuture;thatistocorrectthemonceandnevertouchthemagain，soastousethesmallquantityofworkleftinmefornewmatter。"
Hemayhavefeltadiminutionofhispowersofreviewinglargebodiesoffacts，suchaswouldbeneededinthepreparationofneweditions，buthispowersofobservationwerecertainlynotdiminished。HewrotetoMr。DyeronJuly14，1878:]
MydearDyer，ThaliadealbatawassentmefromKew:ithasfloweredandafterlookingcasuallyattheflowers，theyhavedrivenmealmostmad，andIhaveworkedatthemforaweek:itisasgrandacaseasthatofCatasetum。
Pistilvigorouslymotile（sothatwholeflowershakeswhenpistilsuddenlycoilsup）;whenexcitedbyatouchthetwofilaments[are]producedlaterallyandtransverselyacrosstheflower（justoverthenectar）fromoneofthepetalsormodifiedstamens。ItissplendidtowatchthephenomenonunderaweakpowerwhenabristleisinsertedintoaYOUNG
flowerwhichnoinsecthasvisited。AsfarasIknowStylidiumisthesolecaseofsensitivepistilandhereitisthepistilstamens。InThalia（HildebrandhasdescribedanexplosivearrangementinsomeoftheMaranteae——thetribetowhichThaliabelongs。）cross—fertilisationisensuredbythewonderfulmovement，ifbeesvisitseveralflowers。
Ihavenowrelievedmymindandwilltellthepurportofthisnote——viz。ifanyotherspeciesofThaliabesidesT。dealbatashouldflowerwithyou，fortheloveofheavenandallthesaints，sendmeafewinTINBOXWITHDAMP
MOSS。
Yourinsanefriend，CH。DARWIN。
[In1878Dr。Ogle’stranslationofKerner’sinterestingbook，’FlowersandtheirUnbiddenGuests，’waspublished。Myfather，whofeltmuchinterestinthetranslation（asappearsinthefollowingletter），contributedsomeprefatorywordsofapproval:]
CHARLESDARWINTOW。OGLE。
Down，December16[1878]……IhavenowreadKerner’sbook，whichisbettereventhanIanticipated。
Thetranslationseemstomeasclearasdaylight，andwritteninforcibleandgoodfamiliarEnglish。IamratherafraidthatitistoogoodfortheEnglishpublic，whichseemstolikeverywashyfood，unlessitbeadministeredbysomeonewhosenameiswell—known，andthenIsuspectagooddealoftheunintelligibleisverypleasingtothem。IhopetoheaventhatImaybewrong。Anyhow，youandMrs。OglehavedonearightgoodserviceforBotanicalScience。Yoursverysincerely，CH。DARWIN。
P。S。——Youhavedonememuchhonourinyourprefatoryremarks。
[OneofthelatestreferencestohisOrchid—workoccursinalettertoMr。
Bentham，February16，1880。Itshowstheamountofpleasurewhichthissubjectgavetomyfather，and（whatischaracteristicofhim）thathisreminiscenceoftheworkwasoneofdelightintheobservationswhichprecededitspublication。Nottotheapplausewhichfollowedit:——
"Theyarewonderfulcreatures，theseOrchids，andIsometimesthinkwithaglowofpleasure，whenIremembermakingoutsomelittlepointintheirmethodoffertilisation。"]
CHAPTER2。XI。
THE’EFFECTSOFCROSS—ANDSELF—FERTILISATIONINTHEVEGETABLEKINGDOM。’
1876。
[Thisbook，aspointedoutinthe’Autobiography，’isacomplementtothe’FertilisationofOrchids，’becauseitshowshowimportantaretheresultsofcross—fertilisationwhichareensuredbythemechanismsdescribedinthatbook。
Byprovingthattheoffspringofcross—fertilisationaremorevigorousthantheoffspringofself—fertilisation，heshowedthatonecircumstancewhichinfluencesthefateofyoungplantsinthestruggleforlifeisthedegreetowhichtheirparentsarefittedforcross—fertilisation。Hethusconvincedhimselfthattheintensityofthestruggle（whichhehadelsewhereshowntoexistamongyoungplants）isameasureofthestrengthofaselectiveagencyperpetuallysiftingouteverymodificationinthestructureofflowerswhichcaneffectitscapabilitiesforcross—
fertilisation。
Thebookisalsovaluableinanotherrespect，becauseitthrowslightonthedifficultproblemsoftheoriginofsexuality。Theincreasedvigourresultingfromcross—fertilisationisalliedintheclosestmannertotheadvantagegainedbychangeofconditions。Sostronglyisthisthecase，thatinsomeinstancescross—fertilisationgivesnoadvantagetotheoffspring，unlesstheparentshavelivedunderslightlydifferentconditions。SothatthereallyimportantthingisnotthattwoindividualsofdifferentBLOODshallunite，buttwoindividualswhichhavebeensubjectedtodifferentconditions。Wearethusledtobelievethatsexualityisameansforinfusingvigourintotheoffspringbythecoalescenceofdifferentiatedelements，anadvantagewhichcouldnotfollowifreproductionswereentirelyasexual。
Itisremarkablethatthisbook，theresultofelevenyearsofexperimentalwork，oweditsorigintoachanceobservation。MyfatherhadraisedtwobedsofLinariavulgaris——onesetbeingtheoffspringofcross—andtheotherofself—fertilisation。Theseplantsweregrownforthesakeofsomeobservationsoninheritance，andnotwithanyviewtocross—breeding，andhewasastonishedtoobservethattheoffspringofself—fertilisationwereclearlylessvigorousthantheothers。Itseemedincredibletohimthatthisresultcouldbeduetoasingleactofself—fertilisation，anditwasonlyinthefollowingyearwhenpreciselythesameresultoccurredinthecaseofasimilarexperimentoninheritanceinCarnations，thathisattentionwas"thoroughlyaroused"andthathedeterminedtomakeaseriesofexperimentsspeciallydirectedtothequestion。Thefollowinglettersgivesomeaccountoftheworkinquestion。]
CHARLESDARWINTOASAGRAY。
September10，[1866？]……Ihavejustbegunalargecourseofexperimentsonthegerminationoftheseed，andonthegrowthoftheyoungplantswhenraisedfromapistilfertilisedbypollenfromthesameflower，andfrompollenfromadistinctplantofthesame，orofsomeothervariety。Ihavenotmadesufficientexperimentstojudgecertainly，butinsomecasesthedifferenceinthegrowthoftheyoungplantsishighlyremarkable。Ihavetakeneverykindofprecautioningettingseedfromthesameplant，ingerminatingtheseedonmyownchimney—piece，inplantingtheseedlingsinthesameflower—pot，andunderthissimilartreatmentIhaveseentheyoungseedlingsfromthecrossedseedexactlytwiceastallastheseedlingsfromtheself—
fertilisedseed;bothseedshavinggerminatedonthesameday。IfIcanestablishthisfact（butperhapsitwillallgotothedogs），insomefiftycases，withplantsofdifferentorders，Ithinkitwillbeveryimportant，forthenweshallpositivelyknowwhythestructureofeveryflowerpermits，orfavours，ornecessitatesanoccasionalcrosswithadistinctindividual。ButallthisisrathercookingmyharebeforeIhavecaughtit。ButsomehowitisagreatpleasuretometotellyouwhatIamabout。
Believeme，mydearGray，Everyoursmosttruly，andwithcordialthanks，CH。DARWIN。
CHARLESDARWINTOG。BENTHAM。
April22，1868……Iamexperimentingonaverylargescaleonthedifferenceinpowerofgrowthbetweenplantsraisedfromself—fertilisedandcrossedseeds;anditisnoexaggerationtosaythatthedifferenceingrowthandvigourissometimestrulywonderful。Lyell，HuxleyandHookerhaveseensomeofmyplants，andbeenastonished;andIshouldmuchliketoshowthemtoyou。I
alwayssupposeduntillatelythatnoevileffectswouldbevisibleuntilafterseveralgenerationsofself—fertilisation;butnowIseethatonegenerationsometimessuffices;andtheexistenceofdimorphicplantsandallthewonderfulcontrivancesoforchidsarequiteintelligibletome。
Withcordialthanksforyourletter，whichhaspleasedmegreatly，Yoursverysincerely，CHARLESDARWIN。
[AnextractfromalettertoDr。Gray（March11，1873）mentionstheprogressofthework:——
"IworkedlastsummerhardatDrosera，butcouldnotfinishtillIgotfreshplants，andconsequentlytookuptheeffectsofcrossingandself—
fertilisingplants，andamgotsointerestedthatDroseramustgotothedogstillIfinishwiththis，andgetitpublished;butthenIwillresumemybelovedDrosera，andIheartilyapologiseforhavingsentthepreciouslittlethingsevenforamomenttothedogs。"
Thefollowinglettersgivetheauthor’simpressionofhisownbook。]
CHARLESDARWINTOJ。MURRAY。
Down，September16，1876。
MydearSir，Ihavejustreceivedproofsinsheetoffivesheets，soyouwillhavetodecidesoonhowmanycopieswillhavetobestruckoff。Idonotknowwhattoadvise。Thegreaterpartofthebookisextremelydry，andthewholeonaspecialsubject。Nevertheless，Iamconvincedthatthebookisofvalue，andIamconvincedthatforMANYyearscopieswillbeoccasionallysold。
Judgingfromthesaleofmyformerbooks，andfromsupposingthatsomepersonswillpurchaseittocompletethesetofmyworks，Iwouldsuggest1500。Butyoumustbeguidedbyyourlargerexperience。IwillonlyrepeatthatIamconvincedthebookisofsomepermanentvalue……
CHARLESDARWINTOVICTORCARUS。
Down，September27，1876。
MydearSir，Isentbythismorning’spostthefourfirstperfectsheetsofmynewbook，thetitleofwhichyouwillseeonthefirstpage，andwhichwillbepublishedearlyinNovember。
Iamsorrytosaythatitisonlyshorterbyafewpagesthanmy’InsectivorousPlants。’Thewholeisnowintype，thoughIhavecorrectedfinallyonlyhalfthevolume。Youwill，therefore，rapidlyreceivetheremainder。Thebookisverydull。ChaptersII。toVI。，inclusive，aresimplyarecordofexperiments。Nevertheless，Ibelieve（thoughamancanneverjudgehisownbooks）thatthebookisvaluable。Youwillhavetodecidewhetheritisworthtranslating。Ihopeso。Ithascostmeverygreatlabour，andtheresultsseemtomeremarkableandwellestablished。
Ifyoutranslateit，youcouldeasilygetaidforChaptersII。toVI。，asthereishereendless，butIhavethoughtnecessaryrepetition。Ishallbeanxioustohearwhatyoudecide……
Imostsincerelyhopethatyourhealthhasbeenfairlygoodthissummer。
MydearSir，yoursverytruly，CH。DARWIN。
CHARLESDARWINTOASAGRAY。
Down，October28，1876。
MydearGray，Isendbythispostallthecleansheetsasyetprinted，andIhopetosendtheremainderwithinafortnight。Pleaseobservethatthefirstsixchaptersarenotreadable，andthesixlastverydull。StillIbelievethattheresultsarevaluable。Ifyoureviewthebook，Ishallbeverycurioustoseewhatyouthinkofit，forIcaremoreforyourjudgmentthanforthatofalmostanyoneelse。Iknowalsothatyouwillspeakthetruth，whetheryouapproveordisapprove。Veryfewwilltakethetroubletoreadthebook，andIdonotexpectyoutoreadthewhole，butIhopeyouwillreadthelatterchapters……IamsosickofcorrectingthepressandlickingmyhorridbadstyleintointelligibleEnglish。
[The’EffectsofCrossandSelf—fertilisation’waspublishedonNovember10，1876，and1500copiesweresoldbeforetheendoftheyear。Thefollowingletterreferstoareviewin’Nature’（February15，1877。）:]
CHARLESDARWINTOW。THISELTONDYER。
Down，February16，1877。
DearDyer，ImusttellyouhowgreatlyIampleasedandhonouredbyyourarticlein’Nature，’whichIhavejustread。Youareanadeptinsayingwhatwillpleaseanauthor，notthatIsupposeyouwrotewiththisexpressintention。
Ishouldbeverywellcontentedtodeserveafractionofyourpraise。I
havealsobeenmuchinterested，andthisisbetterthanmerepleasure，byyourargumentabouttheseparationofthesexes。IdaresaythatIamwrong，andwillhereafterconsiderwhatyousaymorecarefully:butatpresentIcannotdriveoutofmyheadthatthesexesmusthaveoriginatedfromtwoindividuals，slightlydifferent，whichconjugated。ButIamawarethatsomecasesofconjugationareopposedtoanysuchviews。
Withheartythanks，Yourssincerely，CHARLESDARWIN。
CHAPTER2。XII。
’DIFFERENTFORMSOFFLOWERSONPLANTSOFTHESAMESPECIES。’
1877。
[Thevolumebearingtheabovetitlewaspublishedin1877，andwasdedicatedbytheauthortoProfessorAsaGray，"asasmalltributeofrespectandaffection。"Itconsistsofcertainearlierpapersre—edited，withtheadditionofaquantityofnewmatter。Thesubjectstreatedinthebookare:——
1。HeterostyledPlants。
2。Polygamous，Dioecious，andGynodioeciousPlants。
3。CleistogamicFlowers。
Thenatureofheterostyledplantsmaybeillustratedintheprimrose，oneofthebestknownexamplesoftheclass。Ifanumberofprimrosesbegathered，itwillbefoundthatsomeplantsyieldnothingbut"pin—eyed"
flowers，inwhichthestyle（ororganforthetransmissionofthepollentotheovule）islong，whiletheothersyieldonly"thrum—eyed"flowerswithshortstyles。Thusprimrosesaredividedintotwosetsorcastesdifferingstructurallyfromeachother。Myfathershowedthattheyalsodiffersexually，andthatinfactthebondbetweenthetwocastesmorenearlyresemblesthatbetweenseparatesexesthananyotherknownrelationship。
Thusforexamplealong—styledprimrose，thoughitcanbefertilisedbyitsownpollen，isnotFULLYfertileunlessitisimpregnatedbythepollenofashort—styledflower。Heterostyledplantsarecomparabletohermaphroditeanimals，suchassnails，whichrequiretheconcourseoftwoindividuals，althougheachpossessesboththesexualelements。ThedifferenceisthatinthecaseoftheprimroseitisPERFECTFERTILITY，andnotsimplyFERTILITY，thatdependsonthemutualactionofthetwosetsofindividuals。
Theworkonheterostyledplantshasaspecialbearing，towhichtheauthorattachedmuchimportance，ontheproblemoforiginofspecies。（See’Autobiography，’volumei。）
Hefoundthatawonderfullycloseparallelismexistsbetweenhybridisationandcertainformsoffertilisationamongheterostyledplants。Sothatitishardlyanexaggerationtosaythatthe"illegitimately"rearedseedlingsarehybrids，althoughboththeirparentsbelongtoidenticallythesamespecies。InalettertoProfessorHuxley，myfatherwritesasifhisresearchesonheterostyledplantstendedtomakehimbelievethatsterilityisaselectedoracquiredquality。Butinhislaterpublications，e。g。inthesixtheditionofthe’Origin，’headherestothebeliefthatsterilityisanincidentalratherthanaselectedquality。Theresultofhisworkonheterostyledplantsisofimportanceasshowingthatsterilityisnotestofspecificdistinctness，andthatitdependsondifferentiationofthesexualelementswhichisindependentofanyracialdifference。Iimaginethatitwashisinstinctiveloveofmakingoutadifficultywhichtoagreatextentkepthimatworksopatientlyontheheterostyledplants。Butitwasthefactthatgeneralconclusionsoftheabovecharactercouldbedrawnfromhisresultswhichmadehimthinkhisresultsworthyofpublication。（See’FormsofFlowers，’page243。）