AsformyselfIamtakingafortnight’srest，aftersendingapileofMS。
totheprinters，anditwasapieceofgoodfortunethatyourbookarrivedasIwasgettingintomycarriage，forIwantedsomethingtoreadwhilstawayfromhome。MyMS。relatestothemovementsofplants，andIthinkthatIhavesucceededinshowingthatallthemoreimportantgreatclassesofmovementsareduetothemodificationofakindofmovementcommontoallpartsofallplantsfromtheirearliestyouth。
Praygivemykindremembrancestoyourson，andwithmyhighestrespectandbestthanks，Believeme，mydearSir，yoursverysincerely，CHARLESDARWIN。
P。S。——Italwayspleasesmetoexaltplantsintheorganicscale，andifyouwilltakethetroubletoreadmylastchapterwhenmybook（whichwillbesadlytoobig）ispublishedandsenttoyou，Ihopeandthinkthatyoualsowilladmiresomeofthebeautifuladaptationsbywhichseedlingplantsareenabledtoperformtheirproperfunctions。
[ThebookwaspublishedonNovember6，1880，and1500copiesweredisposedofatMr。Murray’ssale。WithregardtoithewrotetoSirJ。D。Hooker（November23）:——
"Yournotehaspleasedmemuch——forIdidnotexpectthatyouwouldhavehadtimetoreadANYofit。Readthelastchapter，andyouwillknowthewholeresult，butwithouttheevidence。Thecase，however，ofradiclesbendingafterexposureforanhourtogeotropism，withtheirtips（orbrains）cutoffis，Ithink，worthyourreading（bottomofpage525）;itastoundedme。Thenextmostremarkablefact，asitappearedtome（page148），isthediscriminationofthetipoftheradiclebetweenaslightlyharderandsofterobjectaffixedonoppositesidesoftip。ButIwillbotheryounomoreaboutmybook。Thesensitivenessofseedlingstolightismarvellous。"
Toanotherfriend，Mr。ThiseltonDyer，hewrote（November28，1880）:——
"Verymanythanksforyourmostkindnote，butyouthinktoohighlyofourwork，notbutwhatthisisverypleasant……ManyoftheGermansareverycontemptuousaboutmakingouttheuseoforgans;buttheymaysneerthesoulsoutoftheirbodies，andIforoneshallthinkitthemostinterestingpartofNaturalHistory。Indeedyouaregreatlymistakenifyoudoubtforonemomentontheverygreatvalueofyourconstantandmostkindassistancetous。"
Thebookwaswidelyreviewed，andexcitedmuchinterestamongthegeneralpublic。Thefollowingletterreferstoaleadingarticleinthe"Times"，November20，1880:]
CHARLESDARWINTOMRS。HALIBURTON。（Mrs。Haliburtonwasadaughterofmyfather’searlyfriend，thelateMr。Owen，ofWoodhouse。）
Down，November22，1880。
MydearSarah，YouseehowaudaciouslyIbegin;butIhavealwayslovedandshalleverlovethisname。Yourletterhasdonemorethanpleaseme，foritskindnesshastouchedmyheart。IoftenthinkofolddaysandofthedelightofmyvisitstoWoodhouse，andofthedeepdebtofgratitudeIowetoyourfather。Itwasverygoodofyoutowrite。IhadquiteforgottenmyoldambitionabouttheShrewsburynewspaper（Mrs。HaliburtonhadremindedhimofhissayingasaboythatifEddowes’newspapereveralludedtohimas"ourdeservingfellow—townsman，"hisambitionwouldbeamplygratified。）;
butIrememberthepridewhichIfeltwhenIsawinabookaboutbeetlestheimpressivewords"capturedbyC。Darwin。"Capturedsoundedsograndcomparedwithcaught。Thisseemedtomegloryenoughforanyman！Idonotknowintheleastwhatmadethe"Times"glorifyme（Thefollowingistheopeningsentenceoftheleadingarticle:——"OfallourlivingmenofsciencenonehavelabouredlongerandtomoresplendidpurposethanMr。
Darwin。"），forithassometimespitchedintomeferociously。
Ishouldverymuchliketoseeyouagain，butyouwouldfindavisithereverydull，forwefeelveryoldandhavenoamusement，andleadasolitarylife。ButweintendinafewweekstospendafewdaysinLondon，andthenifyouhaveanythingelsetodoinLondon，youwouldperhapscomeandlunchwithus。（MyfatherhadthepleasureofseeingMrs。Haliburtonathisbrother’shouseinQueenAnneStreet。）
Believeme，mydearSarah，Yoursgratefullyandaffectionately，CHARLESDARWIN。
[Thefollowingletterwascalledforthbythepublicationofavolumedevotedtothecriticismofthe’PowerofMovementinPlants’byanaccomplishedbotanist，Dr。JuliusWiesner，ProfessorofBotanyintheUniversityofVienna:]
CHARLESDARWINTOJULIUSWIESNER。
Down，October25th，1881。
MydearSir，Ihavenowfinishedyourbook（’DasBewegungsvermogenderPflanzen。’
Vienna，1881。），andhaveunderstoodthewholeexceptaveryfewpassages。
Inthefirstplace，letmethankyoucordiallyforthemannerinwhichyouhaveeverywheretreatedme。Youhaveshownhowamanmaydifferfromanotherinthemostdecidedmanner，andyetexpresshisdifferencewiththemostperfectcourtesy。NotafewEnglishandGermannaturalistsmightlearnausefullessonfromyourexample;forthecoarselanguageoftenusedbyscientificmentowardseachotherdoesnogood，andonlydegradesscience。
Ihavebeenprofoundlyinterestedbyyourbook，andsomeofyourexperimentsaresobeautiful，thatIactuallyfeltpleasurewhilebeingvivisected。Itwouldtakeuptoomuchspacetodiscussalltheimportanttopicsinyourbook。IfearthatyouhavequiteupsettheinterpretationwhichIhavegivenoftheeffectsofcuttingoffthetipsofhorizontallyextendedroots，andofthoselaterallyexposedtomoisture;butIcannotpersuademyselfthatthehorizontalpositionoflateralbranchesandrootsisduesimplytotheirlessenedpowerofgrowth。NorwhenIthinkofmyexperimentswiththecotyledonsofPhalaris，canIgiveupthebeliefofthetransmissionofsomestimulusduetolightfromtheuppertothelowerpart。Atpage60youhavemisunderstoodmymeaning，whenyousaythatI
believethattheeffectsfromlightaretransmittedtoapartwhichisnotitselfheliotropic。Ineverconsideredwhetherornottheshortpartbeneaththegroundwasheliotropic;butIbelievethatwithyoungseedlingsthepartwhichbendsNEAR，butABOVEthegroundisheliotropic，andI
believesofromthispartbendingonlymoderatelywhenthelightisoblique，andbendingrectangularlywhenthelightishorizontal。
Neverthelessthebendingofthislowerpart，asIconcludefrommyexperimentswithopaquecaps，isinfluencedbytheactionoflightontheupperpart。Myopinion，however，ontheaboveandmanyotherpoints，signifiesverylittle，forIhavenodoubtthatyourbookwillconvincemostbotaniststhatIamwronginallthepointsonwhichwediffer。
Independentlyofthequestionoftransmission，mymindissofulloffactsleadingmetobelievethatlight，gravity，etc。，actnotinadirectmannerongrowth，butasstimuli，thatIamquiteunabletomodifymyjudgmentonthishead。Icouldnotunderstandthepassageatpage78，untilI
consultedmysonGeorge，whoisamathematician。Hesupposesthatyourobjectionisfoundedonthediffusedlightfromthelampilluminatingbothsidesoftheobject，andnotbeingreduced，withincreasingdistanceinthesameratioasthedirectlight;buthedoubtswhetherthisNECESSARY
correctionwillaccountfortheverylittledifferenceintheheliotropiccurvatureoftheplantsinthesuccessivepots。
Withrespecttothesensitivenessofthetipsofrootstocontact，IcannotadmityourviewuntilitisprovedthatIaminerroraboutbitsofcardattachedbyliquidgumcausingmovement;whereasnomovementwascausedifthecardremainedseparatedfromthetipbyalayeroftheliquidgum。Thefactalsoofthickerandthinnerbitsofcardattachedonoppositesidesofthesamerootbyshellac，causingmovementinonedirection，hastobeexplained。Youoftenspeakofthetiphavingbeeninjured;butexternallytherewasnosignofinjury:andwhenthetipwasplainlyinjured，theextremepartbecamecurvedTOWARDStheinjuredside。Icannomorebelievethatthetipwasinjuredbythebitsofcard，atleastwhenattachedbygum—water，thanthattheglandsofDroseraareinjuredbyaparticleofthreadorhairplacedonit，orthatthehumantongue[isso]whenitfeelsanysuchobject。
Aboutthemostimportantsubjectinmybook，namelycircumnutation，IcanonlysaythatIfeelutterlybewilderedatthedifferenceinourconclusions;butIcouldnotfullyunderstandsomepartswhichmysonFranciswillbeabletotranslatetomewhenhereturnshome。Thegreaterpartofyourbookisbeautifullyclear。
Finally，IwishthatIhadenoughstrengthandspirittocommenceafreshsetofexperiments，andpublishtheresults，withafullrecantationofmyerrorswhenconvincedofthem;butIamtoooldforsuchanundertaking，nordoIsupposethatIshallbeabletodomuch，oranymore，originalwork。IimaginethatIseeonepossiblesourceoferrorinyourbeautifulexperimentofaplantrotatingandexposedtoalaterallight。
Withhighrespectandwithsincerethanksforthekindmannerinwhichyouhavetreatedmeandmymistakes，Iremain，mydearSir，yourssincerely，CHARLESDARWIN。
CHAPTER2。XV。
MISCELLANEOUSBOTANICALLETTERS。
1873—1882。
[Thepresentchaptercontainsaseriesofmiscellaneouslettersonbotanicalsubjects。Someofthemshowmyfather’svariedinterestsinbotanicalscience，andothersgiveaccountofresearcheswhichneverreachedcompletion。]
BLOOMONLEAVESANDFRUIT。
[Hisresearchesintothemeaningofthe"bloom，"orwaxycoatingfoundonmanyleaves，wasoneofthoseinquirieswhichremainedunfinishedatthetimeofhisdeath。Heamassedaquantityofnotesonthesubject，partofwhichIhopetopublishatnodistantdate。（Asmallinstalmentontherelationbetweenbloomandthedistributionofthestomataonleaveshasappearedinthe’JournaloftheLinneanSociety，’1886。Tschirsch（"Linnaea"，1881）haspublishedresultsidenticalwithsomewhichmyfatherandmyselfobtained，viz。thatbloomdiminishestranspiration。ThesamefactwaspreviouslypublishedbyGarreauin1850。）
OneofhisearliestlettersonthissubjectwasaddressedinAugust，1873，toSirJosephHooker:——
"Iwantalittleinformationfromyou，andifyoudonotyourselfknow，pleasetoenquireofsomeofthewisemenofKew。
"Whyaretheleavesandfruitofsomanyplantsprotectedbyathinlayerofwaxymatter（likethecommoncabbage），orwithfinehair，sothatwhensuchleavesorfruitareimmersedinwatertheyappearasifencasedinthinglass？Itisreallyaprettysighttoputapodofthecommonpea，oraraspberryintowater。Ifindseveralleavesarethusprotectedontheundersurfaceandnotontheupper。
"Howcanwaterinjuretheleavesifindeedthisisatallthecase？"
OnthislatterpointhewrotetoSirThomasFarrer:——
"Iamnowbecomemadaboutdropsofwaterinjuringleaves。PleaseaskMr。
Paine（SirThomasFarrer’sgardener。）whetherhebelieves，FROMHISOWN
EXPERIENCE，thatdropsofwaterinjureleavesorfruitinhisconservatories。Itissaidthatthedropsactasburning—glasses;ifthisistrue，theywouldnotbeatallinjuriousoncloudydays。Asheissoacuteaman，Ishouldverymuchliketohearhisopinion。IrememberwhenIgrewhot—houseorchidsIwascautionednottowettheirleaves;butI
neverthenthoughtonthesubject。
"Ienjoyedmyvisitgreatlywithyou，andIamverysurethatallEnglandcouldnotaffordakinderandpleasanterhost。"
Someyearslaterhetookupthesubjectagain，andwrotetoSirJosephHooker（May25，1877）:——
"Ihavebeenlookingovermyoldnotesaboutthe"bloom"onplants，andI
thinkthatthesubjectiswellworthpursuing，thoughIamverydoubtfulofanysuccess。Areyouinclinedtoaidmeonthemerechanceofsuccess，forwithoutyouraidIcoulddohardlyanything？"]
CHARLESDARWINTOASAGRAY。
Down，June4[1877]……Iamnowtryingtomakeouttheuseorfunctionof"bloom，"orthewaxysecretionontheleavesandfruitofplants，butamVERYdoubtfulwhetherI
shallsucceed。Canyougivemeanylight？Aresuchplantscommonerinwarmthanincolderclimates？IaskbecauseIoftenwalkoutinheavyrain，andtheleavesofveryfewwilddicotyledonscanbehereseenwithdropsofwaterrollingoffthemlikequick—silver。Whereasinmyflowergarden，greenhouse，andhot—housesthereareseveral。Again，arebloom—
protectedplantscommononyourDRYwesternplains？HookerTHINKSthattheyarecommonattheCapeofGoodHope。Itisapuzzletomeiftheyarecommonunderverydryclimates，andIfindbloomverycommonontheAcaciasandEucalyptiofAustralia。SomeoftheEucalyptiwhichdonotappeartobecoveredwithbloomhavetheepidermisprotectedbyalayerofsomesubstancewhichisdissolvedinboilingalcohol。Arethereanybloom—
protectedleavesorfruitintheArcticregions？Ifyoucanilluminateme，asyousooftenhavedone，praydoso;butotherwisedonotbotheryourselfbyanswering。
Yoursaffectionately，C。DARWIN。
CHARLESDARWINTOW。THISELTONDYER。
Down，September5[1877]。
MydearDyer，Onewordtothankyou。Ideclarehaditnotbeenforyourkindness，weshouldhavebrokendown。Asitiswehavemadeoutclearlythatwithsomeplants（chieflysucculent）thebloomchecksevaporation——withsomecertainlypreventsattacksofinsects;withSOMEsea—shoreplantspreventsinjuryfromsalt—water，and，Ibelieve，withafewpreventsinjuryfrompurewaterrestingontheleaves。Thislatterisasyetthemostdoubtfulandthemostinterestingpointinrelationtothemovementsofplants……
CHARLESDARWINTOF。MULLER。
Down，July4[1881]。
MydearSir，Yourkindnessisunbounded，andIcannottellyouhowmuchyourlastletter（May31）hasinterestedme。Ihavepilesofnotesabouttheeffectofwaterrestingonleaves，andtheirmovements（asIsupposed）toshakeoffthedrops。ButIhavenotlookedoverthesenotesforalongtime，andhadcometothinkthatperhapsmynotionwasmerefancy，butIhadintendedtobeginexperimentingassoonasIreturnedhome;andnowwithyourINVALUABLEletteraboutthepositionoftheleavesofvariousplantsduringrain（IhaveoneanalogouscasewithAcaciafromSouthAfrica），Ishallbestimulatedtoworkinearnest。
VARIABILITY。
[Thefollowingletterreferstoasubjectonwhichmyfatherfeltthestrongestinterest:——theexperimentalinvestigationofthecausesofvariability。Theexperimentsalludedtoweretosomeextentplannedout，andsomepreliminaryworkwasbeguninthedirectionindicatedbelow，buttheresearchwasultimatelyabandoned。]
CHARLESDARWINTOJ。H。GILBERT。（Dr。Gilbert，F。R。S。，jointauthorwithSirJohnBennettLawesofalongseriesofvaluableresearchesinScientificAgriculture。）
Down，February16，1876。
MydearSir，WhenImetyouattheLinneanSociety，youweresokindastosaythatyouwouldaidmewithadvice，andthiswillbeoftheutmostvaluetomeandmyson。Iwillfirststatemyobject，andhopethatyouwillexcusealongletter。Itisadmittedbyallnaturaliststhatnoproblemissoperplexingaswhatcausesalmosteverycultivatedplanttovary，andnoexperimentsasyettriedhavethrownanylightonthesubject。NowforthelasttenyearsIhavebeenexperimentingincrossingandself—fertilisingplants;andoneindirectresulthassurprisedmemuch;namely，thatbytakingpainstocultivateplantsinpotsunderglassduringseveralsuccessivegenerations，undernearlysimilarconditions，andbyself—fertilisingthemineachgeneration，thecolouroftheflowersoftenchanges，and，whatisveryremarkable，theybecameinsomeofthemostvariablespecies，suchasMimulus，Carnation，etc。，quiteconstant，likethoseofawildspecies。
Thisfactandseveralothershaveledmetothesuspicionthatthecauseofvariationmustbeindifferentsubstancesabsorbedfromthesoilbytheseplantswhentheirpowersofabsorptionarenotinterferedwithbyotherplantswithwhichtheygrowmingledinastateofnature。ThereforemysonandIwishtogrowplantsinpotsinsoilentirely，orasnearlyentirelyasispossible，destituteofallmatterwhichplantsabsorb，andthentogiveduringseveralsuccessivegenerationstoseveralplantsofthesamespeciesasdifferentsolutionsasmaybecompatiblewiththeirlifeandhealth。Andnow，canyouadvisemehowtomakesoilapproximatelyfreeofallthesubstanceswhichplantsnaturallyabsorb？Isupposewhitesilversand，soldforcleaningharness，etc。，isnearlypuresilica，butwhatamI
todoforalumina？WithoutsomealuminaIimaginethatitwouldbeimpossibletokeepthesoildampandfitforthegrowthofplants。I
presumethatclaywashedoverandoveragaininwaterwouldstillyieldmineralmattertothecarbonicacidsecretedbytheroots。Ishouldwantagooddealofsoil，foritwouldbeuselesstoexperimentiseunlesswecouldfillfromtwentytothirtymoderatelysizedflower—potseveryyear。Canyousuggestanyplan？forunlessyoucanitwould，Ifear，beuselessforustocommenceanattempttodiscoverwhethervariabilitydependsatallonmatterabsorbedfromthesoil。Afterobtainingtherequisitekindofsoil，mynotionistowateronesetofplantswithnitrateofpotassium，anothersetwithnitrateofsodium，andanotherwithnitrateoflime，givingallasmuchphosphateofammoniaastheyseemedtosupport，forIwishtheplantstogrowasluxuriantlyaspossible。TheplantswateredwithnitrateofNaandofCawouldrequire，Isuppose，someK;butperhapstheywouldgetwhatisabsolutelynecessaryfromsuchsoilasIshouldbeforcedtoemploy，andfromtherain—watercollectedintanks。Icouldusehardwaterfromadeepwellinthechalk，butthenalltheplantswouldgetlime。IftheplantstowhichIgiveNitrateofNaandofCawouldnotgrowImightgivethemalittlealum。
IamwellawarehowveryignorantIam，andhowcrudemynotionsare;andifyoucouldsuggestanyothersolutionsbywhichplantswouldbelikelytobeaffecteditwouldbeaverygreatkindness。Isupposethattherearenoorganicfluidswhichplantswouldabsorb，andwhichIcouldprocure？
Imusttrusttoyourkindnesstoexcusemefortroublingyouatsuchlength，and，Iremain，dearSir，yourssincerely，CHARLESDARWIN。
[ThenextlettertoProfessorSemper（ProfessorofZoologyatWurzburg。）
bearsonthesamesubject:]
FROMCHARLESDARWINTOK。SEMPER。
Down，July19，1881。
MydearProfessorSemper，Ihavebeenmuchpleasedtoreceiveyourletter，butIdidnotexpectyoutoanswermyformerone……IcannotrememberwhatIwrotetoyou，butIamsurethatitmusthaveexpressedtheinterestwhichIfeltinreadingyourbook。（Publishedinthe’InternationalScientificSeries，’in1881，underthetitle，’TheNaturalConditionsofExistenceastheyaffectAnimalLife。’）IthoughtthatyouattributedtoomuchweighttotheDIRECTactionoftheenvironment;butwhetherIsaidsoIknownot，forwithoutbeingaskedIshouldhavethoughtitpresumptuoustohavecriticisedyourbook，norshouldInowsaysohadInotduringthelastfewdaysbeenstruckwithProfessorHoffmann’sreviewofhisownworkinthe’BotanischeZeitung，’onthevariabilityofplants;anditisreallysurprisinghowlittleeffectheproducedbycultivatingcertainplantsunderunnaturalconditions，asthepresenceofsalt，lime，zinc，etc。，etc。，duringSEVERALgenerations。
Plants，moreover，wereselectedwhichwerethemostlikelytovaryundersuchconditions，judgingfromtheexistenceofclosely—alliedformsadaptedfortheseconditions。NodoubtIoriginallyattributedtoolittleweighttothedirectactionofconditions，butHoffmann’spaperhasstaggeredme。
Perhapshundredsofgenerationsofexposurearenecessary。Itisamostperplexingsubject。IwishIwasnotsoold，andhadmorestrength，forI
seelinesofresearchtofollow。Hoffmannevendoubtswhetherplantsvarymoreundercultivationthanintheirnativehomeandundertheirnaturalconditions。Ifso，theastonishingvariationsofalmostallcultivatedplantsmustbeduetoselectionandbreedingfromthevaryingindividuals。
Thisideacrossedmymindmanyyearsago，butIwasafraidtopublishit，asIthoughtthatpeoplewouldsay，"howhedoesexaggeratetheimportanceofselection。"
IstillMUSTbelievethatchangedconditionsgivetheimpulsetovariability，butthattheyactINMOSTCASESinaveryindirectmanner。
But，asIsaid，itisamostperplexingproblem。Prayforgivemeforwritingatsuchlength;IhadnointentionofdoingsowhenIsatdowntowrite。
Iamextremelysorrytohear，foryourownsakeandforthatofScience，thatyouaresohardworked，andthatsomuchofyourtimeisconsumedinofficiallabour。
Praybelieveme，dearProfessorSemper，Yourssincerely，CHARLESDARWIN。
GALLS。
[Shortlybeforehisdeath，myfatherbegantoexperimentiseonthepossibilityofproducinggallsartificially。AlettertoSirJ。D。Hooker（November3，1880）showstheinterestwhichhefeltinthequestion:——
"IwasdelightedwithPaget’sEssay（’DiseaseinPlants，’bySirJamesPaget。——See"Gardeners’Chronicle"，1880。）;Ihearthathehasoccasionallyattendedtothissubjectfromhisyouth……Iamverygladhehascalledattentiontogalls:thishasalwaysseemedtomeaprofoundlyinterestingsubject;andifIhadbeenyoungerwouldtakeitup。"
Hisinterestinthissubjectwasconnectedwithhisever—presentwishtolearnsomethingofthecausesofvariation。Heimaginedtohimselfwonderfulgallscausedtoappearontheovariesofplants，andbythesemeanshethoughtitpossiblethattheseedmightbeinfluenced，andthusnewvarietiesarise。Hemadeaconsiderablenumberofexperimentsbyinjectingvariousreagentsintothetissuesofleaves，andwithsomeslightindicationsofsuccess。]
AGGREGATION。
[Thefollowinglettergivesanideaofthesubjectofthelastofhispublishedpapers。（’JournaloftheLinneanSociety。’volumexix，1882，pages239and262。）Theappearanceswhichheobservedinleavesandrootsattractedhim，onaccountoftheirrelationtothephenomenaofaggregationwhichhadsodeeplyinterestedhimwhenhewasatworkonDrosera:]
CHARLESDARWINTOS。H。VINES。（ReaderinBotanyintheUniversityofCambridge。）
Down，November1，1881。
MydearMr。Vines，AsIknowhowbusyyouare，itisagreatshametotroubleyou。Butyouaresorichinchemicalknowledgeaboutplants，andIamsopoor，thatI
appealtoyourcharityasapauper。Myquestionis——Doyouknowofanysolidsubstanceinthecellsofplantswhichglycerineandwaterdissolves？
ButyouwillunderstandmyperplexitybetterifIgiveyouthefacts:I
mentionedtoyouthatifaplantofEuphorbiapeplusisgentlydugupandtherootsplacedforashorttimeinaweaksolution（1to10，000ofwater，sufficesin24hours）ofcarbonateofammoniathe（generally）alternatelongitudinalrowsofcellsineveryrootlet，fromtheroot—capuptotheverytopoftheroot（butnotasfarasIhaveyetseeninthegreenstem）
becomefilledwithtranslucent，brownishgrainsofmatter。Theseroundedgrainsoftencohereandevenbecomeconfluent。Purephosphateandnitrateofammoniaproduce（thoughmoreslowly）thesameeffect，asdoespurecarbonateofsoda。
Now，ifslicesofrootunderacover—glassareirrigatedwithglycerineandwater，everyoneoftheinnumerablegrainsinthecellsdisappearaftersomehours。WhatamItothinkofthis。？……
Forgivemeforbotheringyoutosuchanextent;butImustmentionthatiftherootsaredippedinboilingwaterthereisnodepositionofmatter，andcarbonateofammoniaafterwardsproducesnoeffect。IshouldstatethatI
nowfindthatthegranularmatterisformedinthecellsimmediatelybeneaththethinepidermis，andafewothercellsnearthevasculartissue。
Ifthegranulesconsistedoflivingprotoplasm（butIcanseenotracesofmovementinthem），thenIshouldinferthattheglycerinekilledthemandaggregationceasedwiththediffusionofinvisiblyminuteparticles，forI
haveseenananalogousphenomenoninDrosera。
Ifyoucanaidme，praydoso，andanyhowforgiveme。
Yoursverysincerely，CH。DARWIN。
MR。TORBITT’SEXPERIMENTSONTHEPOTATO—DISEASE。
[Mr。JamesTorbitt，ofBelfast，hasbeenengagedforthelasttwelveyearsinthedifficultundertaking，inwhichhehasbeentoalargeextentsuccessful，ofraisingfungus—proofvarietiesofthepotato。MyfatherfeltgreatinterestinMr。Torbitt’swork，andcorrespondedwithhimfrom1876onwards。Thefollowingletter，givingaclearaccountofMr。
Torbitt’smethodandofmyfather’sopinionoftheprobabilityofitssuccess，waswrittenwiththeideathatGovernmentaidfortheworkmightpossiblybeobtainable:]
CHARLESDARWINTOT。H。FARRER。
Down，March2，1878。
MydearFarrer，Mr。Torbitt’splanofovercomingthepotato—diseaseseemstomebyfarthebestwhichhaseverbeensuggested。Itconsists，asyouknowfromhisprintedletter，ofrearingavastnumberofseedlingsfromcross—fertilisedparents，exposingthemtoinfection，ruthlesslydestroyingallthatsuffer，savingthosewhichresistbest，andrepeatingtheprocessinsuccessiveseminalgenerations。Mybeliefintheprobabilityofgoodresultsfromthisprocessrestsonthefactofallcharacterswhateveroccasionallyvarying。Itisknown，forinstance，thatcertainspeciesandvarietiesofthevineresistphylloxerabetterthanothers。AndrewKnightfoundinonevarietyorspeciesoftheapplewhichwasnotintheleastattackedbycoccus，andanothervarietyhasbeenobservedinSouthAustralia。Certainvarietiesofthepeachresistmildew，andseveralothersuchcasescouldbegiven。Thereforethereisnogreatimprobabilityinanewvarietyofpotatoarisingwhichwouldresistthefunguscompletely，oratleastmuchbetterthananyexistingvariety。Withrespecttothecross—fertilisationoftwodistinctseedlingplants，ithasbeenascertainedthattheoffspringthusraisedinheritmuchmorevigorousconstitutionsandgenerallyaremoreprolificthanseedlingsfromself—fertilisedparents。Itisalsoprobablethatcross—fertilisationwouldbeespeciallyvaluableinthecaseofthepotato，asthereisreasontobelievethattheflowersareseldomcrossedbyournativeinsects;andsomevarietiesareabsolutelysterileunlessfertilisedwithpollenfromadistinctvariety。Thereissomeevidencethatthegoodeffectsfromacrossaretransmittedforseveralgenerations;
itwouldnot，thereforebenecessarytocross—fertilisetheseedlingsineachgeneration，thoughthiswouldbedesirable，asitisalmostcertainthatagreaternumberofseedswouldthusbeobtained。Itshouldberememberedthatacrossbetweenplantsraisedfromthetubersofthesameplant，thoughgrowingondistinctroots，doesnomoregoodthanacrossbetweenflowersonthesameindividual。Consideringthewholesubject，itappearstomethatitwouldbeanationalmisfortuneifthecross—
fertilisedseedsinMr。Torbitt’spossessionproducedbyparentswhichhavealreadyshownsomepowerofresistingthedisease，arenotutilisedbytheGovernment，orsomepublicbody，andtheprocessofselectioncontinuedduringseveralmoregenerations。
ShouldtheAgriculturalSocietyundertakethework，Mr。Torbitt’sknowledgegainedbyexperiencewouldbeespeciallyvaluable;andanoutlineoftheplanisgiveninhisprintedletter。Itwouldbenecessarythatallthetubersproducedbyeachplantshouldbecollectedseparately，andcarefullyexaminedineachsucceedinggeneration。
Itwouldbeadvisablethatsomekindofpotatoeminentlyliabletothediseaseshouldbeplantedinconsiderablenumbersneartheseedlingssoastoinfectthem。
Altogetherthetrialwouldbeonerequiringmuchcareandextremepatience，asIknowfromexperiencewithanalogouswork，anditmaybefearedthatitwouldbedifficulttofindanyonewhowouldpursuetheexperimentwithsufficientenergy。Itseems，therefore，tomehighlydesirablethatMr。
Torbittshouldbeaidedwithsomesmallgrantsoastocontinuetheworkhimself。
Judgingfromhisreports，hiseffortshavealreadybeencrownedinsoshortatimewithmoresuccessthancouldhavebeenanticipated;andIthinkyouwillagreewithme，thatanyonewhoraisesafungus—proofpotatowillbeapublicbenefactorofnocommonkind。
MydearFarrer，yourssincerely，CHARLESDARWIN。
[AfterfurtherconsultationwithSirThomasFarrerandwithMr。Caird，myfatherbecameconvincedthatitwashopelesstoattempttoobtainGovernmentaid。HewrotetoMr。Torbitttothiseffect，adding，"itwouldbelesstroubletogetupasubscriptionfromafewrichleadingagriculturiststhanfromGovernment。ThisplanIthinkyoucannotobjectto，asyouhaveaskednothing，andwillhavenothingwhatevertodowiththesubscription。Infact，theaffairis，inmyopinion，acomplimenttoyou。"Theideaherebroachedwascarriedout，andMr。TorbittwasenabledtocontinuehisworkbytheaidofasumtowhichSirT。Farrer，Mr。Caird，myfather，andafewfriends，subscribed。
Myfather’ssympathyandencouragementwerehighlyvaluedbyMr。Torbitt，whotellsmethatwithoutthemheshouldlongagohavegivenuphisattempt。Afewextractswillillustratemyfather’sfellowfeelingwithMr。Torbitt’senergyandperseverance:——
"Iadmireyourindomitablespirit。Ifanyoneeverdeservedsuccess，youdoso，andIkeeptomyoriginalopinionthatyouhaveaverygoodchanceofraisingafungus—proofvarietyofthepotato。
"Apioneerinanewundertakingissuretomeetwithmanydisappointments，soIhopethatyouwillkeepupyourcourage，thoughwehavedonesoverylittleforyou。"
Mr。Torbitttellsmethathestill（1887）succeedsinraisingvarietiespossessingwell—markedpowersofresistingdisease;butthisimmunityisnotpermanent，and，aftersomeyears，thevarietiesbecomeliabletotheattacksofthefungus。]
THEKEWINDEXOFPLANT—NAMES，OR’NOMENCLATORDARWINIANUS。’
[Someaccountofmyfather’sconnectionwiththeIndexofPlant—namesnow（1887）incourseofpreparationatKewwillbefoundinMr。B。DaydonJackson’spaperinthe’JournalofBotany，’1887，page151。Mr。JacksonquotesthefollowingstatementbySirJ。D。Hooker:——
"Shortlybeforehisdeath，Mr。CharlesDarwininformedSirJosephHookerthatitwashisintentiontodevoteaconsiderablesumofmoneyannuallyforsomeyearsinaidorfurtheranceofsomeworkorworksofpracticalutilitytobiologicalscience，andtomakeprovisionsinhiswillintheeventofthesenotbeingcompletedduringhislifetime。
"Amongstotherobjectsconnectedwithbotanicalscience，Mr。Darwinregardedwithespecialinteresttheimportanceofacompleteindextothenamesandauthorsofthegeneraandspeciesofplantsknowntobotanists，togetherwiththeirnativecountries。Steudel’s’Nomenclator’istheonlyexistingworkofthisnature，andalthoughnownearlyhalfacenturyold，Mr。Darwinhadfounditofgreataidinhisownresearches。Ithasbeenindispensabletoeverybotanicalinstitution，whetherasalistofallknownfloweringplants，asanindicationoftheirauthors，orasadigestofbotanicalgeography。"
Since1840，whenthe’Nomenclator’waspublished，thenumberofdescribedplantsmaybesaidtohavedoubled，sothatthe’Nomenclator’isnowseriouslybelowtherequirementsofbotanicalwork。Toremedythiswant，the’Nomenclator’hasbeenfromtimetotimepostedupinaninterleavedcopyintheHerbariumatKew，bythehelpof"fundssuppliedbyprivateliberality。"（KewGardensReport，1881，page62。）