Raphanusraphanistrumandsativushaveoftenbeenrankedasdistinctspecies，andowingtodifferencesintheirfruitevenasdistinctgenera;
butProfessorHoffman（’Bot。Zeitung’1872page482）hasnowshownthatthesedifferences，remarkableastheyare，graduateaway，thefruitofR。
caudatusbeingintermediate。BycultivatingR。raphanistrumduringseveralgenerations（ibid1873page9），ProfessorHoffmanalsoobtainedplantsbearingfruitslikethoseofR。sativus。
PEA（Pisumsativum）。
Mostbotanistslookatthegarden—peaasspecificallydistinctfromthefield—pea（P。arvense）。ThelatterexistsinawildstateinSouthernEurope;buttheaboriginalparentofthegarden—peahasbeenfoundbyonecollectoralone，ashestates，intheCrimea。（9/81。Alph。DeCandolle’Geograph。Bot。’960。Mr。Bentham’Hort。Journal’volume91855page141
believesthatgardenandfieldpeasbelongtothesamespecies，andinthisrespecthediffersfromDr。Targioni。）AndrewKnightcrossed，asIaminformedbytheRev。A。Fitch，thefield—peawithawell—knowngardenvariety，thePrussianpea，andthecrossseemstohavebeenperfectlyfertile。Dr。Alefieldhasrecentlystudied（9/82。’BotanischeZeitung’1860
s。204。）thegenuswithcare，and，afterhavingcultivatedaboutfiftyvarieties，concludesthatcertainlytheyallbelongtothesamespecies。Itisaninterestingfactalreadyalludedto，that，accordingtoO。Heer（9/83。’DiePflanzenderPfahlbauten’1866s。23。）thepeasfoundinthelake—habitationsofSwitzerlandoftheStoneandBronzeages，belongtoanextinctvariety，withexceedinglysmallseeds，alliedtoP。arvenseorthefield—pea。Thevarietiesofthecommongarden—peaarenumerous，anddifferconsiderablyfromoneanother。ForcomparisonIplantedatthesametimeforty—one，EnglishandFrenchvarieties。Theydifferedgreatlyinheight，——
namelyfrombetween6and12inchesto8feet（9/84。AvarietycalledtheRouncivaattainsthisheight，asisstatedbyMr。Gordonin’Transact。
Hort。Soc。’2ndseriesvolume11835page374fromwhichpaperIhavetakensomefacts。），——inmannerofgrowth，andinperiodofmaturity。Somedifferingeneralaspectevenwhileonlytwoorthreeinchesinheight。ThestemsofthePrussianpeaaremuchbranched。Thetallkindshavelargerleavesthanthedwarfkinds，butnotinstrictproportiontotheirheight:——HAIR’S
DWARFMONMOUTHhasverylargeleaves，andthePOISNAINHATIF，andthemoderatelytallBLUEPRUSSIAN，haveleavesabouttwo—thirdsofthesizeofthetallestkind。IntheDANECROFTtheleafletsarerathersmallandalittlepointed;intheQUEENOFDWARFSratherrounded;andintheQUEENOF
ENGLANDbroadandlarge。Inthesethreepeastheslightdifferencesintheshapeoftheleavesareaccompaniedbyslightdifferencesincolour，inthePOISGEANTSANSPARCHEMIN，whichbearspurpleflowers，theleafletsintheyoungplantareedgedwithred;andinallthepeaswithpurpleflowersthestipulesaremarkedwithred。
Inthedifferentvarieties，one，two，orseveralflowersinasmallcluster，areborneonthesamepeduncle;andthisisadifferencewhichisconsideredofspecificvalueinsomeoftheLeguminosae。Inallthevarietiestheflowerscloselyresembleeachotherexceptincolourandsize。Theyaregenerallywhite，sometimespurple，butthecolourisinconstanteveninthesamevariety。InWARNER’SEMPEROR，whichisatallkind，theflowersarenearlydoublethesizeofthePOISNAINHATIF;butHAIR’SDWARFMONMOUTH，whichhaslargeleaves，likewisehaslargeflowers。
ThecalyxintheVICTORIAMARROWislarge，andinBISHOP’SLONGPODthesepalsarerathernarrow。Innootherkindisthereanydifferenceintheflower。
Thepodsandseeds，whichwithnaturalspeciesaffordsuchconstantcharacters，differgreatlyinthecultivatedvarietiesofthepea;andthesearethevaluable，andconsequentlytheselectedparts。SUGARPEAS，orPOISSANSPARCHEMIN，areremarkablefromtheirthinpods，which，whilstyoung，arecookedandeatenwhole;andinthisgroup，which，accordingtoMr。Gordonincludeselevensub—varieties，itisthepodwhichdiffersmost;
thusLEWIS’SNEGRO—PODDEDPEAhasastraight，broad，smooth，anddark—
purplepod，withthehusknotsothinasintheotherkinds;thepodofanothervarietyisextremelybowed;thatofthePOISGEANTismuchpointedattheextremity;andinthevariety"AGRANDSCOSSES"thepeasareseenthroughthehuskinsoconspicuousamannerthatthepod，especiallywhendry，canhardlyatfirstberecognisedasthatofapea。
Intheordinaryvarietiesthepodsalsodiffermuchinsize;——incolour，thatofWOODFORD’SGREENMARROWbeingbright—greenwhendry，insteadofpalebrown，andthatofthepurple—poddedpeabeingexpressedbyitsname;—
—insmoothness，thatofDANECROFTbeingremarkablyglossy，whereasthatoftheNEPLUSULTRAisrugged;inbeingeithernearlycylindrical，orbroadandflat;——inbeingpointedattheend，asinTHURSTON’SRELIANCE，ormuchtruncated，asintheAMERICANDWARF。IntheAUVERGNEPEAthewholeendofthepodisbowedupwards。IntheQUEENOFTHEDWARFSandinSCIMITARPEAS
thepodisalmostellipticinshape。Iheregivedrawingsofthefourmostdistinctpodsproducedbytheplantscultivatedbyme。
（FIGURE41。PODSANDPEAS。I。QueenofDwarfs。II。AmericanDwarf。III。
Thurston’sReliance。IV。PoisGeantsansparchemin。a。DanO’RourkePea。b。
QueenofDwarfsPea。c。Knight’sTallWhiteMarrow。a。Lewis’sNegroPea。）
Inthepeaitselfwehaveeverytintbetweenalmostpurewhite，brown，yellow，andintensegreen;inthevarietiesoftheSUGARPEASwehavethesesametints，togetherwithredpassingthroughfinepurpleintoadarkchocolatetint。Thesecoloursareeitheruniformordistributedindots，striae，ormoss—likemarks;theydependinsomecasesonthecolourofthecotyledonsseenthroughtheskin，andinothercasesontheoutercoatsofthepeaitself。Inthedifferentvarieties，thepodscontain，accordingtoMr。Gordon，fromelevenortwelvetoonlyfourorfivepeas。Thelargestpeasarenearlytwiceasmuchindiameterasthesmallest;andthelatterarenotalwaysbornebythemostdwarfedkinds。Peasdiffermuchinshape，beingsmoothandspherical，smoothandoblong，nearlyovalintheQUEENOF
THEDWARFS，andnearlycubicalandcrumpledinmanyofthelargerkinds。
Withrespecttothevalueofthedifferencesbetweenthechiefvarieties，itcannotbedoubtedthat，ifoneofthetallSUGAR—PEAS，withpurpleflowers，thin—skinnedpodsofanextraordinaryshape，includinglarge，dark—purplepeas，grewwildbythesideofthelowlyQUEENOFTHEDWARFS，withwhiteflowers，greyish—green，roundedleaves，scimitar—likepods，containingoblong，smooth，pale—colouredpeas，whichbecamematureatadifferentseason:orbythesideofoneofthegiganticsorts，liketheCHAMPIONOFENGLAND，withleavesofgreatsize，pointedpods，andlarge，green，crumpled，almostcubicalpeas，——allthreekindswouldberankedasdistinctspecies。
AndrewKnight（9/85。’Phil。Tract。’1799page196。）hasobservedthatthevarietiesofpeaskeepverytrue，becausetheyarenotcrossedbyinsects。
Asfarasthefactofkeepingtrueisconcerned，IhearfromMr。MastersofCanterbury，wellknownastheoriginatorofseveralnewkinds，thatcertainvarietieshaveremainedconstantforaconsiderabletime，——forinstance，KNIGHT’SBLUEDWARF，whichcameoutabouttheyear1820。（9/86。’Gardener’sMagazine’volume11826page153。）Butthegreaternumberofvarietieshaveasingularlyshortexistence:thusLoudonremarks（9/87。’EncyclopaediaofGardening’page823。）that"sortswhichwerehighlyapprovedin1821，arenow，in1833，nowheretobefound;"andoncomparingthelistsof1833withthoseof1855，Ifindthatnearlyallthevarietieshavechanged。Mr。
Mastersinformsmethatthenatureofthesoilcausessomevarietiestolosetheircharacter。Aswithotherplants，certainvarietiescanbepropagatedtruly，whilstothersshowadeterminedtendencytovary;thustwopeasdifferinginshape，oneroundandtheotherwrinkled，werefoundbyMr。Masterswithinthesamepod，buttheplantsraisedfromthewrinkledkindalwaysevincedastrongtendencytoproduceroundpeas。Mr。Mastersalsoraisedfromaplantofanothervarietyfourdistinctsub—varieties，whichboreblueandround，whiteandround，blueandwrinkled，andwhiteandwrinkledpeas;andalthoughhesowedthesefourvarietiesseparatelyduringseveralsuccessiveyears，eachkindalwaysreproducedallfourkindsmixedtogether！
Withrespecttothevarietiesnotnaturallyintercrossing，Ihaveascertainedthatthepea，whichinthisrespectdiffersfromsomeotherLeguminosae，isperfectlyfertilewithouttheaidofinsects。YetIhaveseenhumble—beeswhilstsuckingthenectardepressthekeel—petals，andbecomesothicklydustedwithpollen，thatitcouldhardlyfailtobeleftonthestigmaofthenextflowerwhichwasvisited。Nevertheless，distinctvarietiesgrowingcloselytogetherrarelycross;andIhavereasontobelievethatthisisduetotheirstigmasbeingprematurelyfertilisedinthiscountrybypollenfromthesameflower。Thehorticulturistswhoraiseseed—peasarethusenabledtoplantdistinctvarietiesclosetogetherwithoutanybadconsequences;anditiscertain，asIhavemyselffound，thattrueseedmaybesavedduringatleastseveralgenerationsunderthesecircumstances。（9/88。SeeDr。Andersontothesameeffectinthe’BathSoc。
AgriculturalPapers’volume4page87。）Mr。Fitchraised，asheinformsme，onevarietyfortwentyyears，anditalwayscametrue，thoughgrownclosetoothervarieties。Fromtheanalogyofkidney—beansIshouldhaveexpected（9/89。Ihavepublishedfulldetailsofexperimentsonthissubjectinthe’Gardener’sChronicle’1857October25。）thatvarietiesthuscircumstancedwouldhaveoccasionallycrossed;andIshallgiveintheeleventhchaptertwocasesofthishavingoccurred，asshown（inamannerhereaftertobeexplained）bythepollenoftheonevarietyhavingacteddirectlyontheseedsoftheother。Whethermanyofthenewvarietieswhichincessantlyappearareduetosuchoccasionalandaccidentalcrosses，Idonotknow。
NordoIknowwhethertheshortexistenceofalmostallthenumerousvarietiesistheresultofmerechangeoffashion，oroftheirhavingaweakconstitution，frombeingtheproductoflong—continuedself—
fertilisation。Itmay，however，benoticedthatseveralofAndrewKnight’svarieties，whichhaveenduredlongerthanmostkinds，wereraisedtowardsthecloseofthelastcenturybyartificialcrosses;someofthem，I
believe，werestillvigorousin1860;butnow，in1865，awriter，speaking（9/90。’Gardener’sChronicle’1865page387。）ofKnight’sfourkindsofmarrows，says，theyhaveacquiredafamoushistory，buttheirgloryhasdeparted。
WithrespecttoBeans（Fabavulgaris），Iwillsaybutlittle。Dr。Alefieldhasgiven（9/91。’Bonplandia’10，1862s。348。）shortdiagnosticcharactersoffortyvarieties。Everyonewhohasseenacollectionmusthavebeenstruckwiththegreatdifferenceinshape，thickness，proportionallengthandbreadth，colour，andsizewhichbeanspresent。WhatacontrastbetweenaWindsorandHorse—bean！Asinthecaseofthepea，ourexistingvarietieswereprecededduringtheBronzeageinSwitzerland（9/92。Heer’DiePflanzenderPfahlbauten’1866s。22。）byapeculiarandnowextinctvarietyproducingverysmallbeans。（9/93。Mr。BenthaminformsmethatinPoitouandtheadjoiningpartsofFrance，varietiesofPhaseolusvulgarisareextremelynumerous，andsodifferentthattheyweredescribedbySaviasdistinctspecies。Mr。Benthambelievesthatallaredescendedfromanunknowneasternspecies。Althoughthevarietiesdiffersogreatlyinstatureandintheirseeds，"thereisaremarkablesamenessintheneglectedcharactersoffoliageandflowers，andespeciallyinthebracteoles，aninsignificantcharacterintheeyesevenofbotanists。"）
POTATO（Solanumtuberosum）。
Thereislittledoubtabouttheparentageofthisplant;forthecultivatedvarietiesdifferextremelylittleingeneralappearancefromthewildspecies，whichcanberecognisedinitsnativelandatthefirstglance。
（9/94。Darwin’JournalofResearches’1845page285。Sabinein’Transact。
Hort。Soc。’volume5page249。）ThevarietiescultivatedinBritainarenumerous;thusLawson（9/95。’SynopsisoftheVegetableProductsofScotland’quotedinWilson’s’BritishFarming’page317。）givesadescriptionof175kinds。Iplantedeighteenkindsinadjoiningrows;theirstemsandleavesdifferedbutlittle，andinseveralcasestherewasasgreatadifferencebetweentheindividualsofthesamevarietyasbetweenthedifferentvarieties。Theflowervariedinsize，andincolourbetweenwhiteandpurple，butinnootherrespect，exceptthatinonekindthesepalsweresomewhatelongated。Onestrangevarietyhasbeendescribedwhichalwaysproducestwosortsofflowers，thefirstdoubleandsterile，thesecondsingleandfertile。（9/96。SirG。Mackenzie，in’Gardener’sChronicle’1845page790。）Thefruitorberriesalsodiffer，butonlyinaslightdegree。（9/97。PutscheundVertuch’VersucheinerMonographiederKartoffeln’1819s。9，15。SeealsoDr。Anderson’RecreationsinAgriculture’volume4page325。）ThevarietiesareliableinverydifferentdegreetotheattackoftheColoradopotato—beetle。（9/98。Walsh’TheAmericanEntomologist’1869page160。AlsoS。Tenney’TheAmericanNaturalist’May1871page171。）
Thetubers，ontheotherhand，presentawonderfulamountofdiversity。
Thisfactaccordswiththeprinciplethatthevaluableandselectedpartsofallcultivatedproductionspresentthegreatestamountofmodification。
Theydiffermuchinsizeandshape，beingglobular，oval，flattened，kidney—like，orcylindrical。OnevarietyfromPeruisdescribed（9/99。
’Gardener’sChronicle’1862page1052。）asbeingquitestraight，andatleastsixinchesinlength，thoughnothickerthanaman’sfinger。Theeyesorbudsdifferinform，position，andcolour。Themannerinwhichthetubersarearrangedontheso—calledrootsorrhizomesisdifferent;thus，inthegurken—kartoffelntheyformapyramidwiththeapexdownwards，andinanothervarietytheyburythemselvesdeepintheground。Therootsthemselvesruneithernearthesurfaceordeepintheground。Thetubersalsodifferinsmoothnessandcolour，beingexternallywhite，red，purple，oralmostblack，andinternallywhite，yellow，oralmostblack。Theydifferinflavourandquality，beingeitherwaxyormealy;intheirperiodofmaturity，andintheircapacityforlongpreservation。
Aswithmanyotherplantswhichhavebeenlongpropagatedbybulbs，tubers，cuttings，etc。，bywhichmeansthesameindividualisexposedduringale...完整阅读请扫描二维码下载丁香书院APP免费看：