《木材学(英文)》全套教学课件

全套可编辑PPT课件

Theprogressofhumanityfromtheprimitivestatetothepresentday’shighlyadvancedtechnologyhasbeencloselyassociatedwithdependenceonwood.

Therelativeeaseofworkingitanditsalmostuniversalavailabilityhavemadewoodanessentialmaterialforhumansurvival.Withthedevelopmentoftechnology,woodcametobeusedforboats,vehicles,bridges,andasfuelforsmeltingores

andworkingmetals.

Acomprehensiveknowledgeofthecharacteristicsifanymeterialisessentialtoitsbestutilization.Thisisespeciallytruewithwood.IntroductionAllwood,regardlessofitsbotanicalorigin,possessescertaincharacteristicsincommon.Thesearesummarizedinthefollowingpoints.

1.Woodisanisotropicinnature:i.e.,itexhibitsdifferentphysicalpropertieswhentestedalongitsthreemajordirectionalaxes.

2.Woodisahygroscopicsubstance;i.e.,itlosesandgainsmoistureasaresultofchangesintheatmospherehumidityandtempeture.

3.Woodisbiodegradable.

4.Woodiscombustible.

5.Woodisremarkablyinerttotheactionofmostchemicals.1CharacteristicPropertiesofWood(木材的特性)Woodisaninherentlyvariablesubstancebecauseofitsorigihsaaproductofmetabolismofthelivingtree.Asaresult,itspropertiesaresubjecttowidevariationsbroughtaboutbythephysiologyofthetreesandexternalfactorsaffectingitsgrowth.Therefore,woodcharacteristicsmayvaryindifferentpartsofthesametreeaswellasfromtreetotree.Furthermore,woodisaproductofnotonebutmanyspeciesoftreeswitheachkindofwoodexhibitingitsownanatomical,physical,andchemicalproperties.Inconsequencewehaveavailableamaterialwithanalmostinfiniterangeofpropertiesandcharacteristicsfromwhichtoselectforparticularuserequirements.2VariabilityofWoodProperties(木材性质的变异)

Thesupremacyofwoodasarawmaterialforpulpandpaperisunquestioned.Thereisnoothernaturalsubstancethatcanmeettheever-increasingdemandsofmodernsocietyforpaperanstheotherpulpproducts.

Somemethodsofwoodconversionintochemicals,suchasreductionofwoodwastetoalcohols,havealreadybeendeveloped,andotherpotentialsexistforusingwoodasarawmaterialforproducingchemicalsthatarenowobtainedfrompetroleum.3WoodasanInsuatrialRawMeterial(木材作为工业原料)1.Woodmaybecutandworkedintovariousshapeswiththeaidofsimplehandtoolsorwithpower-drivenmachinery.Itthereforelendsitselfwellnotonlytoconversioninafactorybutalsotoon-the–sitefabrication.

2.Flexuralrigidityinrelationtotheweightofthematerial,isoneoftheoutstandingmechanicalpropertiesofwood.Thehighflexualrigidityofwoodismosteffectiveinmembersinwhichthelengthisfarinexcessofdepthofthecrosssection.4WoodasaConstructionMaterial(木材作为建筑材料)3.

Woodstructurescanbedesignedtocarryimpactloadsthataretwiceasgreatasthosretheycansustainunderstasticloading.Thiscancontrastedwithsteelandconcreteforwhichnoincreaseinloadsisallowedundersimilarconditions.Theexceptionalimpactstrengthofwoodgivesitaconsiderablemechanicalandeconomicadvantageforstucturesdesignedtiresistearthquakesorfousituationswhereabruptloadsareimposed.

4.

Dimensionalchangesthatmaytakeplaceasaresultofriseintemperaturearelesssignificantinwoodconstructionthantheyareinconstructionutilizingmetalstructualmembers.

Chapter2

TheTreeStem(树干)

1ThePlantOriginofWood(木材的植物起源)

Woodisofplantorigin.Notallplants,however,possesswoodystems,andnotallthatdopessesswoodystemsproducetimbersuitableforuseasanindustrialmaterial.Thefollowingcriteriaservetodistinguishwoodyfromnonwoodyplants:

1.Woodyplantsmustbevascularplants(维管植物);i.e.,theymustpossessspecializedconductingtissuesconsistingofxylem(木质部)andphloem(韧皮部).

2.Theymustbeperennialplants(多年生植物);i.e.,theymustliveforanumberodyears.

3.Theymustpossessastemthatpersistsfromyeartoyear.Manyperennialsfailtobeclassedaswoodyplantsbecausetheirstemsdiebacktothegroundeacnhautumn.therootspersistingthroughthewinteransproducinganewstemthefollowingspring.

4.Typicalwoodyplants(模式木本植物),whichincludeallthecommerciallyimportanttimbertrees,exhibitsecondarythicking(次生加厚);i.e.,theyhaveameansofthickeningtheirstemsbysubsequentgrowthindiameter,nottraceabletoterminalgrowingpoints（顶端生长点）.

Thekindsofwoodyplantsmaybedefinedasfollows:

1.Atree(树木)isawoodyplantthatattainsaheightofatleast20feetatmaturityinagivenlocalityandusually(notalways)hasasingleselfsupportingstemortrunk.

2.Ashrub(灌木)isawoodyplantthatseldomexceeds20feetinheightinagivenlocalityandusually(notalways)hasanumberodfstems.

3.Awoodyliana(木质藤本植物)isaclimbingwoodyvine.Woodylianasclimbbytwining,clambering,aerialroots,tendrils,etc.,andarecharacteristicfeaturesoftropicalrainforestsinmanypartsoftheworld.1.1KindsofWoodyPlants(木本植物的种类)Woodsbecomecommerciallyimportantthroughrigorousselectionbasedonthesizeofthetreespeciesproducingthem,thequalityofthewood,theaccessibilityandvolumeofthestandsofagivenkindoftimber,thestatusoftechnologicaldevelopmentofconsumingindustries,andtheprevailingeconomicconditions.1.2FactorsControllingtheDesignationodfWoodasCommerciallyImportant(决定商业上重要木材的因子)Thebodyofallvascularplantsconsistsofacylindricalaxisbearinglateralappendages.Theaxis,inturn,ismadeupoftwostructuallyandfunctionallydistinctparts:thestemandtheroot.

Thestem(树干),alsocalledtrunk(茎)orbole(杆),isanaerialportionoftheaxis;itsupports,successively,limbs,branches,andbranchlets,ofteninamannercharacteristicofthegiventreespecies.Thestemprovidesmechanicalsupportforthecrown,servesasanavenueforconductionbetweenthecrownandtheroots,andonoccasionstoresappreciableamountsofreservefoodmaterials.2TheStem(树干)

Theaxisofatreeisformedthroughtheprocessofelongationandthroughgrowthindiameter.Elongationoftreestemsistraceabletotheprimarygrowth,whichtakesplaceatorneartheapicalgrowingpoints(顶端生长点).Theprimarygrowthisresponsiblefortheelongationnotonlyofthemainstembutalsoofitsbranches,andhenceitcontrolstheultimateheightofthetreeandalsotoalargeextenttheformassumedbythematureplant.Theplanttissuesarisingfromtheapicalgrowingpointsarecalledtheprimarytissues

(初生组织).

2.1FormationoftheStem(树干的形成)

Growthinthediameter(直径生长)isduetotheactivitiesofthevasularwoodcambium(形成层),agrowinglayersituatedbetweenthephloemandthexylem.Growthproducedbythecambiumisdesignatedasthesecondarygrowth(次生生长)orthesecondarythickening(次生加厚),todifferentiateitfromgrowthinlength()traceabletotheapicalgrowingpoints.Plantstissuesoriginatingthtoughcellformationinthevascularcambiumareknownassecondarytissues(次生组织).2.1FormationoftheStem(树干的形成)2.2.1GrowthIncrements(生长量)

Growthincreasementsstandoutinwoodtovaringdegreesbecausethegrowthintensity,andconsequentlythecellsizeandarrangementandthedensityofthewoodproduced,arenotuniformthoroughoutthegrowingperiod.

2.2GrossCharacteristicsofStemWood(树干宏观特性)

1.EarlyandLatewood(早材和晚材)Whenindividualgrowthincrementsoftemperature–zonewoodsareexamined,itisgenerallyapparentthattheportionformedintheearlypartofthegrowingseasonhasalargercellsansisrelativelylowerindensitythanthatformedlaterintheseason;thispartoftheincreasmentiscalledearlywoodorspringwood(早材或春材).Thedenserandusallydarker-coloredwoodformedinthelastpartofthegrowintgseasoniscalledlatewoodorsummerwood(晚材或夏材).

Inveryoldorsuppressedtrees,someofthegrowthincreasementsmaybeinterrupted;i.e.,theydonotcompletelysurrouondthestembutarepresentinpartofit.Suchincrementsarecalleddiscontinuousrings(不连续年轮).

Falseringsoftenleadtoanoverestimateoftreeage.Abandofwhatappearstobelatewoodisformedwhichstimulatesnormallatewoodinappearanceanddensity;thisisfollowedbytissueresemblingearlywood,afterwhichtruelatewoodisproduced.2.DiscontinuousandFalseRings(不连续年轮和假年轮)2.2.2PlanesofReferenceintheStem

Becauseofthemannerofthetreegrowthandthearrangementofwoodcellswithinthestem,threeprincipalplanesarerecognizedinwhichwoodiscustomarilyexamined.Theseplanes,orsurfaces,aretransverse(x)(横截的)，radial(r)（径切的）,andtangential(t)（弦切的）2.2.3SapwoodandHeartwood

Thepartofthewoodycoreinthetreeinwhichsomexylemcellsarelivingandhencephysiologiacllyactiveiscalledsapwood.Afteranindefinitelengthoftime,whichwariesgreatlyindifferentkindsoftreesandwiththeconditionoftheirgrowth,thepthtoplasmofthexylemdies.Secondarychangesthattakeplaceasaresultofthisleadtoformationofaphysiologicallydeadpartofthexylem,calledheartwood.

Chapter3

OriginandDevelopmentof

WoodyCells

(木质细胞的起源和发育)

1ApicalMeristem(顶端分生组织)

Theelongationoftreestems,aswellasthatofthebranchesandroots,istraceabletoprimarymeristems,alsoknownasapicalmeristemsorgrowingpoints(生长点).Theseprimarymeristemsconsistofcellswhicharecapableofrepeateddivisiontoperpetuatethemselvesandformnewtissues.

Figure1depictsschematically,andingreatlysimplifiedform,thecompositesequenceofthedevelopmentoftheprimaryandsecondarytissuesoriginatingfromthedivisionofcellsintheapicalgrowingpoint.2VascularCambium(维管形成层)

Theincreaseindiamaterandthreresultingexpansionincircumferenceoftheplantisaccomplishedmainlybycelldivisioninthevascularcambium

(维管形成层).

Inthethree-dimensionalviewthevascularcambiumisasheathofmeristematiccells,calledcambialinitials,situatedbetweenthesecondaryxylemandthesecondaryphloem;itextendsfromthegrowingtipsinthestemandthebranchesintothecorrespondingregionsintheroots.

Thevascularcambiumiscomposedoffusiforminitials(纺锤状原始细胞)andcambialrayinitials(形成层射线原始细胞).

2.1FormationofNewFusiformInitials

ThemannerinwhichthenumberofthefusiforminitialsinthevascularcambiumisincreasedisillustratedinFig.2-10.Figure2-10Diagramsillustratintthemannerinwhichtheincreaseinthegirthofthecambiumproceedsinnonstratifiedandinstratifiedcambia.

(a)to(c)Fusiforminitialfromanonstratifiedcambium,dividingpseudotransversely;thedaughtercellsresultingfromthedivisionelongateandslidebyoneanotherinthetangentialplane.

(d)to(e)Fusiforminitialsformedbyulateraldivision,inwhichthecellplatecurves,intersectingonlyonesideoftheparentcell.(f)to(h)Fusiforminitialsfromastratifiedcambium;thecellsresultingfromtheradial-longitudinaldivisionexpandlaterallybutdonotelongate.Schematicdrawingshowinglossofacambialfusiforminitialandformationofnewrayinitialsinthecambium.

(a)Initialawithextensiveraycontactsurvives,whileinitialbwithaparseraycontactmaturesintoadeformedcellanddisappears.

(b)Arayissplitbyinstrusivegrowthofafusiforminitial.

(c)Anewrayinitialarisingfrompinchingoffthetopofafusiforminitial.

(d)Twosingleraycellsareformedthroughreductionofashortfusiforminitial;eitherorbothofthesecellsmaysurviveandlaterdevelopintoraysconsistingofanumberofcellsformedbysubsequentdivisionoftheseinitials,ortheymaybeeliminated.2.2FormationofRayInitialsintheVascularCambium(维管形成层内射线原始细胞的形成)Theadditionofnewcellstothexylemandphloem,withtheresultantincreaseinstemdiameter,isaccomplishedbythetangential-longitudinal(periclinal)division(平周分裂)ofthecambialinitials.2.3FormationofNewXylemandPhloemCells(木质部和韧皮部新细胞的形成)(e)Anewrayisformedbyseptationoftheentireshortfusiforminitial.

(f)Anewrayinitialformedonthesideofafusiforminitial,whichwillcontinuetofunctionassuch

Chapter4

TheWoodyCellWall(木质细胞壁)1ChemicalComponentsofthePlantCellWall(植物细胞壁的化学组成)

Woodtissueiscomposedprincipallyofagroupofpolymersubstancesthatmakeupthebulkofthecellwalls.Besides,someextraneousmaterialmaybepresentintheadmixturewiththewallpolymersinthecellwallsorinthecelllumens.

1.1polysaccharideFractionsoftheCellWall(细胞壁的多糖部分)1.1.1Cellulose(纤维素)

Celluloseistheframesubstance(骨架物质)ofthewoodycellwall.Celluloseinwoodycellwallsoccursinacrystallineform.

Modelof

aportionofacellulosemoleculeconsistingoffourgluseunitsjoinedthroughtheir1-4carbonatoms.

1.1.2Hemicellulose(半纤维素)

Hemicelluloseisthematrixsubstance(基体物质)ofthewoodycellwall.

1.2Lignin(木质素)

Linginistheencrustingsubstance(结壳物质)ofthewoodycellwall.LigninisacharacteristicfractionofthewoodycellwallandisformedonlyinthewallsoflivingplantsintheSpermatophytes(种子植物),thePteridophytes(蕨类植物),andthemosses(藓类植物).

Characteristicformsofphenylpropaneunitsoccurringinligninextractedfromthewood.

1.3.1ExtraneousMaterials(次要抽提物质)

Thesesbustances,calledextractives,maybeinfiltratedcompletelyintothecellwallsortheymayoccurassurfacedepositsorplugsincelllumina.1.3SecondaryCellWallComponents(细胞壁次要成分)1.3.2AshContent(灰分含量)

Thealkalineearths,i.e.,calcium,potassium,andmagnesium,usuallyaccountfor70percentofthetotalashpresent.

2BasicStructureoftheWoodyCellWall(木质细胞壁的基本结构)

2.1TheMicrofibil(微纤丝)

Thepolysaccharidesinwoodyplantcellwallsarephysicallyaggregatedintoverylongstrandsknownasmicrofibrils(微纤丝).

Themicrofibilsarearrangedinsheetsthatlie

paralleltothewallsurface.BundlesofmicrofibilsinthesecondarywallofDouglas-fir〔Pseudotsugamenziesii

(Mirb.)Franco〕(北美黄杉).(35,800X)Aggregatesofelementaryfibilsareclassedasmicrofibils.Elementaryfibils(基本纤丝)arepresumablythecellulosicstrandsofsmallestpossiblediameter.Anelementaryfibrilofthiscross-sectionaldimensioncouldcontainaboout40cellulosechains.Electronmicrograph.negativecontrasttechnique,ofelementaryfibrilsofcellulosefromonionrootcellwalls.Elementarydiameter35Angstromunits.(85,500X)Elementaryfibrilscontainstwoarea-amorphousarea(非结晶区)andcrystallinearea(结晶区).Inthecrystallinearea,cellulosemoleculeslieparallel,whileintheamorphousarea,cellulosemoleculesarenotperfectlyaligned.2.2TheStructureofCellWall（壁层结构)

Thewoodcellwallconsistsofprimarywallandsecondary-wall.

Layeringofamaturecellwall.Actually,thesecondarywallconsistsofthreelayers:athinouterlayer;athickcentrallayer;andathininner.ThesethreelayershavecometobedesignatedbytheletterofS.UndertheterminologytheouterlayerislabledasS1.thecentrallayerasS2,andtheinneroneasS3.S2playsanimportantroleinthephysicalnatureofthewood.

Modelofaportionofaconifertracheidwiththewallscutawaytoshowthehelicalorganizationofthemicrofibrilsinthesecondarywall.

2.3DistributionodfChemicalConstituentsintheCellWall(细胞壁化学成分的分布)

Thechemicalcomponentsofthecellwallarenotdistributedthroughoutthecellwall.3ModificationsoftheCellWall(细胞壁的变异)

3.1PittingoftheCellWall(细胞壁的纹孔式)1.pit(纹孔)Apit

isdefinedasarecessinthesecondarywallofthecell,opentothelumenononesideandincludingthemembraneclosingtherecessontheotherside.Normallytwocomplementarypitsinadjacentcellsoccurasapitpair(纹孔对).typesofpitpairsinwood

Simplepitpairsandhalf-borderedpitpairs2.Cellwallpittingcanassumeawidevarietyofforms.Ingeneral,however,thesecanbereducedtothreetypesonthebasisoftheshapeofthepitcavity--simplepit（单纹孔）,borderedpit（具缘纹孔）andhalf-borderedpit(半具缘纹孔).

3.ThestructureofpittingSimplepitting

4.Thedifferenceofsoftwoodandhardwood‘spitting

(1)membranes:Normally,hardwooddoesn’thaveatorus

(2)pitborder.Hardwood‘spitborderisshorter.

Softwood’smembranesHardwood’smembrannesSoftwood‘sbordedpitsBorderdpitpairsHardwood’sborderedpitpairs5.AspiratedPit(闭塞纹孔)

Thesupportingstrandsinthemargooftheclosingmembraneareflexiableandallowtherigidtorustobedisplacedlaterallybysurfacetensionafgainstoneortheotheroftheapertures,toformanaspiratedpit(闭塞纹孔).aspiratedpitaspiratedpitTypesofvesselperforationplates3.2PerforationoftheCellWall(细胞壁的穿孔)

Themajorliquidconductioninhardwoodsisthroughvessels,whicharisebytheformationofopenings,calledperforations(穿孔),inthecommon-endwallsofadjacentvesselelements.

3.3ThickeningsoftheCellWall(细胞壁的加厚)

3.3.1SpiralThickenings(螺纹加厚)

Thesemaydevelopontheinnerface

oftheS3layerintracheidsofalimited

numberofsoftwoods.3.3.2Dentations(锯齿状加厚)

Dentationsintheraytracheidsofthehardpinesarelocalizedwallthickeningswhichappeartoothlike(denate)intheusualmicroscopepreparation.3.4WartStructuresandVesturedPitting(瘤状结构和附物纹孔)

3.4.1Warts(瘤)

Smallwartlikeprotuberancesareoftenevidentandcloselyassociatedwiththecytoplamicremains;thisformationisknownasthewartylayer(瘤).3.4.2Vestured(附物纹孔式)

PittingIntheangiospermsadevelopmentofthewartystructureintolargesimpleofrbranchedformsassociatedwiththepitsisknownasvesturedpitting(附物纹孔式).

4SpecialFormsofCellWalls(细胞壁的特殊形态)

4.1Septa(隔膜)

Anunusualformofcellwallcalledaseptum(隔膜)formsinthefibersofsomehardwoodsafterthesecondarywallhasformedandlignifiedbutwhilethecytoplasmisstillliving.

4.2Tyloses(侵填体)

Inthehardwoods,specializedstructuresmaybeproductedinthevesselsintheprocessoftheheartwoodformation.Thesearebubble-likeoutgrowthsoftheparenchymacellsadjacenttothevesselsandarecalledtyloses(侵填体).

Chapter5

TheMinuteStructureofConiferousWoods(Softwoods)

(针叶树材的微观结构)

Onlytwotypesofcellsshowninfig4-1occurinallsoftwoods:longitudinaltracheids(轴向管胞),whichconstituteover90percentofthevolumeofsoftwoods,andrayparenchymacells(射线薄壁细胞).1LongitudinalConiferousTracheids(针叶树材的轴向管胞)

Thelongitudinalconiferoustracheidsarerelativelylong(3.0to5.0millimeters),four-tosix-sided,prismaticcellswithclosedends.

1.1TracheidVolume(管胞体积)

Theproportionofvolumeofwoodoccupiedbytracheidsindifferentsoftwoodsspeciesvariesonlyfrom90to94percent.1.2ArrangementandShapeofTracheidswithinGrowthRings(生长轮内管保的排列和形态)Theregulararrangementoftherelativelyuniformlongitudinaltracheidsinradialrows,asseenintransversesections,isacharacteristicfeatureofsoftwoods.

Intheearlywoodthelongitudinaltracheidsarehexagonalincrosssection,withthelargerdiameterusuallyintheradiacldirection,..Inthelatewoodthecrosssectionsofthetracheidsareessentiallyrectangular,andflattenedradiallytoatabularshape.Theradialdiameterofatracheidvariesaccordingtoitspositioninthegrowthincrement.

Thetangentialdiameterofalongitudinaltracheidvariesaccordingtotheplacewithinitslengthwherethemeasurementistaken,thepositioninthetree,andfinally,accordingtothekindofwood.

1.3sizeofLongitudinalTracheids

1.4MarkingsoflongitudinalTracheids(轴向管胞的特征)1.4.1Pits(纹孔)

Thepitsinthelongitudinaltracheidsfallintothreecategories:(1)thosebelongingtopitpairsbetweentheadjacentlongitudinaltracheids,andtheyareborderedpits;(2).thosethatareapartofpitpairsprovidingcommunicationbetweenthelongitudinaltracheidandrayparenchymacellsincontactwithit,andtheyarealsoborderedpits.(3)thosethatbelongtopitpairsthatconnectthelongitudinaltracheidswiththeraytracheids,whentheyarepresentintheray.Andtheyaresinglepitsorhalf–borderedpits.

Nearlyallpitsareontheradialwalls,onlyfeworevennopitslocateonthetangentialwallsoflongitudinaltracheids.

Theborderedpitsontheradialwalloftracheidsareboundedaboveandbelowbyzonesofdarkersubstances.Thesestructures,formerlycalledbarsofSanio(萨氏条),arenowknownascrassulae(眉条)1.4.2SpiralThickeningsontheWalloflongitudinalTracheids(轴向管胞壁上的螺纹加厚)Spiralthickenings（螺纹加厚）arepresentasaconstantfeayureinthelongitudianlandraytracheidsinDouglas-fir(),Pacificyew(),andTorreyspp.().Theymayalsooccasionallyoccurinotherwoods,notablyintheraytracheidsandinthelongitudinaltracheidsinthejuvenilewoodofthesprucesandinthelate-woodtracheidsintamarackandinsomehardpines.

1.4.3Callitrisoid

Thickenings(澳柏型加厚)

ThesestructuresarelocalthickeningsofthecellwallthataretypicalofthegenusCallitris(澳柏属),aconiferwhichoccursmostlyinAustralia．1.4.4TrabeculaeinlongitudinalConiferousTracheids（针叶树材轴向管胞上的径列条)

ATrabeculae(径列条)isabarlikestructureextendingacrossthelumenofatracheidfromonetangentialwalltoanother.

1.4.5LongitudinalStrandTracheids(轴向索状管胞)

Thetermstrandtracheidsisappliedtotheshortcellsarrangedinthelongitudinalstringsorstrands.Thesecellsdifferfromthelongitudinaltracheidsinbeingshorterandinpossessingendwalls,oneorbothofwhichareatrightanglestothelongitudianlwalls.2ParenchymainConiferousWoods(针叶树材薄壁组织)

Therearethreetypesofparenchymainsoftwoods,viz.,longitudinalparenchyma(alsocalledaxialparenchyma)(纵向薄壁组织，也称轴向薄壁组织),epithelialparenchyma(泌脂薄壁组织),andrayparenchyma(射线薄壁组织).2.1LongitudinalParenchyma(纵向薄壁组织)

Longitudinalparenchymaisneverabundantinsoftwoods,itmaybequiteconspicuousbecauseofthepresenceofdark-coloredinclusionsinmanyofthecells.

Thelongitudinalparenchymainsoftwoodsoccursintheformofstrandsextendingalongthegrain.Pitsinthecrosswallofaxialparenchymawhenpresentareinvariablysimple.Whenviewesinthelongitudinal

sections,simplepitsgivetheappearanceofbeadlikethickeningsonthetransversewallsofparenchymacells.2.2RayParenchyma(射线薄壁组织)

Rayparenchymacellsarediscusedindetailinthesectiononrays.

2.3EpithelialParenchyma(泌脂薄壁组织)andResinCanals(树脂道)

Theepithelialcellsareexcreting,thin-walledparenchymacellswhichsurroundlongitudinalandtransverseresincanals.

Beacuseofthefluidpressurefromtheresinproducedbytheepithelialcells,thetruemiddlelamellabetweencellsnearthecenteroftheclustersplits,andanintercellularcavitycalledaresincanal(树脂道)isformed.Resincanalsinsoftwoodsareoftwokinds,thosethatarenormalinthewood(正常树脂道)andthatpresumablyariseasaresultofwoundingandarethereforetermedtraumatic(创伤树脂道).

1.Normalresigncanals(正常树脂道)

NormalresigncanalsareaconstantfeatureinPinus,Picea,LarixandPseudotsuga.Normalcanalsoccurinbothlongitudinalandtransversedirectionsinwood.

Normalresincanalsvaryinsizenotonlyaccordingtowhethertheyarelongitudinalortransversebutalsoaccordingtothegenusandsometimesthespecies.Inagivenwood,thelongitudinalresincanalsareinvaricalylargerthanthoseofthetransversetype.

2.TraumaticResinCanals(创伤树脂道).Traumaticresincanals,i.e.,canalspresumablyarisingasaresultofinjury,mayaccompanytransversecanalsofthenormaltype.

Thelongitudinaltraumaticresincanalsaregenerallyarrangedinatangentialrow.

Longitudinalandtransversetraumaticcanalsusuallydonotoccurinthesamesample.Exceptionsdooccur,asisthecasewithdeodar[Cedrusdeodara(Roxb.exLamb.)G.don](雪松)Thetraumatictransversecanals,likethenormaltransversekind,areconfinedtothewoodrays.3TransverselyOrientedCells(横向排列的细

胞)

3.1TypesofTransverseCellsinSoftwoods(针叶树材横向细胞的种类)

TherearethreekindsofTransverseCellsinSoftwoods,allofwhichareincludedintherays:(1)rayparenchymacells,(2)raytracheids,and(3)epithelialcells.

3.1.1RayParenchyma(射线薄壁组织细胞)

Thecellsofrayparenchymaarethin-walledandasallparenchymainthesoftwoods,theyhavesimplepits.Thecommon-wallareasbetweencellsoftherayparenchymaandthelongitudinaltracheidsarecalledcrossfields.

Phillipshasdescribedthefivefairlyweii-definedtypesofcrossfieldpitsinconifersasgiveninthefollowingsection.1.window-likepit(窗格状)2.piceoidpit

（云杉型）3.cupressoidpit(柏型)

4.taxodioidpit（杉型）5.pinoidpit

（松型）3.1.2RayTracheids(射线管胞)

Raytracheidsaretransverselyorientedcellsfoundinsomesoftwoods.Theyareprovidedwithbordedpitsofthesamegeneraltypeasthosefoundinthelongitudinaltrancheids,onlysmaller.3.2RaysinSoftwoods(针叶树材的射线)

Thewood-orxylaryinsoftwoodsconsist

entirelyoftransverselyorientedcells

whicharearrangedinribbon-like

structuresextendingsradiallyinthetreestem.

Coniferouswoodsmayhaveeither

oneortwotypesofrays:(1)rayswithout

resincanalsand(2)rayswithnormal

transverseresincanals.

Chapter6

TheMinuteStructureofConiferousWoods(Hardwoods)

(阔叶树材的微观结构)

Theanatomicalfeaturesthatdistinguishhardwoodsfromconiferouswoodsmaybesummarizedasfollows:

1.Hardwoodsdifferfromsoftwoodsinpossessingvesselelements(导管),whichwhenviewedinthetransversesectionarecalledporse,hencethenameporouswoods(有孔材).Softwoodsaresidtobenonporousinthesensethattheydonotcontaidnvessels(无孔材).

2.Theradialalignmentofthelongitudinalcellsthatcharacterizessoftwoods,whenviewedin