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1、divisionPTERIDOPHYTA***Jim:vol.49Vascularherbs,rarelyarborescent,oftenrhizomatous,oftenwithscales;truerootsusuallypresent(rhizoidsinPsilotum).Leaveseitherbract-likeorafrondwhichiscircinateinbud(exceptinPs
2、ilotaceae,Lycopodiaceae,SelaginellaceaeandOphioglossaceae).Stipeusuallylackingstipules(fleshystipulesinMarattiaceae,non-fleshyonesinOsmundaceae).Laminabroad,simpleorvariouslypinnate,bearingsporangia.Sporangiausuallyinsori(oftenprotectedbyanindusium)orgroupedi
3、nsynangia,or(inPsilotum)borneonthestems.Sporesgerminatingtoproduceaprothalluswhichbearsthemaleandfemaleorgans,producing,afterfertilisation,thenewsporophyte.Thefernsandfernalliesarealargeandancient,worldwidedivisionoflandplants(veryr
4、arely,floatingaquatics).Theyproducespores,usuallyinsori,whichongerminationdevelopintothesexualgenerationcalledtheprothallus,whichbearsthemaleandfemalereproductiveorgans.Wellknowninthefossilstate,especiallyfromtheCarboniferousAge,thegroupconsistsoffourClasses,
5、Psilopsida,Lycopsida,SphenopsidaandFilicopsida,allexceptthethirdoccurringonNorfolkandLordHoweIslands.familyPSILOTACEAEP.S.GreenRoyalBotanicGardens,
6、Kew,Richmond,Surrey,TW93AB,EnglandEpiphytic,lithophyticorterrestrial;rhizomesdichotomouslybranched,bearingrhizoids.Aerialstemssimple,forkedonceordichotomouslybranchedinupperpart,bearingflattened'leaves'orscale
7、-likeappendages.Synangia2-or3-lobed,homosporous.Atropicalorsubtropicalfamilycontainingonlythefollowing2livinggenera,andc.12species;bothgeneranativeontheIslands.R.E.G.PichiSermolli,TentatemPteridophytoru
8、mgeneraintaxonomicumordinemredigendi,Webbia31:313–512(1977);R.A.White,D.W.Bierhorst,P.G.Gensel,D.R.Kaplan&W.H.WagnerJr,TaxonomicandmorphologicalrelationshipsofthePsilotaceae,Bri
