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Transcript
SeeingtheSourlands: Ferns ByJimAmon Maidenhairfernafteraspringrain Severalyearsago,whenIwaslearningabouttheplantsintheSourlands,Itooka seriesofcourses,eachonadifferentplant.The=irstthingthenaturalistwhowas teachingacourseonfernssaidwas,“Justabouttheprettiestthingyouwilleversee inthewoodsisaMaidenhairfern.”Iagreewithhercompletely.Therearenotmany ofthemintheSourlandsbutseeingoneissomemorablethatIcantellyouwith precisionthelocationofeveryMaidenhairfernIhaveseenonmyperegrinations there. OnegoodreasonforlearningthefernsoftheSourlandsisthattherearenotmany differentspecies.Unlikethehundredsofspeciesofwild=lowersintheSourlands, thereareonlyabout15speciesoffernsthatacarefulobservermight=ind.(Areal expertmight=ind=iveorsixmore.)Allyouhavetodoislearntoidentifyfouror=ive speciestoamazeyourfriends.Ifyoulearnadozen,youwillbeconsideredanexpert andaskedtoleadanaturewalk. Inancienttimesfernswerethoughtofasmagicalbecausetheyreproducedwithout producinga=lower,seedorfruit,whichwastheonlyknowformofplant propagationatthetime.Wenowknowthattheyreproducebyspores,microscopic dotsthatareusuallyfoundinclustersonthebacksofthefernleaves.(Botanists don’tusetheword“leaves”butinsteadrefertotheentiregreen,leafypartofthe fernasa“blade.”The“pinna”isthefullyseparateportionofthebladethatis attachedtothestem—or,inbotanicalterms,the“rachis.”Thesmallestdivisionof theleafypartofaferniscalleda“pinnule.”)Thecharacterandpatternofthese sporepackagesonthebackofapinnuleisoneofthewaystoidentifyfernspecies. The=irstplantstocolonizelandonearthoccurredabout450millionyearsagoand theyweresporeplants.Plantsthat=loweredandreproducedbyseeds=irst appearedabout100millionyearslater.Graduallytheadvantageofseedsover sporesallowedtheseplantstodominateandthegreatforestsoffern-liketreesthat wereoriginallydominantbecamereplacedbyseedbearingplants.Theadvantageof seedsisthattheycomeinacapsulewithahardshellandwithnutrientsinsidethat allowtheseedtobecomeaplant.Seedsalsoarebetteratwithstandingfrost, predationfrominsects,andextremeheat—including=ireinsomecases.Further, theydonothavetolandinawetsitetogerminateand,astheindigestiblepartofa fruit;theyarewidelyspreadbyanimals.Fernsporedonotdirectlyproducefern plants.Theyneedtolandinawetenvironmentandtheretheymightforman intermediateplantcalledagametophyte(aboutaquarterofaninchindiameterso theyareseldomseen).Thegametophytecontainseggsandspermandwhenitis ripetheyarereleased.Ifthehabitatisstillwetthespermswimtotheeggsand fertilizethem.Thefertilizedeggsthenwill,ifhabitatconditionscontinuetoberight, becomeferns.Amaturefernplantwillhaveoversixtymillionsporesandmay produceoneortwonewfernseachyear.Thecomplicationofthisprocessmakesme thinktheancientswereright—fernsaremagicalplants! Ihavehadsomedif=iculty=indingtherolethatfernsplayintheecosystem.Nothing seemstoeatthem—neithermammalsnorinsects.Idonotknowofanythingthat nestsinthem.Theydoshadethegroundandthereforehelpitretainwater,andthey alsocanstabilizesoilonaslope,butotherplantscaneasilycarryoutthosevalues. Whatfernsdoveryimportantlyisaddgreatbeautytothelandscape.Theyare beautifulandthatisenough.
