Deciduousforestsgrowinthewell-balancedregionswheresummerandwinterapproachequality，whereneitherisundulylong，andwhereneitherissubjecttoprolongeddrought。TheyextendsouthwardfromcentralNewEngland，theGreatLakes，andMinnesota，toMississippi，Arkansas，andeasternTexas。TheypredominateeveninpartsofsuchprairieStatesasMichigan，Indiana，southernIllinois，andsoutheasternMissouri。Nopartofthecontinentismorepopulousormoreprogressivethantheregionsoncecoveredbydeciduousforests。IntheUnitedStatesnearlysixtypercentoftheinhabitantsliveinareasreclaimedfromsuchforests。YettheareaoftheforestsislessthanaquarterofthethreemillionsquaremilesthatmakeuptheUnitedStates。
IntheirrelationtohumanlifetheforestsofAmericadifferfarmorethandoeithergrass-landsordeserts。Inthefarnorth，aswehaveseen，thepineforestsfurnishoneoftheleastfavorableenvironments。Inmiddlelatitudesthedeciduousforestsgototheoppositeextremeandfurnishthemosthighlyfavoredofthehomesofman。Stillfarthersouthwardtheincreasingluxurianceoftheforests，especiallyalongtheAtlanticcoast，rendersthemlessandlessfavorabletomankind。InsouthernMexicoandYucatanthestatelyequatorialrainforest，themostexuberantofalltypesofvegetationandthemostunconquerablebyman，makesitsappearance。ItformsadiscontinuousbeltalongtheweteastcoastandonthelowerslopesofthemountainsfromsouthernYucatantoVenezuela。ThenitisinterruptedbythegrasslandsoftheOrinoco，butrevivesagaininstillgreatermagnificenceintheGuianas。ThenceitstretchesnotonlyalongthecoastbutfarintothelittleknowninterioroftheGreatAmazonbasin，whilesouthwarditbordersallthecoastasfarassouthernBrazil。IntheAmazonbasinitreachesitshighestdevelopmentandbecomesthecrowninggloryofthevegetableworld，themostbafflingobstacletohumanprogress。
Exceptinitsevileffectsonman，theequatorialrainforestistheantithesisoftheforestsoftheextremenorth。Theequatorialtreesarehardwoodgiants，broadleaved，brightflowered，andoftenfruit-bearing。Thenortherntreesaresoftwooddwarfs，needle-leaved，flowerless，andcone-bearing。Theequatorialtreesareoftenbranchlessforonehundredfeet，butspreadatthetopintoabroadoverarchingcanopywhichshutsoutthesunperpetually。Thenortherntreesformsharplittlepyramidswithlow，widelyspreadingbranchesatthebaseandonlyshorttwigsatthetop。Intheequatorialforeststhereisalmostnounderbrush。Theanimals，suchasmonkeys，snakes，parrots，andbrilliantinsects，livechieflyintheloftytreetops。Inthenorthernforeststhereisalmostnothingexceptunderbrush，andthefoxes，rabbits，weasels，ptarmigans，andmosquitoesliveclosetothegroundintheshelterofthebranches。Bothforestsarealike，however，inbeingpracticallyuninhabitedbyman。Eachispeopledonlybyprimitivenomadichunterswhostandattheverybottominthescaleofcivilization。
Asidefromtherainforesttherearetwoothertypesintropicalcountries——jungleandscrub。Thedistinctionbetweenrainforest，jungle，andscrubisduetotheamountandtheseasonofrainfall。AnunderstandingofthisdistinctionnotonlyexplainsmanythingsinthepresentconditionofLatinAmericabutalsointhehistoryofpre-ColumbianCentralAmerica。Forests，aswehaveseen，requirethatthegroundbemoistthroughoutpracticallythewholeoftheseasonthatiswarmenoughforgrowth。Sincethewarmseasonlaststhroughouttheyearwithinthetropics，denseforestscomposedofuniformlylargetreescorrespondingtoouroaks，maples，andbeecheswillnotthriveunlessthegroundiswetmostofthetime。Ofcoursetheremaybenorainforafewweeks，buttheremustbenolongandregularlyrecurrentperiodsofdrought。Smallertreesandsuchspeciesasthecocoanutpalmaremuchlessexactingandwillflourishevenifthereisadryperiodofseveralmonths。Stillsmaller，bushyspecieswillthriveevenwhentherainfalllastsonlytwoorthreemonths。
Hencewheretherainyseasonlastsmostoftheyear，rainforestprevails;wheretherainyanddryseasonsdonotdiffergreatlyinlength，tropicaljungleisthedominantgrowth;andwheretherainyseasonisshortandthedryseasonlong，thejungledegeneratesintoscruborbush。