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Early vascular plants (fossil record) • branched sporophytes – dichotomous branching – terminal sporangia • rhizome = horizontal stem • still attached via rhizoids – eventually roots, evolved • stem but no leaves • lignified water conducting cells modern “seedless vascular plants” (grade not clade) • homeohydry; lignified H2O conducting cells • branched sporophytes – dichotomous branching in lycophytes – non-dichotomous branching in ferns – subterminal sporangia • rhizomes & roots • leaves – microphylls (one vein) in lycophytes – megaphylls (branched veins) in ferns – sporophylls leaves that bear sporangia life cycle of seedless vascular plants • gametophyte small, short-lived • sporophyte prominent – specialization for spore dispersal gametophyte leaf sporophyte stem = rhizome roots bryophytes • gphyte prominent • no lignified vasc. tissue • poikilohydry • • • • seedless vasc plants sphyte prominent xylem w/lignin homeohydry roots in sporophyte rhizoids in gametophyte spores for dispersal water for fertilization sex in seedless vascular plants homospory heterospory one type of sporangium & spore megasporangium w/ megaspores (food) --> gphyte w/archegonia gametophyte w/archegonia & antheridia microsporangium w/ microspores (travel) --> gphyte w/antheridia gametophytes develop outside spore wall gametophytes develop inside spore wall some lycophytes, most ferns most lycophytes, water ferns arose several times 1st step in evol of seeds extant seedless vascular plants • 1. lycophytes • Lycopodium and relatives – temperate forest floor, bogs – tropical epiphytes • Selaginella diverse habitats – incl model organism • Isoetes – small, aquatic now; big fossil trees extant seedless vascular plants • 2. Pterophytes (ferns) including: • Psilotum (whisk fern) • Equisetum (horsetail, scouring rush) – big fossil trees • tree ferns, water ferns fossil seedless vascular plants • Carboniferous forests 290-360 mya • fossil fuels (esp. coal) – plants died, didn’t decay (stored C) – global cooling • “coal ball” = rock w/fossil plants – NOT compressed into coal – macrofossils w/fine details preserved