Early vascular plants fossil record branched sporophytes dichotomous

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 H 2 O 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 1 st 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