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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
roots
leaf
stem = rhizome
sporophyte
bryophytes seedless vasc plants
• gphyte prominent sphyte prominent• no lignified vasc. tissue xylem w/lignin• poikilohydry homeohydry• roots in sporophyte
• rhizoids in gametophyte• spores for dispersal• water for fertilization
sex in seedless vascular plantshomospory heterospory
one type of sporangium & spore
gametophyte w/archegonia & antheridia
gametophytes develop outside spore wall
some lycophytes,most ferns
megasporangium w/ megaspores (food) --> gphyte w/archegonia
microsporangium w/ microspores (travel) --> gphyte w/antheridia
gametophytes develop inside spore wall
most lycophytes,water ferns
arose several times1st 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