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