Download Lycopodium

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