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10/20/12
Ch 21:
Early Vascular
Plants = nonseed plants
Trends:
sporophyte becomes dominant, gametophyte reduced
spores: homospory - > heterospory
sperm still swim
true plant organs appear
stems first
roots
leaves
microphylls - > megaphylls
vascular tissue: xylem & phloem
Earliest identifiable
fossil vascular plants
P: Rhyniophyta
Dichotomous branching
stems
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P: Lycophyta
Lycopodium = club moss, ground pine/cedar
strobilus
microphylls
Lycopodium
life cycle
(homosporous)
mitosis
2N adult
(underground)
1N adult
mitosis
Lycopods were once trees
(and microphylls were not small)
Carboniferous Period
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http://www.youtube.com/watch?v=F3ChXba3dus
Selaginella = spike moss
Selaginella life
cycle
(heterosporous)
mitosis
mitosis
2N adult
heterosporous
(underground)
mitosis
1N adult
with sperm
1N adult
(underground) mitosis
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Selaginella lepidophylla = resurrection plant
dry
wet
Isoetes = quillwort
P? Psilotophyta = whisk ferns
Only 2 genera left
eg: Psilotum
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P? Equisetophyta = horsetails, scouring rushes
Only 1 genus left: Equisetum
Have green, hollow stems
Horsetails were once trees
(reconstruction of a Devonian swamp)
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P: Polypodiophyta = ferns
Fern life cycle
(usually
homosporous, but a
few species are
heterosporous)
2N adult
mitosis
mitosis
sperm
(above ground)
1N adult
Fern
1N gametophyte = prothallium
(above ground, photosynthetic)
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Fern life cycle
focus on
sporophyte (2N)
Sorus holds
sporangium/ia
indusium
Megaphyll leaves
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fiddle-neck = crozier: spiral unfolding of young leaves
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