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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 1 10/20/12 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 2 10/20/12 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 3 10/20/12 Selaginella lepidophylla = resurrection plant dry wet Isoetes = quillwort P? Psilotophyta = whisk ferns Only 2 genera left eg: Psilotum 4 10/20/12 P? Equisetophyta = horsetails, scouring rushes Only 1 genus left: Equisetum Have green, hollow stems Horsetails were once trees (reconstruction of a Devonian swamp) 5 10/20/12 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) 6 10/20/12 Fern life cycle focus on sporophyte (2N) Sorus holds sporangium/ia indusium Megaphyll leaves 7 10/20/12 fiddle-neck = crozier: spiral unfolding of young leaves 8