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LOWER VASCULAR PLANTS Land Green Plants [“Embryophytes”] Bryophytes Liverworts Hornworts Mosses Vascular Plants Evolutionary Relationships of Land Green Plants Land Plants Plants with Stomata Vascular Plants Plants with Megaphylls “Bryophytes” Mosse s Lycophytes Fern “Allies” Horsetails Seed Plants Algal Charophytes First Vascular Plants • Late Silurian throughout the Devonian • Approximately 425 to 360 million years ago • Bryophyte-like ancestors that first invaded land ca 500 million years ago • Small and simple • BUT tracheids present zoospore meiosis meiosis spores 2n 2n n n Major Groups [Fossil] • Rhyniophytes Trimerophytes Cooksonia Rhynia • Zosterophylls Lycophytes • Trimerophytes Euphyllophytes • Progymnosperms Rhyniophyta • First to appear in fossil record • Dichotomous equal branching of main axis • No differentiation into stem, leaves and root • Homosporous • Gametophyte and sporophyte may have been similar in size • Terminal sporangia Rhynia Cooksonia Gametophyte Zosterophylls • Appear slightly later in the fossil record • Dichotomous branching of main axis but lower branching in different directions • No differentiation into stem, leaves and root (but some had enations) • Larger than rhyniophytes • Homosporous • Laterial sporangia that were dehiscent Sawdonia Sawdonia Zosterophyllum Trimerophytes • Appear even later in the fossil record • Larger and more complex plants than members of the first two groups • Main axis larger than secondary axes • Homosporous • Terminal paired sporangia that were dehiscent • Relatively more vascular tissue Major Groups [Living] • Lycophyte clade • Euphyllophyte clade Ferns [two different groups] Whisk ferns Horsetails Seed plants Stele – central mass of primary vascular tissue (plus other associated tissues) Protostele – solid core of vascular tissue Siphonostele – central cylinder with pith in center Leaf gaps and leaf traces Eustele – complex matrix of discrete strands of vascular tissue around a pith Leaf Types • Microphylls Relatively small Single strand of vascular tissue • Megaphylls Relatively large System of branching strands of vascular tissue Microphyll Megaphyll Eusporangiate Ferns Psilophytes Horsetails No roots or leaves Leptosporangiate Ferns Thin walled sporangia Thinner, delicate gametophytes Big, clunky gametophytes Pteridophyta Rhynia Questions?
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