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Transcript
GYMNOSPERMS Land Green Plants Liverworts Hornworts Mosses Lycophytes Ferns (including Horsetails) Gnetophytes Cycads Ginkgo Conifers Flowering Plants A Recent Hypothesis Relating to the Phylogeny of Land Green Plants Groups of Gymnosperms • • • • • • • Progymnosperms Cycadeoids Seed ferns Conifers Cycads Ginkgo Gnetophytes Progymnosperms • First trees • Best known example is Archaeopteris • First “real” secondary growth • Reproduced with spores • Upper Devonian until early Carboniferous Archaeopteris Cycadeoids • • • • Cycad-like plants Reached peak in early Mesozoic Bisporangiate reproductive organs Once thought to have given rise to the angiosperms • Two well known fossil genera Cycadeoidea Williamsonia Seed Ferns • • • • • • • Pteridosperms Medullosa is best known example Pinnately compound leaves Concept of form genera Neuropteris for leaves First true seeds Carboniferous as “Age of Ferns” Medullosa Elkinsia polymorpha Conifers • • • • • • • Primitive forms in Carboniferous Transition conifers in early Mesozoic Araucarioxylon fossils in Arizona Peak abundance in mid-Mesozoic Dominant today in some places Only about 630 species Largest and oldest vascular plants Conifers • • • • • • • Most are evergreen All are trees or shrubs Many species are endemic Excurrent growth form Four leaf types Generally adapted for xeric conditions Wood has only tracheids Leaf Types • Needle leaves Pinus and Picea • Linear and flattened Tsuga and Abies • Reduced, scale-like Juniperus • Flat, broad, somewhat angiosperm-like Podocarpus Terminology • • • • • • • • Pollen cones and seed cones Microsporangia Microspores Microgametophyte (= pollen grain) Megasporangia Ovule Megaspores Megasporangia Terminology • • • • • • • • Megagametophyte Ovuliferous scale Micropyle Pollen tube Nucellus Integument Seed coat Embryo Parts of a seed • Seed coat • Endosperm • Embryo • “Wing” in some conifers Cycads • • • • • • • • Palm-like plants Group appeared at least 250 mya Mesozoic is “Age of Cycads” Only about 140 species (perhaps fewer) Zamia native to United States Some large (up to 18 meters) Most very endemic Some live a long time! Ginkgo • • • • • • • Living fossil Only a single species (Ginkgo biloba) Genus has been around since 150 mya Probably does not occur in the wild Often planted in cities Distinctive fan-shaped leaves Dioecious (different individuals) Male tree Female tree Gnetophytes • Three living genera (all very different) Gnetum Ephedra Welwitschia • Total of only about 70 species • Angiosperm-like features • Vessels in xylem Ephedra Microstrobilus Megastrobilus Micropylar tube Megastrobili Microstrobilus with microsporangia Gnetum Welwitschia Questions?
