Classification of gymnosperms

Classification Of Gymnosperms
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1. Classification Of Gymnosperms David Bierhorst (1971)

2. Outline of Classification followed in the Book Divisions Cycadophyta Ginkgophyta Coniferophyta Gnetophyta

3. Cycadophyta Cycads are vascular, seed plants that are palm-like and are called Sago Palms . The leaves are found in a cluster at the tops of the trunks. Cycads were first to show “ true secondary growth ” along plant’s evolutionary history.

4. Classes Pteridospermopsida Extinct seed ferns. Cycadeoidopsida Fossil members . Cycadopsida Order: Cycadales Genera: Cycas Zamia Microcycas Dioon etc.

5. Ginkgophyta Ginkgophyta is a plant division of “ non-flowering trees ”. Habitat: USA , Canada, China, India, Japan, South Korea, Singapore, Taiwan, Africa, New Zealand, and many other countries…..

6. Class Ginkgopsida Genus: Ginkgo Order: Ginkgoales Family: Ginkgoaceae

7. Coniferophyta It is a largest phylum of “ gymnosperms ”. This is a conspicuous group of woody plants commonly known as the "conifers". The members of this group produce ovules that mature into seeds. These ovules and seeds are found on the upper surfaces of scale structures which often are clustered into " cones ". The Coniferophytes are considered " gymnosperms " (as are the Ginkgophytes) due to the fact that the seeds are exposed in the cone scales rather than being enclosed within an ovary as in the Angiosperms (flowering plants). All conifers are woody plants and many form very large trees. Most conifers are evergreen, however,  Metasequoia glyptostroboides  (see below) is one locally cultivated, non-native example of a conifer that is deciduous

8. Classes Cordaitopsida Comprises of extinct plants and represented by fossils. Coniferopsida 50 genera + 550 species. Trees such as Tsuga(hemlock), Abies(fir), Picea(spruce), Junipers(juniper, red cedar), Sequoiadendron(sierra redwood) etc. Taxopsida Female strobilus is absent & ovules develop at the ends of short lateral branches. Taxus & Torreya are representative genera of class.

9. Gnetophyta

10. Class Gnetopsida Orders: Ephedrales Gnetales Welwitschiales

11. Any Question ?