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Gymnosperms - I Gymnosperms Phyla Cycadophyta Ginkgophyta...

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I. Gymnosperms: Phyla Cycadophyta, Ginkgophyta, Coniferophyta, and Gnetophyta a. Distinguishing Features : Exposed seeds borne on scale-like structures called cones (strobili), alternation of generations, heterosporous (two types of spores), gametophytes of gymnosperms are microscopic and completely dependent on the large free living sporophyte. Uses pollination as a means of reproduction. b. Phylum Cycadophyta : Cycads resemble palms because they have un-branched trunks and large, closely packed leaves that are evergreen, sperm is flagellated, seeds are fleshy and exposed to the environment. Sperm are flagellated and motile, but confined within a pollen tube that grows to the vicinity of the egg. c. Phylum Ginkgophyta : Consists of one species: Ginkgo Biloba. A large dioecious tree that does not bear cones. Hardy plants in urban environments that tolerate insects, fungi, and pollutants. Males are usually planted because females produce a smelly and messy fruit. Has not been found in wild and would probably be extinct if not for use in ancient Chinese gardens. Flagellated sperm and motile but
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