Jim Bidlack - BIO 1304 GENERAL BOTANY Lecture 36 - Gymnosperms (Part II) IV. Other phyla of gymnosperms A. Phylum Cycadophyta (cycads) 1. Trees palmlike in appearance and very slow-growing 2. Gymnosperms because they produce large cones 3. All modern cycads are dioecious a) Pollen is transferred by a weevil, insects or wind to a droplet of fluid at the micropyle of the ovule b) Pollen grains are carried into the pollen chamber, where they germinate to free swimming sperm 1) Swimming sperm can have 40,000 to 70,000 flagella c) Male gametes are drawn into the archegonium for fertilization d) Uses: food, although some contain neurotoxins that cause convulsions B. Phylum Ginkgophyta (ginkgos) - Ginkgo biloba is the only living species 1. May be the oldest-living seed plant - "living fossil" 2. Used as an ornamental because of its resistance to pathogens and air pollution 3. Fan-like leaves 4. Male and female sporangia are borne on spur shoots on separate plants (dioecious) 5.
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