| 11. | Male spores ( microspores ) are extremely small and are produced inside each microsporangium.
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| 12. | These are fertilized by sperm produced by the male gametophyte developing from the microspore.
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| 13. | The microspores become microgametophytes ( pollen ).
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| 14. | The microsporangia produce the microspores, which for seed plants are known as pollen grains.
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| 15. | The plants demonstrate simultaneous microsporogenesis, the microspores are tetrad, tetrahedral, or isobilateral.
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| 16. | These new microspore cells then undergo mitosis and form a tube cell and a generative cell.
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| 17. | In the microgametogenesis, the unicellular microspores undergoes mitosis and develops into mature microgametophytes containing the gametes.
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| 18. | The plants are heterosporous with spores of two different size classes, known as megaspores and microspores.
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| 19. | For example, the pollen grains of flowering plants develop out of microspores produced in the anthers.
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| 20. | Heterosporic plants, as their name suggests, bear spores of two sizes microspores and megaspores.
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