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# Reproduction ## Formation of Embryo Sacs Pistils are composed of stigmas, styles, and ovaries containing one or more ovules. Within the ovule, a cell undergoes meiosis, producing four haploid cells. One of these cells undergoes three more maturation divisions to form the embryo sac, which contai...

# Reproduction ## Formation of Embryo Sacs Pistils are composed of stigmas, styles, and ovaries containing one or more ovules. Within the ovule, a cell undergoes meiosis, producing four haploid cells. One of these cells undergoes three more maturation divisions to form the embryo sac, which contains the egg cell and polar nuclei. ## 5.2.3 Pollination Before fertilization, pollen grains must be transported to the pistil's stigmas. Flower evolution is largely driven by this process of pollination. **Direct Pollination:** Occurs when pollen grains from a flower land on the stigma of a flower on the same plant. This is common in self-pollinating plants. In this case, the resulting plants tend to be less diverse, and there is a higher risk of degradation. Agents of direct pollination include: * **Wind:** Wind carries pollen randomly to any stigma, including those on the same plant. * **Gravity:** Pollen grains fall directly onto stigmas located below the stamens (pollen-producing parts of the flower). **Indirect Pollination:** Occurs when pollen grains from one plant travel to the stigma of a different plant.