The sperm of an angiosperm is formed by the

During fertilization the male and female gametes: In gymnosperms, pollen germinates directly on the ovule. One is the tube cell, the other will act as a sperm. The megasporangia, called ovules , develop within the ovary. Try to visualize, from cross sections of these fruits, how the carpels and ovules were arranged in the flowers that made these fruits. The tube cell contains a generative cell within it.
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Developmental Biology. 6th edition.

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Pollination and Fertilization

Monoecious plants have both types of imperfect flower on the same plant. The Anther Campbell 6th Ed. The seed coat is a hard protective layer that forms from the integuments of the ovule, and usually has to be opened in some way before the seed can germinate. Each microspore is haploid, and often it will enlarge and separate from the tetrad, becoming sculptured by the deposition of sporopollenin and other substances that will turn into the ornamented surface of the pollen grain. The first and second whorls become sepals and petals , respectively; these organs are sterile. Gametophyte size ranges from three cells in pollen to several million in a "lower plant" such as moss.
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Plant Life: Angiosperm Life Cycle

The primary endosperm nucleus divides to form endosperm. Observe the structure of the strobilus female pine cone and note the megasporophylls and megasporangia. The survivors are relegated to scattered populations in restricted habitats, where they live in the shadows of their successful competitors. Division of the germ cell can occur before or after pollination. These three structures are often termed a pistil or carpel. The development of each of the parts of the plant embryo depends on gradients of the plant hormone, auxin. Gymnosperms have simpler pollination as all transmit their pollen by wind.
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Instead, the pollen is picked up, usually by a flying animal such as a bee, bird or bat the pollinator , and gets transferred from plant to plant as the pollinator looks for nectar , which is a sugary liquid flowers secrete. They seem to lack independent motility as suggested in particular by the important role of the pollen tube cytoskeleton in moving the gametes toward the embryo sac, and the absence of cell motility after isolation from pollen grains or tubes. The Seminoles ate the starchy roots of Zamia pumila , found in southern Florida. The fruit provides nourishment for the seed until it ripens and drops to the ground, where the next stage in the life cycle begins. The gametophytes release sperm to fertilize eggs, and fertilization happens right on top of the gametophyte. Biotic agents such as birds, insects, or mammals or abiotic agents such as wind or water can accomplish this transfer process, known as pollination. Where can we find these trees on campus?
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