. Advanced biology. Biology; Physiology; Reproduction. Complicated nuclear divisions in the embryo sac of the ovule of a plant result in the formation of eight nuclei, of which one is an egg nucleus and two are polar nuclei. The two polar nuclei lie near the center of the cell. The egg nucleus is the female gamete. scattering the pollen. When pollen reaches the stigma of the pistil, it may be caught and held by hairy outgrowths particularly adapted for that purpose. The stigma then secretes certain nutrient materials which the pollen absorbs. After this pollina- tion, the pollen grain germinat
. Advanced biology. Biology; Physiology; Reproduction. Complicated nuclear divisions in the embryo sac of the ovule of a plant result in the formation of eight nuclei, of which one is an egg nucleus and two are polar nuclei. The two polar nuclei lie near the center of the cell. The egg nucleus is the female gamete. scattering the pollen. When pollen reaches the stigma of the pistil, it may be caught and held by hairy outgrowths particularly adapted for that purpose. The stigma then secretes certain nutrient materials which the pollen absorbs. After this pollina- tion, the pollen grain germinates by sending out a slender thread- like tube. The pollen tube grows down through the pistil and penetrates the ovule through an opening called the inicropyle. As it grows, cer- tain nuclear divisions take place, which produce two sperm nuclei. The sperm nuclei with their reduced number of chro- mosomes are the male gametes of the plant. Production of the female A photomicrograph of a part of an ovule show- -n i i • i ing the nuclei in the embryo sac. Compare it gamete. hach OVUlc HI the with the diagram at the top of the page. • p i • ^ i i ovarv IS lormed as the out- growth of a few cells from the ovary wall. One of the cells in the interior of the young ovule appears larger and richer in. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Wheat, Frank Merrill; Fitzpatrick, Elizabeth T. New York ; Boston [etc. ] : American Book Company
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Keywords: ., bookcentury1900, bookdecade1920, booksubje, booksubjectphysiology
