"Shown here is the underground bisexual reproductive stage of the whisk fern, Psilotum nudum, approximately 1 millimeter long. The rounded male sex organs (colored blue) release thousands of sperm cells into the film of water that surrounds the soil particles. The sperm swim to the smaller female sex organs (pink), each of which contains an egg cell. Only one sperm cell fertilizes each egg, which is housed deep within the plant tissue. Embryos are nourished and protected by the surrounding cells until they elongate and grow out of the soil into the air. Then photosynthesis begins, and the young green plant becomes established and grows into the familiar mature fern."
Plant biologist Karen Renzaglia has been documenting the reproductive phase of early land plants for over 20 years. Her work on plant evolution has been funded by the National Science Foundation.
Scanning electron micrograph by Karen Renzaglia. Color enhancement by Steve Mueller, IMAGE Facility.
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