1. A large, round cell in plants and algae that develops into an embryo after fertilization by a male gamete; a female reproductive cell in certain organisms.
Usage: biology; botany; technical term

Examples

• The oosphere in the archegonium of a fern is fertilized by sperm cells.
• In algae, the oosphere is protected within a specialized structure called the oogonium.
• The development of the oosphere into an embryo marks the beginning of sexual reproduction in plants.
• Botanists study the oosphere to understand the reproductive cycles of lower plants.
• The oosphere accumulates nutrients and cytoplasm before fertilization occurs.