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Why can several cycad embryos begin developing in a single seed?
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gymnosperm
Pine cone and exposed seeds of the pinyon pine (Pinus edulis). Pinyon pines are gymnosperms and bear their edible seeds, known as pine nuts, in protective cones instead of fruit.
Several cycad embryos can begin developing in a single seed because cycads produce multiple archegonia within the female gametophyte.1
In most cycad species, a single female gametophyte develops from one to six archegonia, though this number can reach up to 100 in the genus Microcycas. Because each archegonium contains a large egg capable of being fertilized, multiple eggs can be fertilized simultaneously. While this process initially allows several embryos to begin development—a condition known as polyembryony—typically only one embryo reaches maturity, while the others eventually abort.12