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I was checking some of the seeds I'm germinating, and look! This orange seed is polyembryonic!
Polyembryonic seeds are basically what happens when a plant has twins, and one seed contains more than one embryo. Some plants (like some types of mango) always grow seeds like this. In my experience, it's unusual in oranges though.
Cool, I found a botany paper about this. Apparently, some citrus cultivars have a habit of producing these polyembryonic seeds.
Polyembryony in Citrus
Koltunow et al (1996)
* Open access
http://www.plantphysiol.org/content/plantphysiol/110/2/599.full.pdf
@InvaderXan
Aren't polyembryonic seeds the default for some cultivars, like the navel orange? I thought that was why they had the navel, that it's a separate fruit that never matured grafted onto one that did.
@nosimpleway
Apparently! 