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["Kieran &/or Donna" <holycow@frontiernet.net>]

Sorry, it now seems that there are a total of 3 words to describe what hybrid citrus does in it's seeds:  Nucellar, which has to do with the embryo coming from the cell layers of the parent plant, polyembryonic, which usually happens in nucellar seedlings, but not always, and apomictic, which just means asexually.  All are accurate except for the cases in which a single nucellar embryo forms, which is pretty easy to spot because it is seldom as symmetrical as the embryo in a zygotic seed, AND there will be a tiny hollow at the tip of the seed where the zygotic embryo died. 

 

Richard Harrison said:  "I have never noticed polyembriony with Meiwa kumquat seeds that germinated."

 

Ah yes, that is because most of the several embryos are very small and the biggest one wins.  The zygotic embryo does not always abort, but it isn't necessarily big enough to survive.  If you peel the seeds you'll see the extra embryos.  I found the whole subject very interesting because in some cases a white seeded citrus tree will be near a kumquat tree and the white seeds will contain the green cotyledons of a cross to the kumquat.  In such a polyembryonic seed, the tiny green zygotic embryo theoretically could be removed and dropped in a nutrient solution to grow.  Some very interesting crosses could be produced this way.  Of course, it would be easier to do it the other way, hybrid pollen onto Nagami, which is zygotic, or Meiwa pollen onto a mandarin or lemon, or huh, I never thought about it, onto Yuzu.  That I'd like to see.  Yuzu and kumquats both have edible peels, and both very hardy.  Oh, Yuzu probably is pretty sterile, it's a distant cross itself.  Yuzu onto Nagami, though I'd prefer any cross with Meiwa which is much better eating.  I don't know if the Meiwa-Nagami cross that's out there is zygotic or nucellar or has some % of zygotics.   Donna