One of the many seeds that I obtained from the seville oranges that Mike/Citrange kindly sent to me a while back is finally starting to grow. I noticed that 2 seedlings are emerging frome one seed.
I always thought that seville seeds were monoembryonic...
This means that at least one of the seedlings must be true to type. Is there an easy way to know which one is true?
I read a couple of times to look for the largest one, but why would especially the largest one be true?

Sour Oranges commonly produces from 75 to 80 per cent of nucellar embryos, and thus requires the elimination of only about 25 per cent of the population to remove the variants. - Mmillet

OK, so how does one know which ones are the variants?

That's one of the great problems with breeding citrus! Unless you are crossing with a variety that has an obviously different characteristic (such as trifoliate leaves), you don't know what you've produced until it fruits. A very long process.

By visual determination. If you only have one sour orange seed, and that seed only produced two seedlings that each one looked different, then it could be difficult to determine which one is, or is not, the nucellar seedling. If both looked identical, than they both probably are nucellar. However if you have numerous seedlings, approximately 75 per cent of them should look identical (nucellar). - Millet