I've noticed when collecting seeds from citrus fruits that some have seeds that all have white cotyledons and some have seeds that all have green cotyledons, but that some fruits have a mix. Is that an indication of having at least some zygotic seeds? I'm assuming that the cotyledon color in the seeds is genetic and not environmental since Nagle calls out cotylendon color when describing varieties....true? If so does anyone know if green or white is dominant?
Thanks,
Greg

I thought it was genetic, according to the type(species) but complicated due to hybrids, as nearly all Citrus are some kind of historic hybrid.
Old fruit can have maturing seed with green cotyledons, as the seed begins to shoot inside the fruit. If you exclude this, are you still seeing a mix in the same fruit ?

Absolutely...in fact, I have pictures of some polyembryonic seeds where all the seeds within the same coat have white cotyledons except for one that has green cotyledons. That one with the green cotyledons must be the zygotic seed, while the rest are nucellar clones of the mother plant. Other polyembryonic seeds in the same fruit would have only white cotyledons. The fruit also had some monoembryonic seeds that were all white and others that were just green. None of those seeds were shooting and the fruit was young and nice.

Interesting notice, Greg! It reminds me of an old experiment taught at school: if you cross-pollinate a pea with green, smooth seeds and a variety with yellow, rough seeds, you'll get plants producing green rough seeds, and yellow ones with a smooth surface (and of course some of the hybrids will produce similar seeds to their parents' seeds). So the color of cotyledons is inheritable from both parents.

It would be interesting to check how it works. One could cross a citrus variety with green cotyledons and, for example, a trifoliate orange. Then plant the green and white seeds separately and check if the white seeds produced trifoliate seedlings.