The seeds are a part of the brown/black dome-like center of the flower. They are very tiny (about 1/16th of an inch long) and very difficult to seperate from the chaff. In the link below, the seed is the "fuzzy point" of the dart-like object at the bottom center of the drawing. If you are going to plant them, there's really no need to seperate them from the chaff. Just crumble the "dome" with your thumb and forefinger and spread the seed and chaff mix on your sowing media.

If you are trying to seperate some seed from the chaff for trading purposes, the only way that I've been able to do it is to thoroughly crumble the "dome" on a paper plate and then gently shake the plate to seperate out some seed. The seed is only slightly heavier than the chaff, so it is a long tedious process.

Here is a link that might be useful:

Thanks Wisconson for your very helpful explanation. IN the past, when sowing the tinier seeds,I have often sown the chaff and seed together as I have very poor eyesight, and have never really had germination troubles doing that. Your link was great...thanks again.