Hi Vela,
The flowers get all dried up and the seeds are within. The Seed Site has a nice cosmos page.
Remy

Here is a link that might be useful: Cosmos page on the Seed Site

Thanks! That photo helped a lot. I wish they would have shown the underside of the "pod" or whatever they call that casing that the seeds are held in. The tops seem to dry out before the underside. I have some that look dry on top, but the undersides are still green. Do the undersides turn brown too before harvest? Thanks Remy!

Ahh! It's called the head! Just went back and read again! LOL!

Hi vela - the bottom of the "head" ;) will slowly turn kind of a brownish green (mostly brown with a few pale green streaks). But it's best if you let it get as brown as possible to allow for full seed maturity. Patience. It's the ole "a watched pot never boils" philosophy. ;^)

Dave

Thanks again Dave!