http://theseedsite.co.uk/db22.html

Use this site. Shows pictures of seeds, organized by latin genus and species.

Here is a link that might be useful: Seed Site

Hi Kim! I grow both Heliopsis Lorraine Sunshine and Summer Sun. The seed is attached to the ends of the petals that ripen at the base. They are chunky arrowheads that are ripened to black when they are ready and they will literally fall out of the head. They look like the black version of echinacea. This is one of those plants that you need to keep an eye on. When they are ready, they will really fall out and the plant re-seeds around its base. Mine are still blooming although summer sun doubles are looking ready to turn.

Thanks for the replies. That seed site from the UK is really wonderful! I also appreciate your description Karen. I think some of my Heliopsis are ready to harvest. They have self-sown the last couple of years so I want to take advantage of getting some seeds. I might have waited too long on the Geum, but I have harvested tons of Tanacetum Niveum. It was pretty easy once the seeds were ripe. Thanks again!