Can't help with portulaca because I don't grow it but the Echinacea seeds are between those black spikes you mentioned. Sorry I have no photo but there's one at the seed site if you click on the link below. The seeds are shaped like tiny space shuttles and are a light tan color. With gloves on, I cut the seedheads off my Echinacea, then hold the stub of stem in a pair of pliers while I use an ice pick to poke the seeds out from between the black spikes.

Here is a link that might be useful: Echinacea seed photo

The soft round things where the flowers used to be on your portulaca are the seed pods. There will be many seeds inside, black when ripe - very small.

Here is a link that might be useful: {{gwi:252785}}

Cool and dry for keeping the seeds. Let them air dry a few days (plate or open container, paper bag), then package, and most rooms in your house would be fine. Just exclude excessive heat or high humidity - like kitchen or bathroom drawer, next to your wood stove ;)

Oh great, thank you for pics and info!I can now clearly see the tan colored Echinacea seeds. I had rubbed them off the flower head, together with the black spikes. It will be a job to separate them... or, since there is plenty, should I start all over ? But how do you poke the seeds out from between the spikes without also getting the spikes ? I don't seem to see well enough...
Re: portulaca, how do you know when the seeds are ripe? Yesterday I had collected several of these soft " buds" and left them in an open paper bag to dry. I just looked again, some of these "buds"are still very soft, when I squeeze them they turn into a mushy mess with nothing remotely like a black seed in sight. However, I can also see some tiny black dots sticking to the inside of the paper bag....obviously some of the buds contained them, but which ones? In other words, what am I looking for that will contain ripe seeds? It's pretty cool and rainy now here in Toronto, the portulaca stopped blooming a while back, I am assuming that the seeds should be ripe now, unless they already fell to the ground?

The ripe pods would be open, they would split if they have spilled their seeds. Look for some intact, and while not completely brown and dry looking, look for those at least more yellow green than green. Open one, see if the seeds inside are black and mature to get an idea of which will have the ripe seeds.

If you are finding them unripe, another way to avoid missing the ripe seeds before they are released from the pod and spilled onto the ground, bag the end with the pod (s). Take a square of nylon stocking and a twist tie, that way you can leave it on the plant ripening until the last possible minute and not risk losing the seeds.

I have a lot of unripe monkshood and turtle head pods right now, I'll be bagging this weekend with the weather getting iffy so I don't lose them in a Fall storm where I'm not paying attention.