Carolyn,
I am SUPER impressed you got them to grow from seed!!!

I guess I will try again.
I am ashamed to admit I do not know about the seed pods either. Ask me anything else about purslane and I can tell you! I know it self sows a little because it always came up again in patches when the weather grew warmer. Those seeds are teeny!
So now I wonder if we harvest the day old blooms when they dry up and maybe there is a seed in there! Those seeds are teeny! Maybe I will try that tonight and see what might be there after they dry up.
I did keep a purslane plant in a sunny window one winter. It even bloomed a little in the house. Eventually it stopped blooming...too cold I guess. And I clipped it back to about a1/2 inch from the soil. I watered it every once in a while, just a little. When spring came and the frost was past, I took it back outside and by June it was full and lush!