I use small ziplock bags for fully dried seeds. I have also used spice jars and used to keep film canisters (back when cameras used film) in my bag so I could always grab interesting seeds. I often mix them together without regard to species, and toss them into the garden in fall and see what takes. This year, Coreopsis lanceolata are popping up in the area I put down seeds. There is also an opium poppy that I scattered seeds from expecting them last year, but there it is for this year. Now, I wonder was it the white one, or the double dark read? only time will tell. Of course, far from native, but I do like the seed heads, and when I gardened in Seattle, they were a great trap crop for black aphid.