Wim,
I had some seed of Anemone polianthes from SRGC seed exchange last January. I sowed the seed in a container and put it in a plastic bag to preserve moisture at +20C, then put it in the frige (I guess +8C) for 2 or 3 weeks, then retrieved from the frige and left at +20C again untill they germinated after which I removed the bag. There must be other ways. But this one appeared successful for me. The only problem was that some shoots came with a seed capsule intact, so I had to carefully remove them with a needle. Hope it will help
Oleg