Have grown species Clematis from seed, especially the herbaceous types. Very easy as long as the seed is fresh. the seed has a very short life span so dried seed is often dead.

I've never bothered with seed since layering works very well for me.

Like Owdboggy I ahve grown species clematis from seed. I have aquired my seed from a seed exchange where current years seed is submitted in October and the seed distributed the following January to be sown straight away. This has worked well enought for me.

This looks very like one Hywel wanted identifying a few weeks ago. Have a look through his recent blogs and questions.

Thank you all for your replies. Seems fresh seed is needed so perhaps relying on buying some on the internet is possibly not a good idea, so thanks for that bit of info Owd.
Hazeyboo - layering is fine if you have the plant to start with, if not it's a matter of finding it or growing from seed.
Seed exchanges are a great idea Bulbaholic and I used to belong to the Primula one, but a few seeds off the internet will possibly be old.
I will have a look at Hywel's questions for that Stera, thanks.