I have saved the whole dry seedheads, but I am not sure what part is the seed (unless they are sterile). I gathered these while walking to the post office, so I am not sure of the exact cultivar.

I answered my own question by looking at the sticky, so I'll share the link while I have it all typed in. Maybe others are interested.

http://theseedsite.co.uk/db3.h...

Now, time to look up seeds on Begonias.....