I apologize to the moderators if there's a place more appropriate for this post: let me know and I will delete it ASAP.
This is that time of the year when you pick up all the seed you collected during the growing season and start planning next year's campaign. I have, as I'm sure most of you, a lot of seed I'm not planning to sow, as well as a few species I would REALLY like to try. That said, if anyone has seed of
Mammillaria deherdtiana (and its subspecies)
Mammillaria saboae (and its subspecies)
(preferably of known origin)
and is willing to part with it, I would gladly swap for other, possibly not-so-glamorous Mammillaria species, Turbinicarpus or Mediolobivia.