I am going to let twit address that question Charleen. I can tell the difference but afraid I would really only confuse you with trying to tell you the difference. : )
Until twit posts here is a short version. Semps produce offsets from long to short stolons. Heuffs produce offsets from the rosettes own root instead of a stolen.
Here is an expample of J. heuffelii 'Bronze Ingot', see how the rosettes appear to be all squished together? That is because they are growing from the same root.
