Mammillaria sp. SB1566

I was wondering about this plant, which comes from N of Ascencion, NL.
It looks like a form of M. heyderi to me, and probbaly close to the ssp. hemisphaerica. However, I believe it has napiform roots, whereas the normal situation for heyderi is to have fibrous roots.

Does anyone think that the type of roots are significant? or any other suggestions for this species?

This ia my plant of SB 1566. I have four of these plants grown from seed from Mesa Gardens via the UK Mammillaria Society 2001 seed list.
All the plants look the same apart from one, which has short and blacker spines. For me thay are M.heyderi and not sub hemisphaerica.

url=https://servimg.com/view/13261353/263]

Here is the same plant knocked out of it's pot to show the roots.



M.heyderi heyderi covers such a large area that I am sure that there are going to be some plants somewhere with a sightly different root system.

My SB1566 from The Mammillaria Society Seed Distribution 2000

these are my SB 1566 in flower on may 14, 2011