Mammillaria orcuttii?

This plant was brought to the UK Mamm Society AGM and was labeled M.orcuttii. It looks nothing like the plant I except has M.orcuttii, which is the PM 30 collection from Valle de los Fantasmas, SLP. I would be grateful if someone could give a more positive I.D. I told the owner that I would post it on the forum to see what others thought.

While it certainly doesn't look like my PM30 either, Mark, I wouldn't rule it out. Can you take a crop from your full size image of the spines and then post it at full size? The image here is too reduced to let me blow it up for a good look. It seems to have 4 short black spines, centrals?, but I can't see any radials? It looks like it might be starting to divide dichotomously as well? Do you know its provenance?
It is not dissimilar to the plant shown in Pilbeam on P210 of orcuttii in habitat, allowing for the fact that in cultivation it has grown taller. There's less wool in the apex, but that could just be light conditions. Do the flowrs have the pink midstripe that is typical? they look uniformly coloured, but that could again be variation.

Mark, thanks for the photo, I've tried to crop out an area and blow it up as below.



You can see clearly that the plant has radial spines, white, quite short, and approximately 16-18 in number. They seem to persist right down to the lower part of the body. That is not in accord with the only description I have of orcuttii, which is in Pilbeam, and states 6-8 very short, soon deciduous, white, hairlike, 2mm long radials. So either the description is wrong and the species is more variable than previously thought, or this is a different species.
I have found two other field references - ROG106b, but nothing else searching the web. Does anyone have a picture of the collection of this plant? The other is ML321 on Mammillarias.net, but this has white spines, not black, and the other picture of a plant in habitat is too small to tell, apart from also having paler spines. But if these also are orcuttii, then the description in Pilbeam certainly should be broadened.
If I were asked to make a judgement, I'd say that this was orcuttii, and that the description needs to be broadened, but without locality details for this plant there isn't enough data to do so.

In our photo galery are 2 exellent pictures of M. orcutti and in the reference plant collection album again 2 pictures of orcuttii SB1488 with spine details:
http://hugo3.myjalbum.net/Pflanzensammlung%20-%20%20%20Plant%20Collection/slides/DSC_0003%20M%20orcuttii%20SB%201488%20Santa%20Catarina%20San%20Luis%20Potosi%20Foto%20R%20Dehn.html

There is some question over what SB1488 is. I brought some plants by post listed has M.orcuttii SB 1488 and they turned out to be M.karwiniskiana ssp beiselii. The Raph Martin data base gives SB 1488 has M.aff karwinskiana while in Pilbeam, in the SB list, it is down has polythele - aff kewensis. I spoke to a member who had been in touch with Brack and he said Brack never colected M.orcuttii.
Reppenhagen collected REP1450 from west of Buennavista, SLP, which he called M.orcuttii and I think there was a picture posted on the forum. There are 2 cracking photo's in the Gallery by E.Spenkoeh taken at the T.L.

Thanks for the links and direction.
It is interesting, as the plants from habitat show no obvious signs of persistent radial spines, and centrals between 2 and 4, nice and black. The collection plants of SB1488 are way off being of the karwinskiana group, and both show persistent radial spines, and more than the Pilbeam description. Your plant was clearly mislabelled, Mark, or you were sent the wrong plant by mistake.
It could be that the radial spines persist in cultivation whereas in the wild they don't. If so then orcuttii is more variable than stated.

I had have a quick look at my 2 orcutti plants: Rog 106b shows no radial spines, the other one PM 30 shows up to 10 radials. The original description by Bodeker says that the radial spines dissapear with age

Hguo, could you post a picture of both of the plants together for me.

On demand:



The two plants show no segnificant differences except the small one PM 30 has radials.

Thanks hugo, that's what I expected to see, both from the same locality. I have E-Mailed Steve Brack to find out what he belives SB 1488 is. I'll post any reply he sends.

My M. orcuttii PM30, bought from Rod Preston-Mafham in May 1990, which is very much like the one shown here, a bit more cylindrical, and with about 8 whispy short radial spines which seem to drop off after a year or so.