Posted: Wed Oct 20, 2010 9:55 pm
Done and done!
Hi Peter,
Don't know if you're still looking in here, but for anyone who is, your "O. phaeacantha" photos here are probably O. phaeacantha phaeacantha. Based on the type specimen (from not too far away at roughly Pena Blanca), I'm not sure there really need to be any varieties of O. phaeacantha, but some populations in California (aka peircei) and some in Mexico are perhaps different enough to distinguish. Most of the so-called "varieties" of O. phaeacantha are really distinct species and very different.
The photo you thought might be "pottsii" here is O. camanchica, which was described also from not far away near Newkirk, NM. It is similar to O. phaeacantha, but tends to be stockier with often broader and thicker pads, and with more woody tissue inside. O. pottsii itself is a small soft plant that flops in the winter (much smaller than O. camanchica), with more slender spines and growing from a central swollen tuberous taproot. It's often mistaken for a seedling of something else. O. camanchica has been treated as a variety of O. phaeacantha, but since they often grow together and remain distinct, I prefer to treat them as different species. A coupld of other names given to the same type of plant as O. camanchica are "O. phaeacantha brunnea" and "O. chihuahuensis".