I have all of these species in my collection. I think ´Mammillaria micromeris´ has now been placed in
Epithelantha micromeris by the International Cactaceae Systematics Group - who pontificate on these things.
Pelecyphora asseliformis is certainly a slower grower than
Lophophora williamsii, as are many of the other species I have.
Aztekium ritteri is possibly the slowest growing cactus (plant, even?) of all - and is one of the very few I have on a graft in my collection.
Hostilis, I love the cristate form of
Aztekium ritteri that you posted !!! Is it yours? is it for sale - or trade?? Hey I see it is on ´cactus-art´ so I guess not ( and I see now that all of your pics have been taken from there - nothing of your own then) !!!!
Aztekium hintonii is a lot faster growing - mine came into flower last week - pic attached (taken by me of my own plant).
Spanishfly attached the following image(s):
Aztekium hintonii.JPG
(214kb) downloaded 62 time(s).Life is a shit sandwich - the more bread you got, the less shit you eat.