My house came with this cactus and it has survived several owners. It's part of the house. The previous owner potted it in rocks and told me she gave it a cup or two of water once a month or so. It grew many feet under her care so I aimed to continue her regiment. It has been 3.5 years and apparently I started well but I must've blundered somewhere along the way, because I see that many branches have dried out (and are dry & black inside). I'm not totally sure but I'm thinking now that probably the main trunk is dead. It still seems hard but that outermost layer peels away readily and I don't see any sign of moisture. Maybe at this point I should just cut off the branches that are still green and root them? Is it possibly to root large branches or should I only aim for small ones? Do I need to cut them right where they begin or can they be cut anywhere along their length? In other words, can branches that are half-dead be rooted? Can I just stick them in sand or do they need some other treatment? And last but not least, what exactly is this thing? Anyway, here are some pictures: http://picasaweb.google.com/thecherie/Cactus Thank you for the advice!