Thanks for responding nomen. The link you sent me is full of helpful information. I did some further searching and also found a great post: http://cactiguide.com/forum/viewtopic.php?t=10071. I am going to try the seasonal watering schedule suggested in the studies. I am still not clear about whether to drench the pot or just add a few drops of water. The study you sent me states: "It (P. Nelli) does not do well unless it receives some water all winter long, as the flowers are borne by the newly produced leaf-pair, which coexists with the old for several months". The study that I found doesn't say much. LOL. All this fuss over a plant that cost $ 3.48! Can someone please chime if they know how much water and how often? These two links are also great for others who are trying to figure out how to care for these split rocks: http://cactiguide.com/forum/viewtopic.php?t=10071

It liiiiives!! Cutting off the rot worked wonderfully. But I think the "surgery" worked in my favor because I spotted the rot almost immediately. Its doing just fine now, it's even sprouting new leaves! I took pictues of the rot and the "surgery" if anyone is interested. Eventually, new leaves will replace the old and it will look like nothing ever happened.

In my experience, sometimes a store-bought plant will fail on you and you'll never really know why. It could be that when you bring it home, it struggled to adjust to the new environment. I've also noticed that sometimes, up-potting and repotting will shock a new plant. Regarding watering in my experience, after it's done flowering and you aren't seeing that fresh new pair of leaves start pushing through, it's okay to water. This mesemb is supposed to have 2 sets of leaves, not only 1 pair like yours currently does. But don't panic, it'll be ok like that. It may or may not take several months for it to grow anything new. Like Kara said, it should be ok to pot up. You don't need to water it for a while. like 2 weeks maybe. I look for cues from the plant itself on when it wants water. I've noticed that with these plants, if the outermost leaves are a bit soft, NOT MUSHY- just if it loses a bit of that turgidity, it wants a nice drink. And a note about watering, especially in gritty mix. You should not live in fear of watering. If you water sparsely because you are nervous, the plant will lose the finer roots that help it take up water. And if you eventually give it a nice deep watering, it might die because there is suddenly too much water it can't absorb. But with that kind of gritty mix, I don't think you will run into this too-much-water-problem... Remember though, that if the months are turning colder, it will not need as much water.

Yep, looks overwatered. Mesembs are the most emo plants on the planet. Try not to get attached to them until they've acquired some tenure (about a couple of years, I'd say and even then they still could turn on you). Nothing to do, at this point. Just leave it alone. I suspect you only just got it and replanted it? Putting aside the amount of discussion that would go into what kind of soil they should be planted in, what I do with newly-acquired mesemb is to initially water it lightly---measured in tablespoons. Then run to google and find out if what you have is a summer grower or a cold-weather grower. P. nelii is basically an opportunist and will grow throughout the year if you are careful but it will drop into dormancy if it is very hot. Once they get to the point of detaching from the stem with the center turning into mush, that's pretty much it. And yes, it can happen very fast (plant cells explode from absorbing too much water).