I don't know what kind, but I can say for certain it should not be growing in dirt. I'd guess the bark has broken down over the years and noone has repotted it. Dendrobiums are very hardy and even bark that is disintigrating generally doesn't slow them down much. lol Nice plant...if you repot carefully you won't lose buds and blooms. Good luck with your new dendrobium....it's a nice one!