Looks like diatoms- brown algae. How long have you had your tank up and running? If it is, all you have to do is maintenance- use your fingers to rub it off, a soft tooth brush, or something to wipe it off. So long as you keep it at bay, it'll eventually go away- sometimes it still comes back, but its algae- you're going to get at least a little bit of it in your fish tank regardless...
Edit: Also, what kind of plant is that? Is it real or fake? Looks real, but kinda hard to tell in the pic ^.^;;