Nelsonia canescens, i think.
Exactly right. As I'm told, all Nelsonia species are being folded into N. canescens, which is simply widespread and variable. I was hoping that it would creep, as some plants from Australia apparently do, but it doesn't (this one is from Sao Tome and Principe off the west coast of Africa). FYI, Nelsonia is also the name of a genus of large rodents.That all depends on humidity levels i think. I'm currently growing Nelsonia emersed and it looks exactly like the plant in your picture.
It used to be called Nelsonia smithii, but i remember Cavan saying that the correct name was Nelsonia canescens.
Hopefully someone else can chime in with another opinion.