I have a stolon growing from my Besseae var Flavum and I have been told that it can be removed if you wrap sphag around the root base and let them grow into it a few inches in length. The sphag should be kept moist by keeping the whole ball encased in a plastic covering. A little tricky but if you manage to do it properly you can then remove the stolonous growth and plant it into the medium properly. I haven't done this myself yet as it is in bud and rather annoyingly it is starting a new growth from where I was going to wrap it in sphag. I shall wait until flowering is over then wrap the roots then.