From the pictures I have been able to find on Google Images, U. gibba looks very similar in its growth form to U. olivacea. Which ever species we have had, it is something that many of us have had at some time or other, and have managed to get rid of. It forms an untidy mat at the surface or grows among other plants in a tangle and is about as welcome as duckweed. Another plant like it is Eleocharis vivipara. By the way, I found a strange website called Galleria Carnivora that has a very large collection of Utricularia pictures:http://www.sarracenia.com/galleria/g124.html