Aha! I'm sort of glad you didn't show the plant, because I would have said it sure looks like A. parallelifolia (one that I did grow - it's a choice small, clustering species, and Malagasy to boot!).
I still have the 180mm but after using the 100mm L macro I may sell it. The 100 is about a 1/3 the weight of the 180 and is so much easier to do handheld shots with. The 180 is still the best if you have a tripod handy.
