That stuff that's growing on the rocks, the gray-green stuff? That's lichen, and there are too many types of it to count. Also, lichen is important because later on in the future, that lichen will be the base of a plant, and all nature areas like this one were once only lichen, so I guess you should have lichen to thank for making this place as beautiful as it currently is. Moss is often the first to grow off of lichen such as this moss here. Posts 16 and 17 are past the rocks, so go check them out.