I think JrsBugs is closest with the Ptilimnium capillaceum suggestion. The plant is growing on a very hot, dry street corner with no irrigation (and we are in yet another drought period in Florida), so I don't think it could survive if it were a marsh plant.
Also, the leaves are more like dill or fennel, rather than being parsley-like.
I will check back with the plant, get some more photos and see if any seeds have developed.
Thanks for the input!
Jeremy
