Hi Sue, You are very correct. When I enlarge the original to the point where the pixels are almost fuzzy, the leaves are precisely opposite- not alternate. The appearance might be due to over 50% of the leaves having fallen already: However, here is a copy where I have highlighted the leaf arrangement.
So for now the mystery goes "un-solved", but I still like whatever it is.
Thanks very much for your input.
Mystery Unsolved!