Stipules can be hard things to figure out. Some of 'em go around the stem; some don't; some are almost invisible. I just recently heard that they're used for tree identification, but you have to be able to find 'em. I'd say you have to be pretty knowledgeable about trees to be able to stipulate the explicit stipule conformation on specific species. A mere hobbyist, I sure as heck can't. Yet.