Well, only "in case of disagreement between [the House and Senate]". And since those bodies usually convene and adjourn independently, then one should be able to argue that they have agreed on such independence, rendering the President powerless. Also, the "adjourn to" language makes me suspect that he would have to state a time of their reconvening. Plus, every two years there's a new Congress, so things should return to default status then.

But I'm just trying to interpret vague language that, as I said before, has probably never been used. After all, it's a myth that our (the U.S.) Constitution was all written down in 1787, as our "strict constructionists" pretend. Really, we rely on tradition just as much as the UK's unwritten constitution, and even Supreme Court decisions have recognised this. So if any President tried to activate these powers, then this would cause a constitutional crisis, just as if (in the UK) the Sovereign were to try to exercise theoretical powers that have not been used for centuries. ("Sorry, Mr Blair, I don't accept your resignation, and I refuse to appoint Mr Brown, because I don't like his looks.")