"It depends who's put what into whose and to what purpose, doesn't it," he returns implacably.
"...That's... certainly... one interpretation," he allows rather faintly, very obviously restraining himself from slamming his head against the table or something.
"Nearly nothing, he was simply on the installment plan. No, I was thinking of Vector, Sprout, and Flitwick. Whatever you may think of the latter two as house heads or individuals, they're entirely competent in the classroom." Obviously he's not going to name any Gryffs here.
"I wouldn't know," he retorts, droll. "Thankfully, the invitation was never confirmed."
"You needn't--" he begins, but shuts up at the Look he gets. "Across the pond in the state of Kentucky is, I believe, your best option," he says, squinting into the air as though reading something off the inside of his skull. "Or Nova Scotia, if that fails. But the Pennyroyal Plateau is a known and more localized site; you should be able to find some on any of several hills. Will you be able to recognize the plant?"