Disclaimer: I don't own them, JK does, although I do appreciate the chance to play with them!
"Why can't you just admit I'm right?""Because, my dear, you aren't."
"Severus, it specifically states that the scales of the Hungarian Horntail and the Romanian Longhorn are interchangeable in this potion."
"I realize that. However, as I recall, the question was not what are the acceptable ingredients for this potion, but rather, what are the ingredients for the Draconigena Potion."
"That's right, what are the ingredients, not what is the universally accepted recipe for the Draconigena Potion, or even what is the generally used recipe!"
"Precisely, you provided neither. Romanian Longhorn is not 'ON' any recipe."
"You are unbelievable!"