[Slughorn is snipping tentacular leaves through a window in the greenhouse; Harry, who is walking by, notices Slughorn and walks up behind him. Slughorn is startled]
Horace Slughorn: Aaauughh!... Merlin's beard, Harry!
Harry Potter: Oh, sorry, sir, I should've announced myself. Cleared my throat. Coughed. You probably feared I was Professor Sprout!
Horace Slughorn: Yes, I did actually!... What made you think that?
Harry Potter: Oh, well, just the general behavior, sir - the sneaking around, jumping when you saw me... Are those tentacular leaves, sir? They're very valuable, aren't they?
Horace Slughorn: Ten Galleons a leaf to the right buyer!... Not that I'm familiar with any such back alley transactions, but one does hear rumors. My own interests are purely academic, of course.
Harry Potter: Personally, these plants always kind of freak me out.