"On the contrary," Snape murmured without sparing a glance from that slow, patient slide of the grater along the claw, the steady snow of claw filings sifting down into the cup, "that's the whole point of putting those two together in the same jar. The water they're in is the 'Spring Pond' of the brew's name. And I'm sure you're aware that Spring's the time of year when the sap rises," he added with a cynical sneer. Scrape, scrape, scrape.