At the end of the day, knowing that they would be graduating from college soon, they vowed that they would meet, in twenty years, at the same place and renew the experience.
Twenty years later, they met and traveled to a spot near where they had been years before. They walked into the woods and before long came upon a brook. One of the men said to the other, "This is the place!".
The other replied, "No, it's not!".
The first man said, "Yes, I do recognize the clover growing on the bank on the other side.
To which the other man replied, "Silly, you can't tell a brook by it's clover."