Varenka is excited by the charged atmosphere of possible proposal, and Koznyshev realizes he has intense feelings for her. He goes off to gather mushrooms on his own and deliberate. He determines that Varenka is everything he wants in a wife. Seeing her in the distance, he throws his cigar away and advances purposefully toward her.
Everything is set up perfectly for Koznyshev to propose to Varenka: they are alone together gathering mushrooms, which gives Koznyshev time to gather his thoughts and muster his courage.