While out paddling along the river with the Sheep, Alice catches sight of some gloriously beautiful rushes (a type of aquatic plant). The Sheep allows Alice to stop and cut rushes, but in Alice's happiness, she doesn't notice that the rushes she cuts begin to wilt immediately—instead, Alice notices only that the rushes that are a bit too far away for her to reach are the most beautiful. With this, the rushes come to represent the process of growing up. Specifically, the quickly expiring rushes speak to how quickly childhood passes and how individuals cannot always recognize the ways in which they're rapidly growing and changing, while the beautiful but unreachable ones point to the ways in which children idealize both adulthood and the next level of maturity.
Rushes Quotes in Through the Looking-Glass
"The prettiest are always further!" she said at last, with a sigh at the obstinacy of the rushes in growing so far off as, with flushed cheeks and dripping hair and hands, she scrambled back into her place, and began to arrange her new-found treasures.
What mattered it to her just then that the rushes had begun to fade, and to lose all their scent and beauty, from the very moment that she picked them? Even real scented rushes, you know, last only a very little while—and these, being dream-rushes, melted away almost like snow, as they lay in heaps at her feet—but Alice hardly noticed this [...]