Wikijunior:Summer Flowers of Northern New England/Silene latifolia
This flower has a feature behind the petals that looks like a balloon. Scientists call the balloon a calyx (kal-ix), but it looks more like a miniature watermelon. Note that the balloon is covered with hair (that can help you tell the difference between it and its near-twin, Bladder Campion. The flowers grow in clusters at the end of the stem. White Campion grows to be a couple of feet tall.