What plant is that?

Our Mystery Plant for May is a lovely little native found mid-summer in moist soils across the northeastern coastal lowlands. It is tiny – between 4 and 8 inches tall – and its irregularly shaped pink-purple flowers are grouped into little barrel-shaped heads. Each flower is subtended by a pair of greenish-white and purple bracts that are about as wide as they are long. The linear and entire leaves occur in whorls of four. This is a species of concern in Rhode Island, but not hard to find if you know when and where to look. [If you want to key this plant using GoBotany you must use the Full Key]