The leaflets of partridge sensitive-pea (Chamaecrista fasciculata) is called 'sensitive' because the leaves fold together when touched with a finger. This species is native to southern New England, and introduced in New Hampshire.
Mimosa pudica, also called sensitive plant, sleepy plant and the touch-me-not is a source of fascination to adults and children alike. When touched, the narrow fern-like leaflets they almost instantaneously fold together and the leaf stalk droops. This sometimes sets off a chain reaction, with several leaf stalks falling on top of one another.