Almost everyone is familiar with the commonly kept potted plant called sensitive plant or touch-me-not, which closes its leaves when touched. It is a type of shrub that is not very cold-hardy and so doesn't grow wild in most of this country. We do have an equivalent plant called the sensitive brier (Schrankia uncinata), since its habit is to sprawl along the ground like other prickly vines and briers. Just like the sensitive plant, this brier has small pink puffy flowers and touch-responsive leaves. It also has small thorns, and so it has another line of defence against anything brushing against it.
The pink blossoms are actually a cluster of many flowers, each having tiny, hidden petals and prominent pink stamens with yellow tips. In keeping with the plant's prickly nature, even the seed pods are covered with tiny thorns.
To see the result of touching the leaves, move your computer's mouse over the picture below.