Well, the name says it all. For those who may not know, I got this from Wikipedia.
Dryads are female tree spirits in Greek mythology. In Greek drys signifies 'oak,' from an Indo-European root *derew(o)- 'tree' or 'wood.' Thus dryads are specifically the nymphs of oak trees, though the term has come to be used for all tree nymphs in general. They were also, in some respects, considered to be the elementals given the power over, also even said to be composed of the element of, wood. "Such deities are very much overshadowed by the divine figures defined through poetry and cult," Walter Burkert remarked of Greek nature deities (Burkert 1986, p174). Normally considered to be very shy creatures, except around the goddess Artemis who was known to be a friend to most nymphs. [1]
Hope this explains the "soul of there own" =)
Derek