Finding spirited presences in trees has long been part of woodland myth and folkore world wide. Here are other "tree people" images by some of my favorite mythic artists: Illustrations by Arthur Rackham From "The Land of Froud" by Brian.
Boggart An English folklore creature known for its relentless mischief. Can be quite malicious. Pranks include turning milk sour, waking sleeping babies, frightening pets etc. They cannot be reasoned with and are difficult to be rid of.
The Kelpie of Irish and Scottish lore. The kelpie will come to land as a beautiful horse, luring humans to it. Once a person gets on it's back, the kelpie races to the water, transforming to it's true water demon form, and drowns its victim.