As the dryad rides you toward a climax you feel yourself becoming even harder. You've heard people talk about being "rock hard" but this no longer feels like a euphemism. You begin to feel stiff all over - you can't move!
"What's happening to me?" you ask.
"I love trees" replies the dryad.
You feel your arms spread wide. Your body no longer feels the same, nor does the dryad's touch feel like a person touching your skin, although you can still feel it. A light breeze tickles your skin. Finally you erupt into the dryad who squeals with delight. Your orgasm brings a finally stiffening. You don't feel flaccid at all even though you're finished.
The dryad finally stops riding you, but doesn't slide off of you yet. Your wood is still between her legs.
And with that thought you realized what has happened.
"Thank you for joining my forest."