Derrick woke slowly, sunlight warm on his body, but feeling curiously stiff. It took a few minutes before he was alert enough to realize he was standing in the middle of the clearing. He'd fallen sleep standing up? That was weird. There was laughter form the trees, and one of the green-skinned nymphs came dancing out.
He was still foggy, but remembered the almost excruciating pleasure of sex and groaned with a mix of apprehension and desire. The girl wrapped her arms around him and started to slide up and down, twisting and working around him. Oddly, the pressure of her embrace did not even make him stagger a step. She giggled and slid her hands up his sides and then pressed on his arms, urging him to raise them over his head. He complied, and though the position was awkward at first, it quickly felt natural.
As the nymph continued her erotic dance around him, he dimly realized that she was getting shorter. That was very strange. Her head was just over his waist, and then below it. He felt her hand caress his penis, which was swollen and hard again. It got harder, thicker, longer under her fingers, the pleasure sinking deep into his body. He was looking forward, and could not seem to look down. The sensations were intense though, his cock growing with each stroke, feeling like it was heavier and longer than an arm. Then something strange moved up into his field of vision. A branch was growing in front of his face. Even stranger, as smaller branches rapidly sprouted leaves, he could feel it all. Each leaf that emerged was like a mini ejaculation.
Other sensations were starting to get more intense - like a dozen more penises pushing out of his body, growing long and straight and thick with... leaves? Blinking, Derrick tried to force himself fully awake. He could no longer turn his had, but he could move his eyes enough to see the sturdy branches rising up on either side. And he was looking across at tree branches of other trees as he continued to grow. Other trees? Growing?
The truth hit Derrick hard, yet the horror was only momentary. He was becoming a tree. A great Oak. He could feel his new identity in the strong roots that reached down into the rich soil, in the lush foliage that was even now sprouting from a hundred branches. Each breeze rustling through his new leaves sent a wave of pleasure through him. And still he grew. He was huge now, fifty feet tall and still growing. Curious memories, more impressions, began to fill his mind. Seasons, many many seasons of losing leaves, gaining them, creatures living among his branches, storms, cold, heat. He was a hundred years old and still growing!