Nice trees

So, I told my boss today that I like being with the trees.

He asked me, "Why?"

I might have responded, "They make me feel good."

Then, there came this other question... "How?"

I thought for a few seconds and might have answered with something like... "I don't know... maybe some chemicals they released into the air?"

After I got home, I revisited the question of "how"... and thought... in addition to Oxygen, stuffs like phytoncide, perhaps?