A stand of old-growth Douglas fir at the end of dusk, when the sky has not quite lost its last light — the canopy is near-black, a ceiling of dark layered needles, the trunks thick and deep pine-green where they catch the remaining light, and from the forest floor upward the air holds a dark sage-green that is the accumulated colour of ten thousand living things breathing in the dark, the whole forest a single organism composing itself for night.