Sentence:  Instead there were the white of aspens, streaks of branch and slender trunk glistening from the green of leaves, and the darker green of <WSD>oaks</WSD>, and through the middle of this forest, from wall to wall, ran a winding line of brilliant green which marked the course of cottonwoods and willows. 
Meaning of the word marked with <WSD> tags:  (tree)  A deciduous tree with distinctive deeply lobed leaves, acorns, and notably strong wood, typically of England and northeastern North America, included in genus "Quercus".