The Narrow-leaved Cottonwood (P. angustifolia, James) has lanceolate leaves, more like a willow's than a poplar's. The margins are finely saw toothed, the petioles short, and the texture thin and firm. It is easy to see that the tree is a poplar, the flattened petiole alone being a sufficient clue. The tree lines the hanks of mountain streams of the Rockies, 5,000 to 10,000 feet in elevation. It grows from 40 to 60 feet high, a narrow pyramid of slender limbs.