In a Station of the Metro
Line 2: The success of the comparison between the human faces and the flower petals depends upon making the second image seem very life-like. So Pound uses some intense natural imagery to describe the "wet, black bough" to which the petals are attached. This image connects to our sense of sight and touch, so the reader feels like he or she could reach out and pluck the faces out of the scene like a flower from a tree. He also uses some alliteration with "black" and "bough," as if the words on the page and the images in our head were fusing together at the same time.