How can I analyze the poem "In a Station of the Metro" by Ezra Pound? What are the theme, shift(s) and attitude of the poem?

At first blush, "In a Station of the Metro" seems impossibly easy.  After all, it is a two-line poem.  That being said, there is a lot going on within the few words we get from Ezra Pound.

The title and first line place us at "the Metro" -- Paris' cleaner version of the NYC subway system.  His first line, "The apparition of these faces in the crowd" firmly places the speaker in the Metro.  The...

At first blush, "In a Station of the Metro" seems impossibly easy.  After all, it is a two-line poem.  That being said, there is a lot going on within the few words we get from Ezra Pound.

The title and first line place us at "the Metro" -- Paris' cleaner version of the NYC subway system.  His first line, "The apparition of these faces in the crowd" firmly places the speaker in the Metro.  The use of "apparition" indicates that the faces are moving quickly in and out of his view, almost like ghosts.  The fact that he only refers to people by their "faces" likewise seems to dehumanize and disembody them.

In the second line, however, we shift from the decidedly unattractive Metro scene.  Here, he makes the metaphor that these apparitions whose faces he sees are, in fact, "Petals on a wet, black bough."  He is comparing the disembodied faces to petals on a branch.  This seems to suggest a connectedness between the people, one that we did not see when they were only apparitions and faces.  The fact that he uses the metaphor of a tree branch is likely not an accident.  Ezra Pound was a big fan of Japanese literature and a student of haiku.  The poem itself is a modified haiku, and the tree branch is likely a nod to the flowering trees prevalent in Japan.

In the end, then, there are two main possibilities for theme here.  One is that even seemingly disconnected entities are connected in the bigger picture.  The other is that beauty may be found everywhere, even in the seemingly ugly surroundings of the Metro.  The shift in tone and attitude from the busyness and disconnectedness of the first line to the beauty of the second serves to drive this point home.