petals on a wet, black bough

Ignoring the presence of metro platforms and rails, I realize that I've never fully thought about Ezra Pound's imagist petals before.*  [That's not true: I was teaching a Bread Loaf course on British poetry a few years back, and the student leading that particular class had us all draw what we thought that we saw when we read that poem: a terrific exercise.  Mine transposed quasi-Japanese stylized cherry blossom onto a subway station with curving tracks].  I'll try again: I've never properly thought about the preposition "on" - or rather, I've somehow assumed pink against black; petals against wood; flower against branch.  But today, looking out at our just-blossoming Asian pear, it struck me that maybe the branches, as here, support the petals.  And in fact, I've never thought of the blooms as well as the bark being wet, but of course, as here, they can be thought of as dripping.

As you'll see, Griffith Park, behind us, appears, to be in a wet, grey cloud.

* 

In a Station of the Metro

The apparition of these faces in the crowd;

Petals on a wet, black bough.

Ezra Pound, 1913