Imagism was a poetic movement begun in the early 20th century. Its goal was to move away from long poems that told a story. Imagism, in contrast, often tried to capture the look and feel of a single image. An image is something you experience with one or more of your five senses: seeing, hearing, touching, smelling, or tasting. A typical imagist poem is short, more like a painting than a story and often, like a painting, very visual. You look at the poem as you would a painting and try to see in your mind's eye what the poet is describing. Imagist poems tend to use few verbs because they are not trying to depict an action but rather describe an object.
With that definition in mind, it is easy to see how both "In a Station by the Metro" and "Sea Rose" are excellent examples of imagist poems. Both are short and focused on a single image. Pound's very short, 14-word poem has no verbs. His poem also has no story but instead likens the ghostly image (what he calls an "apparition") of the faces of people in a crowded metro station to petals on a wet tree branch. Although he tells no story, he invites us, as readers, to stop and wonder if this what a crowd of faces in a subway station really looks like. If you have to write more about this, you might think about the following: What kind of image is a flower petal? Beautiful or ugly? Delicate or heavy? What does the image of flower petals convey about the people waiting to travel on a subway train? Can you imagine their faces as like flower petals? What do flower petals, especially wet ones, look like to you?
Likewise, H.D.'s (Doolittle often signed her poems H.D.) poem, while longer, is still short. It is about a flower too, in this case a rose. She does use verbs, but she is not telling a story. Instead, she is using the verbs to show the movement of the rose. Her imagery is harsh as she leads us to picture a rose blown across the sand by the wind. This rose is "meagre" and "stunted." She invites us to watch it as it is "caught in the drift," (a drift would be sand blown into a pile by the wind) then "flung" and "lifted" in the sand. H.D. tells us this rose is "precious." Why would this be? Perhaps because it is all by itself in this setting? The poem ends with a question that appeals to our senses, this time our senses of smell and of sight, asking if the rose can drip "an acrid fragrance" while so tightly "hardened in a leaf." This final image would suggest that the rose has not yet bloomed and is just a bud. What do you picture when you picture sand and wind and a single rosebud blowing across this landscape?
Both poems are imagist because they are short, compact, and focus on description, not narration.