leaves in the wind. And the children, listening to the wind and inhaling "the pure fragrance of the water," would lose themselves in daydreams.

The two qualities that Paul initially associates with the poplar trees are the love that he and the other children had for them, and also the effect which they still have on him, which is to make his "heart pause in its beating." His heart pauses, or skips a beat, because the memory either excites him or scares him—or possibly both excites and scares him at the same time.

He does subsequently associate other qualities with the poplar trees too. For example, he says that memories like and including those of the poplar trees always have the quality of stillness, and also quietness, in sharp contrast of course to the noise and chaos of the war he is currently in. He then also says that these memories awaken in him a "sorrow—a vast, inapprehensible melancholy." This is because he is sad that he can no longer enjoy, as he once could, the poplar trees, and the stream, at least not outside of his memories.

After the horrors of battle, Paul and the other soldiers become

...insensible dead men who through some trick, some dreadful magic, are still able to run and kill.

As he stands on sentry, the benumbed Paul, like an experienced old man, finds himself besieged by memory, that sensation that controls people rather than the other way around. In his "vast, inapprehensible melancholy," Paul recalls the world that he has lost, a world of youthful ideals that is no longer attainable.  He narrates, "We could never regain the old intimacy with those scenes."

Paul recalls the grove of poplar trees under which he and his friends felt safe. The clean, fresh air, "the pure fragrance of the water" and " the melody of the wind" held the boys' fascination.  He and his friends dearly loved these two qualities of the poplar grove, so much so that as he stands sentry, Paul feels a pang in his heart for what he has lost in his young heart.