Magnified apples appear and disappear, (line 18)
This line illustrates a problem in interpreting the poem: many of the images could be ascribed either to dreaming, to memories from earlier in the day, or to present events. The speaker seems to be having an after-vision of apples, having stared at them all day.
The woodchuck could say whether it's like his Long sleep, as I describe its coming on, (lines 40-41)
Although in a normal waking state he would know perfectly well that the only kind of sleep he can have, as a human, is "human sleep," in his drowsiness he hovers on the edge of another kind of reality. He almost thinks he could be like a woodchuck who hibernates through the whole winter. A "long sleep" could also be a symbol for death.