Stanza 3 Summary

Get out the microscope, because we’re going through this poem line-by-line.

My sparrow, you are not here,
Waiting like a fern, making a spiny shadow.

For the first time in the poem, the speaker addresses Jane directly, but not by name, calling her instead, "My sparrow."
The third stanza begins with a return to the bird metaphor. This time she is a sparrow, but she is gone and the speaker laments her absence.
The speaker acknowledges that she (the bird/Jane) is not there, "waiting like a fern."
Roethke builds on the bird metaphor with the addition of a simile, comparing the bird/Jane to a plant, a fern, casting a spiny shadow.
Spiny sounds a little prickly, but the delicate, complex pattern of the fern leaf would cast a beautiful shadow. See for yourself.
This description gives us, perhaps, more insight into Jane's complexity of character: she is, at times, dark and aloof, but she posses a complex beauty in form and personality.

The sides of wet stones cannot console me,
Nor the moss, wound with the last light.

There is nothing that will help ease the speaker's pain over the loss of Jane.
Roethke uses very descriptive, tactile lines to let us feel and see the depths of the speaker's sadness.
We can almost feel the smooth, cool, wet stones. We can imagine how, on a hot day, the wet stones would offer welcome relief from the hot sun. But they do nothing to console the speaker.
The description of the delicate moss, dappled with rays of light from the setting sun, is a moment of true, unusual, natural beauty; but it still cannot distract the speaker from his grief.