A Wagner Matinee

"[Howard] had characteristically delayed writing until, had I been away from home for a day, I must have missed my aunt altogether." 

The above passage is the first hint Cather provides that Georgiana's marriage may not be an entirely happy one. Clark's remark that his uncle's delay was "characteristic" suggests that Howard is—at best—prone to forgetfulness or procrastination. At worst, it implies that he was deliberately trying to inconvenience his wife. If we take Clark's words at face value, either option tends to depict the couple as ill-matched, since we will soon learn that Georgiana is both highly conscientious and sensitive.

"The name of my Aunt Georgiana opened before me a gulf of recollection so wide and deep that, as the letter dropped from my hand, I felt suddenly a stranger to all the present conditions of my existence, wholly ill at ease and out of place amid the familiar surroundings of my study." 

Clark's memories are a focal point in Cather's story, where they commonly deepen our understanding of character and setting; his descriptions of earlier interactions with his aunt, for instance, provide a reference point for how much she has changed over the years. They are also important in and of themselves, however, because the characters in the story display such a clear longing for the past. Although Clark's time in Nebraska was unhappy in many ways, his relationship with Georgiana was clearly one of the high points of his life. The reminder of her is therefore so powerful that it actually makes him "ill at ease" with his current circumstances (though they seem, on the whole, to be happy).