Please provide a summary of the "Apple Tree" section of this book.

The unnamed male protagonist has lost his wife, Midge, to pneumonia. He has mixed feelings about his loss, for the gloomy Midge had made him feel guilty by acting the martyr. Grief quickly gives way to relief and even enjoyment, and then he notices that an apple tree in the yard looks like Midge. The man’s current vision and memories of their earlier life combine to reveal a callous, self-centered husband, oblivious to how being childless and listening to his criticism had affected her. Every aspect of the tree becomes burdensome, assaulting all his senses; even the smell of the wood nauseates him, and he resents other people’s admiration of its flowers. Not only that particular tree but also its shorter neighbor call up his memories and sensations. The reader understands that his guilt was based in his indiscretion. When he finally decides the tree must go, he botches the project of chopping it down, and the tree instead destroys him.
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"The Apple Tree" is a story about a man who believes he is being haunted by the spirit of his dead wife, who the man thinks is inside an apple tree. The widower comes to accept his newfound freedom, yet feels like he is being oppressed by his deceased wife. Because of the wife's anger towards her husband for being happy about her demise, this apple tree, in particular, is menacingly positioned outside the bedroom window. The tree is described as having ugly blossoms and disgusting fruit, perhaps exhibiting the wife's vengeance. In a fit of blind rage, the man decides to chop down the tree yet is caught in the stump and unable to receive outside help.
Like most of Du Maurier's other stories within the collection, this story uses elements of goth and fantasy in order to provide a psychological analysis of the situation. Having an apple tree supposedly be inhabited by a vengeful wife to spite her husband can be interpreted as the manifestation of the man's paranoia about his wife possibly knowing about his infidelity in the past.