The Purple Pileus by H. G. Wells

The Purple Pileus is a short story by H. G. Wells. The story tells of its curious effect on Mr. Coombes, an unassuming, inoffensive little man in the grocery line, and upon his wife, his wife's friends, his business, and his whole manner of life. Another oddball Wells story. The entry in The Penguin Encyclopedia of Horror and the Supernatural led me to believe that this was a story involving a m