Short answers, pulled from the story.
Wilhelm Mannhardt (the 26th of March 1831 - the 25th of December 1880) was a German mythologist and folklorist known for his research on Germanic mythology, Baltic mythology, and other pre-Christian European pantheons. He is particularly noted for his large-scale questionnaire survey of agrarian rituals and his work on vegetation spirits and the primitive tree cult.
Mannhardt's interest was sparked by reading two books: Jakob Grimm's Deutsche Mythologie and Jung-Stilling's autobiography. He was raised in Danzig by a Mennonite preacher, and this religious upbringing combined with those texts drew him toward the study of folk belief and ancient myth.
In 1865, Mannhardt sent out 150,000 questionnaires in several languages to clergymen, teachers, colleagues, and farmers' associations to collect information on agrarian traditions, rituals, and superstitions. The data gathered fed directly into his major two-volume work Wald- und Feldkulte, published in 1875 and 1877.
Early in his career, Mannhardt championed the solar theory under the influence of Jakob Grimm, reading myths as encodings of solar phenomena. Later, he shifted to an evolutionist view, arguing that vegetation spirits and the primitive tree cult represented the oldest layer of religion, from which more elaborate mythologies developed.
Mannhardt's manuscripts are held at the Berlin University Library.
Due to ill health, Mannhardt spent the last seventeen years of his life as a librarian at the Danzig municipal library. Despite this, he continued to write and publish scholarly and literary works until his death on the 25th of December 1880.