They planted peach, apple, and plum trees and acres of raspberries and blackberries, all of which took some years to mature. McCollum failed the general certification examination, but was allowed to enter high school provisionally based on his habit of extensive reading and his memorization of standard poetry. Though extremely shy around girls, he was elected class president in his junior and senior years. He fell in love with the school's Encyclopædia Britannica, purchased a set for $25 (about two months of his earnings), and used it for twenty-five years until he bought a new edition. In high school he joined the Unitarian church. He worked his way through high school and college, including time spent as a gas lamplighter. While a junior in college, McCollum was elected to Sigma Xi, a non-profit honor society for those interested in science and engineering. As his mother had hoped, McCollum graduated from the University of Kansas in 1903. While there, he abandoned the dream of becoming a doctor, and during his sophomore year, he consumed organic chemistry, earning a bachelor's degree in three years, followed by his master's in 1904. He secured a scholarship to Yale University in 1904, and wrote his thesis on pyrimidines. McCollum got his Ph.D. from Yale in two years. He remained for another year as a postdoctoral researcher working with Thomas Osborne and Lafayette Mendel on plant protein and diet. Then Mendel found a position for McCollum at the University of Wisconsin–Madison, not in his preferred organic chemistry, but as an instructor in agricultural chemistry, where Dennis Robert Hoagland enrolled as a master's student in 1912/1913. In 1907 he married Constance Carruth, whom he had known in Lawrence. They had five children (Donald, Jean, Margaret, Kathleen, and Elsbeth). The two divorced later in life. When he was living in Baltimore, in 1945, he married J.Ernestine Becker, a dietitian and co-author of one of his books. Single-grain experiment In Wisconsin, McCollum was assigned to analyze cow feed and the animal's milk, blood, feces, and urine for the famous single-grain experiment, directed by department chief Stephen Babcock and his successor Edwin B. Hart. The experiment ran for four years until 1911. Babcock had studied for his Ph.D. at the University of Göttingen in Germany prior to working at the New York State Agricultural Experiment Station and then joining the staff in Wisconsin. During this era, German chemists were trying