pearance. Never let it be said that K. P. hid his light under a bushel.
Link returned to an assistant professorship in agricultural chemistry at the University of Wisconsin in 1927. In 1928 he was promoted to associate professor—shades of our present day hesitation in giving even the best of candidates tenure before five to seven years. But no mistake was made; the staff knew K. P. Link was capable as a teacher and researcher, and he justified their confidence many times over.
Link's thesis work under Tottingham was on the effect of temperature on the composition of corn seedlings and the nature of the principal carbohydrates in relation to seedling blight, and he retained his interest in plant biochemistry. After he had set up his lab, Link initiated studies on carbohydrate chemistry, and this is the area in which he first established his solid reputation. His microchemical lab was an important adjunct to his characterization of carbohydrate derivatives that he and his students isolated and synthesized. Although Link's interest was directed primarily to plant carbohydrates, he did collaborative work with J. C. Walker, a plant pathologist who became a member of the National Academy of Sciences in 1945. Link, Angell, and Walker (1929) found that brown onions contained protocatechuic acid and that it conferred resistance to the fungus Colletotrichium circinans, the causative agents of onion smudge. In contrast, the white onions lacked protocatechuic acid and were susceptible. As Link, Dickson, and Walker stated, "It appears that we have established for the first time a specific chemical difference between a resistant host (the pigmented onion) and a non-resistant host (the white onion)." This became a textbook example of a specific compound that could confer disease resistance on a plant.