Engler, Adolf (äˈdôlf ĕngˈlər) [key], 1844–1930, German botanist. He emphasized the importance of geological history in the study of plant geography, and worked out an influential system of plant classification. A professor at the Univ. of Berlin and director of the botanical gardens (1889–1921) there, he founded and edited (from 1881) the periodical Botanische Jahrbücher. He wrote several works on plant geography and taxonomy, and collaborated with Karl Prantl on the early volumes of Die natürlichen Pflanzenfamilien (32 vol. in 17, 1887–1909) and edited the early volumes of Das Pflanzenreich. The Engler and Prantl system of flowering plant classification was the principal one in use until the 1970s.