returning to the New York Botanical Garden where he would spend the rest of his career, he worked as a botanist in Brussels with the U.S. Foreign Aid Program from 1951 to 1952. He died of heart failure on March 22, 1992, while studying specimens of Mentzelia at the herbarium at Brigham Young University. Work Development of the Cronquist system While Cronquist was in his mid-thirties, he began to question the usefulness of Adolf Engler & Karl Prantl's taxonomic system, laid down in their work Die Natürlichen Pflanzenfamilien (The Natural Plant Families), which had been the dominant system since the late 19th century. Although Cronquist was originally involved mostly with the family Asteraceae rather than with general systems, he began publishing on the topic in 1957 after much discussion with his peers concerning the challenge of forming a new taxonomic system. His initial publication (Cronquist, 1957) dealt purely with dicotyledons. At the time he began his work on his general scheme of classification, several others were working with the same goal in mind, including the American Robert F. Thorne, the Dane Rolf Dahlgren, and Armen Takhtajan of the U.S.S.R. Each of them would go on to produce their own taxonomic schemes, though Cronquist's would prove to be the most widely adopted. While working on the project in the 1960s, Cronquist came to be close friends with Armen Takhtajan and both men put all of their information at one another's disposal. To this end Cronquist decided to learn Russian in order to have access to the scientific literature that the Soviet Union had accumulated, which was largely unknown to the rest of the world. He made several trips to the U.S.S.R. to meet with Takhtajan and other Soviet botanists and translated many botanical works from Russian throughout his life. Cronquist's first overview of classification was published in 1960, followed by his The Evolution and Classification of Flowering Plants in 1968 with a revised and expanded second edition being released in 1988. This work also was a survey of the practices of systematic botany. In 1981 he published his landmark work, An Integrated System of Classification of Flowering Plants. The work divided flowering plants into 2 classes with a number of subclasses and down to the family level, with each taxon being described and defined. The system would go on to be adopted by several major projects in floristics, including the Jepson