on their work, including Experimental Studies on the Nature of Species. I. Effect of Varied Environments on Western North American Plants published in 1940 and Experimental Studies on the Nature of Species. III. Environmental Responses of Climatic Races of Achillea in 1948. Clausen produced one additional book about his work based on the Messenger Lectures he gave at Cornell which was published in 1951 as Stages in the Evolution of Plant Species. Honors Clausen was elected a member of the National Academy of Sciences, the American Academy of Arts and Sciences, and the Royal Swedish Academy of Sciences; he was also a member of the Botanical Society of America, and the Society for the Study of Evolution. He was a fellow of the California Academy of Sciences and of the American Association for the Advancement of Science. He was knighted in the Order of the Danneborg by Frederick IX of Denmark. Clausen was a member of the First Baptist Church of Palo Alto, California. Family Clausen was married to Anna Hansen. Anna supported and assisted with Clausen's scientific career by undertaking "artificial pollinations, back-crossings, fixations, baggings and harvesting" of plants, as well as assisting with the recording and numbering of segregated types, thus providing material and data upon which some of his scientific writings were based. References Other sources Smocovitis, V. B. (2000) Clausen, Jens Christen in "American National Biography Online" (Oxford University Press) External links National Academy of Sciences Biographical Memoir 1891 births 1969 deaths Evolutionary biologists University of California, Berkeley alumni University of Copenhagen alumni Members of the Royal Swedish Academy of Sciences Danish emigrants to the United States 20th-century Danish botanists Danish geneticists American geneticists Order of the Dannebrog Members of the United States National Academy of Sciences People from Guldborgsund Municipality