Jens Clausen

His parents were farmers and at age 14 he took responsibility for the family farm and was largely educated at home with the assistance of a local school teacher.

He completed his master's degree in 1920 and was appointed assistant professor to geneticist Øjvind Winge at the Royal Veterinary and Agricultural University in Copenhagen.

[2] In 1926, Clausen was awarded his Ph.D. for his work on Violaceae; his monograph was one of the first publications that combined systematics, ecology and genetics for any plant group.

During 1927-1928, Clausen received a Rockefeller scholarship to study at the University of California, Berkeley where he worked on the genetics of the genus Crepis with E. B. Babcock.

[3] Collectively Clausen, Keck and Hiesey wrote five books on their work, including Experimental Studies on the Nature of Species.

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.