Arnolds family moved to Ludlowville, New York and he attended Cornell University with the intent to study agriculture.[1] Interaction with Loren Petry, a Cornell professor studying Devonian plants of the region, lead to Arnold shifting his focus to paleobotany.[1] He received his Bachelor of Science in 1924, his Ph.D. in 1929 with his thesis on Devonian megafloral paleobotany.[1] He started working at the Faculty of Botany, University of Michigan from 1928 and became curator of the collection of fossil plants in 1929.