The two poplars of this experiment are on the parking of a street running north and south. At three feet above ground, where the temperatures were taken, the south tree is 18.5 inches and the north tree 16 inches in diameter. All lower branches have been removed to a height of 16 feet or more and there are no obstructions to forenoon or afternoon sunlight. They are openly situated.
Proceedings of the Iowa Academy of Science
©1932 Iowa Academy of Science, Inc.
Martin, J. N.
"The Daily and Seasonable Variation in the Internal Temperatures of Two Trees, Populus deltoides Marsh,"
Proceedings of the Iowa Academy of Science, 39(1), 63-63.
Available at: https://scholarworks.uni.edu/pias/vol39/iss1/11