Figure 18, Leafy twig and fruit of Populus fremontii toumeyi x 3/5.

Drawn by A. E. Hoyle, in:

Sudworth, George B. Poplars Principal Tree Willows and Walnuts of the Rocky Mountian Region. (Washington, D.C.: U. S. Department of Agriculture, 1934) p. 35.

U.S. Forest Service Headquarters History Collection.