This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
P. deltoides occidentalis Rydb. Mem. N.
Autun 18: [reprint 40]. 1905. Populus occidentalis Britton; Tillotson,
Rep. Board. Agric. Nebr. 1906-7: 218.
Similar to P. deltoides, the bark thick and gray, the twigs smooth, greenish to light yellow. Leaves glabrous on both sides when mature, broadly triangular-ovate, often wider than long, subcordate to truncate at the base, rather long-acuminate at the apex, the margins coarsely and bluntly toothed; petioles flattened, about as long as the blades; stami-nate aments 2-3 1/2' long, not very dense; ripe pistillate aments 5' long or more; capsules ovoid, 5"""/ long, longer than their pedicels.