By 1895 it was well known that Lambert's Pinus taxifolia was a later homonym. However, if one considered Poiret's Abies taxifolia to be a new name for Pinus taxifolia, as Sudworth suggested, then the epithet "taxifolia" becomes available for use in Pseudotsuga. Sudworth then proposed Pseudotsuga taxifolia (Poir.) Britt. ex Sudw. in 1897. Unfortunately, at this time it was not known that even Poiret's Abies taxifolia was a later homonym!
The stage was then set for a series of esoteric arguments over the correct name for Douglas-fir. During the period from 1897 until 1938, three different scientific names were used for one of the most important forest trees in all of North America: Pseudotsuga taxifolia (Lamb.) Britt. or more correctly Pseudotsuga taxifolia (Poir.) Britt. ex Sudw., Pseudotsuga douglasii (Sabine ex D. Don) Carr., and Pseudotsuga mucronata (Raf.) Sudw.10
In 1938, two English taxonomists skilled in botanical nomenclature, Thomas A. Sprague and Mary L. Green, concluded that the correct name was Pseudotsuga taxifolia, based not on the illegitimate Pinus taxifolia Lamb. (1803) but on Abies taxifolia Poit. (1805). They proposed Pseudotsuga taxifolia (Poit.) Rehder ex Sprague & Greene. Six years later the American forester and taxonomist Elbert Little,11 writing in the American Journal of Botany, noted that Sudworth proposed this same name 41 years earlier and concluded that the correct citation should be Pseudotsuga taxifolia (Poir.) Britt. ex Sudw. For a brief period of time, this was widely accepted, and the scientific name of Douglas-fir seemed to be finally settled.
In 1950, Joäo Manuel Antonio do Amaral Franco (born in 1921), a Portuguese botanist, once again published on the nomenclatural history of the scientific name of what by then was consistently known as Douglas-fir. Franco discovered two important facts. The first was that Abies taxifolia Poir. was itself a later homonyn and thus Pseudotsuga taxifolia (Poir.) Britt. ex Sudw., then in common use, could not be the correct name for the tree. The second and most important discovery was a previously unnoticed name in the French journal, Mémoires du Muséum d'Histoire Naturelle.
10. It is traditional in botanical nomenclature for the individual, or individuals, who name a plant to have their name associated with that plant's name. Often, the person's name is abbreviated. Scientific names come in two parts, the first of which is also in two parts. The binomial is a combination of a generic name and a specific epithet. Pseudotsuga is a generic name. The epithet modifies the generic name, identifying the species, variety, or other division of the genus. In the case of Douglas-fir, the correct epithet is menziesii. All binomials are in Latin or composed of words treated as if they were Latin; binomials are always in italics with the generic name capitalized and, by modern tradition, the specific epithet in lower case. The second part of a scientific name is its authorship. White oak, for example, was named by Carl Linnaeus (1707-1778) in 1753, the Swedish naturalist who began our modern system of nomenclature. The scientific name of white oak is Quercus alba L., the "L." being an abbreviation for Linnaeus. One can think of such a name as the "white oak named by Linnaeus." In the case of Douglas-fir, the authorship portion is more complex. Mirbel's name, abbreviated "Mirb." is placed in parenthesis. This informs the botanist that Mirbel proposed the specific epithet menziesii but placed it a genus other than Pseudotsuga – specifically, he associated the epithet with the generic name Abies. The name of the second person, Franco, is not abbreviated because it is relatively short. Franco's name follows Mirbel's but is outside the parenthesis. This informs the botanist that Franco transferred the epithet menziesii from Abies to Pseudotsuga. Occasionally the word "e"X – Latin for "from" – may be found between two authors' names, as in "Sabine ex D. Don." This is a special condition in which a botanist attempts to record the history of a name in its authorship. As noted already, it was Sabine who suggest that Don name the then Oregon pine for David Douglas, but it was Don who actually published the name. Thus Sabine suggested "douglasii" but Don put the name into print.
11. Elbert Luther Little, Jr., born in 1907, is today the dean of American dendrologists. Long associated with the United States Forest Service, he basically replaced Sudworth as the one person the United States government depended upon to render taxonomic judgments of the nomenclatural status of each name of the nation's trees. A prolific writer of numerous scientific articles and books, he has also written for the general public and especially American foresters. While now in his 90s and no longer active in systematic botany, he remains a valuable source of personal knowledge about America's forests. He has mapped, and seen, most of them. His 1953 and 1979 Check list of native and naturalized trees of the United States (including Alaska) remain important sources for both common and scientific names of our forest trees.