A Flora of North America: Containing Abridged Descriptions of All the Known Indigenous and Naturalized Plants Growing North of Mexico: Arranged According to The Natural System.

In 1820, American botanist, chemist, and physician John Torrey undertook the examination of the plants that had been collected around the headwaters of the Mississippi by David B. Douglass. During the same year, he received the collections made by Edwin James while with the expedition that was sent out to the Rocky Mountains under Major Stephen H. Long. His report was the earliest treatise of its kind in the United States that was arranged on the natural system. Torrey, in the meantime, had planned A Flora of the Northern and Middle United States, or a Systematic Arrangement and Description of all the Plants heretofore discovered in the United States North of Virginia, and in 1824 began its publication in parts, but it was soon suspended owing to the general adoption of the natural system of Antoine Laurent de Jussieu in place of that of Carl Linnaeus. In 1836, on the organization of the geological survey of New York, he was appointed botanist, and required to prepare a flora of the state. His report, consisting of two quarto volumes, was issued in 1843, and was for a long time the most comprehensive for any state in the United States. In 1838, he began with Asa Gray The Flora of North America, which was issued in numbers irregularly until 1843, when they had completed the Compositae, but new botanical material accumulated at such a rapid rate that it was deemed best to discontinue it.