Britton & Brown - An illustrated flora of the northern United States… 03 BHL-102870 1913
From Offene Naturführer
Britton, N. L. & Brown, A. 1913: An illustrated flora of the northern United States, Canada and the British possessions: from Newfoundland to the parallel of the southern boundary of Virginia and from the Atlantic Ocean westward to the 102nd meridian. 2. Auflage. Bd. 3, Charles Scribner’s sons, New York (2nd ed., rev. and enl.; v.3. Gentianaceae to Compositae, Gentian to Thistle – https://www.biodiversitylibrary.org/item/102870).