This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", 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..
Slender usually branched annual glabrous herbs, with opposite leaves, and rather large blue or white flowers in terminal narrow racemes or panicles, or solitary at the ends of the slender peduncles. Calyx deeply 4-5-parted; segments narrow, often unequal. Corolla rotate, 4-5-parted; lobes vate or lanceolate, convolute, acute, with a pair of narrow appendages at the base. Stamens 4 or 5, inserted on the corolla-tube near its base; filaments slender or filiform; anthers ovate, sagittate, straight. Ovary 1-celled; ovules numerous; style none; stigma decurrent along the sutures of the ovary. Capsule 2-valved. Seeds small and numerous. [Greek, referring to the lateral stigmatic surfaces.]
About 7 species, of the colder parts of the northern hemisphere, only the following typical one in North America.
Swertia rotata L. Sp. Pl. 226. 1753.
Pleurogyne rotata Griseb. Gent. 309. 1839.
Stem erect, usually 6'-15' high, sometimes lower, simple, or with nearly erect branches. Leaves linear to lanceolate, 1/2'-2' long, 1 "-2" wide, or the basal spatulate or oblong. shorter and sometimes broader; sepals narrowly linear to lanceolate, about the length of the lanceolate to oblong-lanceolate corolla-segments which are 4"-7" long; capsule narrowly oblong.
Quebec, Greenland and Labrador to Alaska, south in the Rocky Mountains to Colorado. Recorded from the White Mountains of New Hampshire. Also in Europe and Asia. Summer.