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..
Stem usually freely branching, 4-angled, 1°-2 1/2° high, the branches all opposite. Leaves linear, linear-oblong, or lanceolate, obtuse. 1/2'-1 1/2' long, the lower commonly shorter and broader, the uppermost small and bract-like; flowers white, 6"-9" broad, usually very numerous in corymbed cymes; pedicels mostly short, the central flowers of the cymes often nearly sessile; calyx-lobes linear, not more than one-half the length of the corolla; corolla-segments spatulate-oblong; anthers recurved or coiled; style 2-parted; capsule oblong, about 3" high.
In dry or moist soil, Virginia to Florida. May-Sept.
Chironia angularis var. angustifolia Michx. Fl.
Stem slender, branched above, slightly 4-angled, 1°-2° high, the branches all opposite. Leaves linear, linear-oblong, or linear-lanceolate, obtuse, or the upper acute, sessile, 1-2' long, the uppermost small and bract-like; flowers pink with a yellowish or greenish eye, few in the racemed or short-corymbed cymes, or solitary at the ends of the branches, about 1' broad; calyx-lobes linear, usually more than one-half the length of the corolla; corolla-segments obovate-oblong; style 2-cleft to about the middle; capsule oblong, 3"-4" high.
In dry or moist soil, Indiana to Louisiana, east to North Carolina and Florida. May-Sept.
Chironia angularis L. Sp. Pl. 190. 1753. S. angularis Pursh, Fl. Am. Sept. 137. 1814.
Stem usually rather stout and much branched, sharply 4-angled, 2°-3° high, the branches all opposite or the lowest rarely alternate. Leaves ovate, acute at the apex, cordate-clasping at the base, 9'-18" long, or the lower oblong and obtuse, those of the branches smaller; flowers rose-pink, with a central greenish star, occasionally white, 1'-1 1/2' broad, usually solitary at the ends of the branches; calyx-lobes linear, one-half the length of the corolla, or less; corolla-segments obovate; style 2-cleft; capsule oblong, about 3" high.
In rich soil, often in thickets, New York and Pennsylvania to western Ontario, Michigan, Florida, Arkansas, Oklahoma and Louisiana. Bitter clover. Pink-bloom. American centaury. July-Aug. Flowers fragrant.
Stem somewhat 4-angled, freely branched, 6'-12' high, the branches alternate, or the lowest sometimes opposite. Leaves oblong or some of them slightly obovate, obtuse or acute, 3-nerved, 1'- 2' long, narrowed to the sessile base or the lower into petioles; flowers usually few, solitary at the ends of the branches or peduncles, 1- 1 1/2' broad; calyx-lobes linear or spatulate, leaf-like, longer than the spatu-late segments of the pink rose-purple or whitish corolla; style 2-parted, capsule ovoid-oblong, 3"- 4" high.
In moist soil, Virginia to Florida, near the Coast, Cuba; Santo Domingo. June-Aug,