This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", 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..
Hypericum cistifolium Lam. Encycl. 4: 158. 1797. H. sphaerocarpum Michx. Fl. Bor. Am. 2: 78. 1803. Simple or branching, erect or ascending from a somewhat woody perennial base, 1°-2 1/2° high; stems 4-angled. Leaves oblong or linear-oblong, obtuse, 1 1/2'-3' long, 3"-6" wide, often with smaller ones in the axils; cymes terminal, several or many-flowered, naked; flowers sessile or nearly so, 5"-8" broad; sepals linear, lanceolate or ovate, much shorter than or equalling the petals; stamens numerous, distinct; styles 3, united below; capsule strictly I-celled, globose or ovoid-conic, 2"-2 1/2" long; seeds larger than in related species, rough-pitted.
Hypericum BissÚllii Robinson, known only from Southington, Connecticut, has smaller leaves, the cyme leafy-bracted, the sepals very unequal.
Straggling and branching, decumbent, 6-20' high; branch-lets slightly angled. Leaves linear or linear-lanceolate, 8"-2o" long, 1"-2" wide, acute or obtusish, spreading or ascending, with smaller ones clustered in the axils; cymes terminal, leafy, few-several-flowered; pedicels about i" long; flowers nearly 1' broad; sepals foliaceous, lanceolate or ovate, acute or acuminate, nearly or quite as long as the oblique pointed petals; stamens numerous, distinct; styles 3, united below; capsule ovoid-conical, coriaceous, 3"-4" long, I-celled; seeds rugose.
H. ellipticum Hook. Fl. Bor. Am. 1: no. 1830.
Herbaceous, perennial; stem somewhat 4-angled, simple or with few branches, erect, 8'-2o' high. Leaves thin, spreading, elliptic or oval, obtuse, sessile, narrowed at the base or partly clasping, 8"-15" long, 3"-5" wide; cymes terminal, few-flowered, leafless but bracted; flowers pale yellow, nearly sessile, 5"-7" broad; sepals spreading, oblong or oblanceolate, slightly shorter than the petals; styles 3, united below; stamens numerous; capsule ovoid-globose, I-celled, about 2" long; seeds striate; sepals and petals sometimes 4.
Slender, herbaceous, erect or ascending, simple, or branched above, 1°-2 1/2° high, the stem and branches 4-angled. Leaves ascending or erect, oblong-lanceolate to elliptic, acute or obtuse, 15" long or less, 2"-7" wide, sessile; cyme terminal, ample, compound, bracted; pedicels 1/2"-2" long; flowers numerous, copper-yellow, alternate, 4"-6" broad; sepals foliaceous, ovate or lanceolate, keeled, more or less shorter than the petals; styles 3, distinct; stigmas capitate; capsule I-celled, 2" long, enclosed by the sepals.
In low grounds. New Jersey and Pennsylvania to Illinois, south to Florida and Tennessee. July-Sept.