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..
Coreopsis verticillata L. Sp. P1. 907. 1753.
Perennial; stem stiff, much branched, slender, leafy, 1°-2° high. Leaves sessile, glabrous, 2-3-ternately dissected into linear-filiform entire segments; heads numerous, 1'-1 1/2' broad; involucre hemispheric, or short-cylindric in fruit, glabrous, its outer bracts linear, obtuse, commonly somewhat shorter and much narrower than the ovate-oblong inner ones; rays 6-10, yellow, spatulate-oblong, obtuse; disk dull yellow; achenes oblong, narrowly winged, 2" long; pappus of 2 short teeth.
In dry soil, Maryland to South Carolina, Kentucky, Nebraska and Arkansas. Apparently erroneously recorded from farther north. June-Sept.
Coreopsis delphinifolia Lam. Encycl. 2: 108. 1786.
Perennial; stem glabrous, branched above, rather slender, 1°-3° high. Leaves sessile, 1-2-ternately partly into linear or linear-lanceolate segments, which are 1'-2' long, 1"-3" wide; heads several or numerous, 11/2'-2' broad; involucre hemispheric, its bracts glabrous, the outer linear-oblong, obtuse, shorter than or equalling the ovate-oblong inner ones; rays 6-10, yellow, entire; disk brown; achenes oblong to oval, narrowed at the base, narrowly winged; pappus of 2 short teeth.
Calliopsis cardaminefolia DC. Prodr. 5: 568. 1836. C. cardaminefolia T. & G. Fl. N. A. 2: 346. 1842.
Annual; stem glabrous, branched, 1°-21/2° high. Basal leaves petioled, 2'-4' long, 1-2-pinnately parted into oblong or oval obtuse segments, the petioles sometimes slightly ciliate; stem leaves distant, sessile, or nearly so, pinnately parted into linear segments, or the uppermost entire; heads 8"-12" broad, slender-peduncled; involucre hemispheric, its inner bracts brown, ovate or ovate-lanceolate, obtuse or obtusish, scarious-margined, much longer than the lanceolate obtusish outer ones; rays 4-8, yellow with a brown base, 3-toothed; achenes oval, 1"-1 1/2" long, winged, smooth, or slightly papillose; pappus of 2 minute awns, or none.
In moist soil, Kansas to New Mexico, Louisiana and northern Mexico. May-Oct.
Coreopsis Atkinsoniana Dough, a northwestern species, with linear leaf-segments and very narrowly winged achenes, ranges eastward into North Dakota.
Annual; stem glabrous, branched, 1°-3 1/2° high. Leaves 1-2-pinnately divided into linear, obtusish, mostly entire segments, or the uppermost linear and entire, the lower petioled; heads slender-peduncled, 10"-12" broad, or in cultivation much broader; involucre hemispheric, its inner bracts brown, ovate or oblong, obtuse or acute, scarious-margined, 3-5 times as long as the obtuse outer ones; rays 6-10, cuneate, yellow with a brown base or brown all over; achenes linear or linear-oblong, about 1" long, wingless; pappus a mere border, or none.