9. E. Préslii, Guss. Smooth or with scattered hairs, ascending or erect (1–2° high); leaves oblique at the obtuse or slightly cordate base, ovate-oblong or oblong-linear, sometimes falcate, serrate (½–1½´ long), often with a red spot or red margins; stipules triangular; peduncles longer than the petioles, collected in loose leafy terminal cymes; appendages entire, larger and white, or smaller and sometimes red; pod glabrous, obtusely angled; seeds ovate, obtusely angled, wrinkled and tubercled (½´´ long), blackish. (E. hypericifolia of Man., not L.)—Common throughout the U. S. east of the plains.
§ 2. ZYGOPHYLLÍDIUM. Leaves opposite, on short petioles, not oblique, with stipular glands; stems dichotomously branched, erect; cymes terminal; involucres with 5 glands; seeds tuberculate.
10. E. hexágona, Nutt. Somewhat hairy (1° high or more); branches striate-angled; leaves linear-lanceolate, entire; involucre hairy without and within; glands with green ovate-triangular appendages twice their length; capsule smooth; seeds ovate.—Iowa to Tex., west to Col. and Montana.
§ 3. PETALÒMA. Uppermost leaves with conspicuous white petal-like margins, whorled or opposite, the others scattered; erect annuals, with leaves equal at base and entire, and with lanceolate deciduous stipules; involucres 5-lobed, in an umbel-like inflorescence.
11. E. marginàta, Pursh. Stem stout (2–3° high), erect, hairy; leaves sessile, ovate or oblong, acute; umbel with 3 dichotomous rays; glands of the involucre with broad white appendages.—Minn. to Mo., west to Col., also spreading eastward to Ohio, and frequently escaped from gardens, where it is often cultivated for its showy broadly white-margined floral leaves.
§ 4. TITHYMALÓPSIS. Only the uppermost leaves whorled or opposite; erect perennials, with entire leaves equal at base; stipules none; involucres mostly 5-lobed, in the forks of the branches and terminal; inflorescence umbelliform.
12. E. corollàta, L. Glabrous or sometimes sparingly hairy (2–3° high); leaves ovate, lanceolate, or linear, entire, obtuse; umbel 5- (3–7-) forked, and the forks again 2–3- (or rarely 5-) forked; involucres long-peduncled, with showy white appendages (appearing like petals), the lobes minute and incurved; pod slender-pedicelled, smooth; seeds thick (1´´ long or more), ash-colored, slightly uneven.—Rich or sandy soil, N. Y. and N. J. to Fla., west to Minn. and La., also adventive in Mass. July–Oct.
B. Glands of the involucre without petaloid appendages.
§ 5. POINSÉTTIA. Involucres in terminal clusters, 4–5-lobed, with few (or often solitary) cup-shaped glands; erect annuals, with variable, entire, dentate, or sinuate leaves, all or only the upper ones opposite; the uppermost often colored, especially at base; stipules small and glandular.
13. E. dentàta, Michx. Erect or ascending, hairy (1° high); leaves ovate, lanceolate, or linear, petioled, coarsely toothed (1–2´ long), only the lowest alternate, the upper often paler at base; involucres almost sessile, with 5 oblong dentate lobes, and one or sometimes more short-stalked glands; seeds ovate-globular, slightly tubercled.—Rich soil, Penn. to Tenn., Iowa, E. Kan., and southward. July–Sept.