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..
Annual or biennial, glabrous, stout, glaucous. Stem usually erect, stout, 8-30 tall, mostly simple below, umbellately branched above; leaves numerous, the lower scattered, those subtending the umbel verticillate, the lower linear, reflexed, the upper lanceolate or linear-lanceolate, l 1/2'-5' long, entire, sessile, subcordate at the base; bracts opposite, ovate or ovate-lanceolate, truncate or sub-cordate; involucres 2 1/2" long, bearing 4 crescent-shaped unappendaged glands prolonged into short horns; capsule subglobose, 5"-6" in diameter, its lobes rounded; seeds oblong-ovoid, 2V-3" long, terete, usually wrinkled.
1814. Tithymalus obtusatus Kl. & Garcke, Abh. Akad. Ber. 1859: 69.
Annual, yellowish green, glabrous. Stem slender, erect or assurgent, 1°-2° high, strict, branched above, topped by a 3-rayed umbel; branches simple or forked; leaves, except the whorl, subtending the umbel, scattered, spatu-late-oblong, obtuse, serrulate to below the middle, sessile, the base slightly auricled; involucres short-peduncled, 1/2' long, bearing 4 stalked unappendaged glands; capsule subglo-bose, nearly 2" in diameter, with elongated warts, the lobes rounded; seeds lenticular, oblong, or orbicular-oblong, dark brown, faintly reticulated.
Euphorbia platyphylla L. Sp. Pl. 460. 1753. T. platyphyllus Hill, Hort. Kew. 172/4. 1768.
Annual, glabrous or nearly so. Stems mostly erect, slender, 4-20' high, terete, often reddish, topped by a usually 5-rayed umbel; the branches forked or umbellately branched; leaves except the whorl at base of the umbel, scattered, oblong or spatulate-oblong, io"-is" long, acute, serrulate, sessile, the base slightly auricled; bracts triangular-ovate or reniform, mucronate, often entire; involucres very thin, campanulate, nearly 1" long, sessile, bearing 4 sessile glands without appendages; capsule subglobose, about 2" in diameter, with depressed warts, the lobes rounded; seeds lenticular, oblong or nearly orbicular, smooth, brown.
Along the shores of the St. Lawrence River and the Great Lakes, west to Manitoba. Naturalized from Europe. June-Sept.