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..
Chrysanthemum segetum L. Sp. Pl. 889. 1753.
Annual, glabrous, 1 1/2° high or less. Leaves oblong to oblanceolate, the upper auriculate-clasping, the lower petioled, dentate, incised, or nearly entire, 3' long or less; heads about 1 1/2' broad; involucral bracts obtuse, scarious; rays obovate, yellow, emarginate; pappus a mere margin.
Waste grounds, New York, New Jersey, and in ballast about the seaports. Adventive from Europe.
Chrysanthemum coronarium L., also European, with yellow rays and bipinnatifid leaves, has been found in Ontario.
Matricaria Parthenium L. Sp. Pl. 890. 1753. C. Parthenium Pers. Syn. a: 462. 1807.
Perennial; stem puberulent or glabrate, much branched, 1°-2 1/2° high. Leaves thin, the lower often 6' long, petioled, or the upper sessile, pinnately parted into ovate or oblong, pinnatifid or incised segments; heads numerous, corymbose, slender-peduncled, 6"-10" broad; bracts of the depressed involucre lanceolate, rather rigid,keeled,pubescent, acute or acutish; rays 10-20, white, oval or obovate, spreading, mostly toothed, long-persistent; pappus a short toothed crown.
In waste places, New Brunswick and Ontario to New Jersey, Ohio, and in California, mostly escaped from gardens. Naturalized or adventive from Europe. Called also pellitory, wild camomile. Rays variable in length. Summer.
C. Balsamita L. Sp. Pl. Ed. 2, 1252. 1763.
Pyrethrum Balsamita Willd. Sp. Pl. 3: 2153. 1804.
Perennial, puberulent or canescent; stem much branched, 2°-4° high. Leaves oblong, obtuse, crenate-dentate, 1'-2' long, those of the stem mostly sessile, and often with a pair of lateral lobes at the base; heads numerous, corymbose, slender-peduncled, 5"-8" broad, or when rayless only 3" broad; bracts of the involucre narrow, obtuse, pubescent; rays 10-15, white, spreading; pappus a short crown.
Sparingly escaped from gardens, Ohio to Michigan, Ontario and Nova Scotia. Native of the Old World. Other English names are cost, alecost, ale-coast. Summer.