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..
Perennial or annual, mostly erect and branching herbs, with alternate, dentate, incised or dissected leaves, and large, usually long-peduncled heads of both tubular and radiate flowers, or rays rarely wanting. Involucre hemispheric or depressed, its bracts appressed, imbricated in several series, the outer shorter. Receptacle flat, convex or hemispheric, naked. Ray-flowers pistillate, fertile, the rays white, yellow or rose-colored, entire or toothed. Disk-flowers perfect, fertile, their corollas with terete or 2-winged tubes and 4-5-cleft limbs. Anthers obtuse and entire at the base. Style-branches of the disk-flowers truncate, penicillate. Achenes angled or terete, 5-10-ribbed, those of the ray-flowers commonly 3-angled. Pappus none, or a scaly cup. [Greek, golden-flower.]
About 100 species, of wide geographic distribution in the northern hemisphere. Besides the following, 2 others occur in northwestern arctic America. Type species: Chrysanthemum coro-narium L.
Heads large, few or solitary at the ends of the stem or branches. Rays white.
Stem leaves linear-spatulate, pinnately incised: weed.
1. C. Leucanthemum.
Stem leaves cuneate-spatulate, toothed or lobed above; arctic.
2. C. arcticum.
3. C. segetum.
Heads numerous, small, corymbose; plants ecsaped from gardens. Leaves pinnatifid, the segments incised.
4. C. Parthenium.
Leaves oblong, serrate.
5. C. Balsamita.
C. Leucanthemum L. Sp. Pl. 888. 1753. Leucanthemum vulgare Lam. Fl. Fr. 2: 137. 1778.
Perennial; stems glabrous, or sparingly puberulent, simple or little branched, 1°-3° high, often tufted, the branches nearly erect. Basal leaves obovate, oblong, or spatulate, coarsely dentate, incised or pinnatifid, narrowed into long slender petioles; stem leaves mostly sessile and partly clasping, 1-3' long, linear-spatulate or linear, pinnately incised or toothed, the uppermost very small and nearly entire; heads few or solitary, 1'-2' broad, on long naked peduncles; rays 20-30, white, spreading, slightly 2-3-toothed; bracts of the involucre oblong-lanceolate, obtuse, mostly glabrous, with scarious margins and a brown line within the margins; pappus none.
In pastures, meadows and waste places, common throughout our area as a weed, but less abundant in the south and west. Bermuda. Naturalized from Europe. Native also of Asia. Other English names are dog-, bull-, butter-, big-, midsummer-, moon-, horse-, poorland- or maudlin-daisy; dutch morgan, moon-flower, moon-penny, great white ox-eye, poverty-weed, white man's-weed, herb margaret; bull's-eye daisy. Sheriff-pink. Dog-blow. Rays rarely short and tubular. Disk bright yellow. May-Nov.
Chrysanthemum arcticum L. Sp. Pl. 889. 1753. Leucanthemum arcticum DC. Prodr. 6: 45. 1837.
Similar to the preceding species, but somewhat fleshy, lower, seldom over 1 1/2° high. Leaves cuneate-spatulate, 1 1/2'-3' long, crenate or cleft at the apex, narrowed into a long tapering entire base, or the lower into slender petioles, slightly clasping at the base, the uppermost few, small, linear and nearly entire; heads solitary or few, long-peduncled, 1'-2' broad; rays 20-30, white; bracts of the involucre oblong, obtuse, brown, or with broad brown scarious margins, usually pubescent; pappus none.
Coast of Hudson Bay to Alaska. Also in arctic Europe and Asia. Summer.