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 perennial often paniculately or corymbosely branched herbs. Leaves alternate or occasionally opposite, without stipules but sometimes with stipular glands, mostly narrow, entire or serrulate, sometimes ciliate or glandular-margined. Sepals 5, persistent or deciduous, all of them or only the inner ones with gland-tipped teeth Petals 5, yellow or white, unappendaged but sometimes pubescent within near the entire base. Stamens 5; filaments united at the base, the free portions abruptly or gradually dilated at the base, not accompanied by staminodia, or rarely with a short staminodium in each sinus. Gynoecium 5-carpellary, or rarely 2-carpellary, sometimes cartilaginous at the base; styles filiform, distinct or united; stigmas distinct, terminal, capitate. Capsule ovoid or depressed, 5-ceHed, or rarely 2-celled and with firm septa, or completely or incompletely 10-celled by false septa, the carpels not ribbed on the back. Seeds flattened, often lunate. [Greek, referring to the medicinal qualities of some of the species.]
About 70 species of wide geographic distribution. Type species: Linum cathŕrticum L. Styles distinct.
Staminodia wanting; plants perennial; corolla yellow.
Sepals entire at maturity, the inner ones sometimes roughened by the bases of the deciduous
Stem paniculately branched; outer sepals short (1"-1 1/4" long); stem-leaves mostly
Stem corymbosely branched; outer sepals long (1 1/2"-1 3/4" long); stem-leaves mostly
Sepals, either those of both series, or those of the inner or the outer series, glandular-toothed.
Capsules spheroidal, depressed at the apex.
Capsules ovoid; pointed at the apex.
Staminodia present; plants annual; corolla white.
Styles more or less united.
Sepals persistent; capsules without thickenings at the base
Sepals deciduous; capsules with cartilaginous thickenings at the base.
Outer sepals slightly exceeding the capsules; false septa of the capsule slightly thickened.
Outer sepals greatly exceeding the capsule; false septa of the capsule thickened for about
one half their width.