Herbs or subshrubs, annual, biennial, or perennial, glabrous or hairy. Stems usually erect or spreading to ascending, sometimes decumbent or ascending from decumbent base, unbranched or branched at base, throughout, or only in inflorescence. Leaves sometimes falling early, alternate or sometimes partially opposite or whorled; stipular glands present or absent; blade linear, linear-lanceolate, linear-oblanceolate, lanceolate, oblanceolate, elliptic, oblong, obovate, spatulate, or awl-shaped, margins glandular-toothed or entire, sometimes ciliate. Inflorescences usually panicles, racemes, or cymes, rarely thyrses or corymbs. Pedicels articulated or not. Flowers: sepals persistent or deciduous, 5, connate at base, equal or unequal in size, margins scarious, entire, ciliate, or toothed, glandular or not; petals 5, distinct or coherent at base, attached to filament cup at base, midway, or on or proximal to rim, blue, white, yellow, yellowish orange, orange, or salmon, rarely red or maroon, sometimes with darker bands near base, appendages absent or pouches formed on petal margins at base of claw; stamens 5; staminodes 0 or 5, as small deltate projections; pistil 5-carpellate, ovary 5-locular, or 10-locular by intrusion of false septa; styles 5, distinct or connate; stigmas capitate, linear, or clavate, wider than styles. Fruits capsules, usually 5-celled and dehiscing into 5 segments, sometimes each cell partially divided by incomplete or nearly complete false septum and dehiscing into 10 segments. Seeds 10, lenticular. x = 13, [15, 18].
Nearly worldwide, temperate and subtropical regions.
Species ca. 180 (37 in the flora).
C. M. Rogers (1963, 1964, 1968, 1982, 1984) published comprehensive studies of Linum in North America and Central America; he also studied Linum in South America (Rogers and R. Mildner 1976), southern Africa (Rogers 1981), and Madagascar (Rogers 1981b). This treatment draws largely on his work and follows his taxonomic arrangement, which is congruent, at least at the level of section, with the results in J. R. McDill et al. (2009). Species of Linum in the flora have been placed in three sections of the genus, out of a total of five sections worldwide.
|1||Petals yellow, sometimes with maroon at base.||Linum sect. Linopsis|
|1||Petals red, white, or blue.||> 2|
|2||Sepal margins not glandular-toothed; petals usually blue or red to maroon, rarely white.||Linum sect. Linum|
|2||Sepal margins (at least inner) glandular-toothed, petals white.||Linum sect. Cathartolinum|