This plant is one of the most anciently cultivated plants, found in Neolithic and Roman beds in Britain, Capsules and seeds of flax are common at Redhill, suggesting the bundles were steeped there. It was cultivated in Neolithic times. It occurs to-day where flax is cultivated either for oil or fibre, and has been so for 4000 to 5000 years in Mesopotamia, Assyria, Egypt, being still wild in the district between the Persian Gulf, Caspian Sea, Black Sea.

The early cultivation of this plant shows that it has been used in the weaving of textiles for a long period, and as its occurrence to-day is merely an indication of its escape from cultivation its habitat is always (in Britain) an artificial one. It is found on waste ground, in offal yards, millyards, docks, and granaries, and generally in and about towns where the seeds are liable to dispersal, or where canals and railways assist in the accidental scattering of seeds.

Flax has a characteristic habit of its own, being usually erect and single-stemmed. It has narrowly elliptical alternate leaves, which are ascending and linear. It is branched above, and smooth, the leaves close, without order, and 3-nerved.

The flowers, in a panicle, are blue and large. The 5 sepals are egg-shaped, acute, keeled, 3-veined, and the 5 petals are notched.

The capsule is smooth within, rounded, with 5 valves, and blunt, with a sharp point at the tip. The seeds are glossy, flattened at the side, the pods opening elastically.

It is often 18 in. high. The flowers bloom in June and July. It is annual.

Flax is like Purging Flax in the position of the honey glands, and the anther stalks are united below and form a fleshy ring in the hollow of the ovary, secreting drops of honey, which enlarge and reach the sepals below, from 5 glands on the outer surface opposite the stamens. The petals, which are much larger and blue, are attached to this fleshy ring just above the honey glands, and alternate with the stamens, the lower halves of the petals touching, becoming narrow at the base, and leaving a round opening just above the honey gland. The 5 anthers empty their pollen at the same time as the stigmas are ripe, and as the stigmas are on the same level, they become dusted with pollen, though the anthers are at first some distance from the stigmas, and thus avoid self-pollinating the plant. When a visitor comes from another flower and inserts its proboscis between the stigmas and anthers it cross-pollinates the flower, but if it approaches from outside it presses the anthers against the stigma and self-pollinates it. In the absence of insects the stamens bend inwards.

The visitors are Hymenoptera (Apidae, Apis mellifica, Halictus cylindricus) and Lepidoptera Silver Y Moth (Plusia gamma).

The seeds of Flax are dispersed by the plant's own agency. The fruit is 5-celled, and divided into 2 chambers occasionally. The outer seed coat swells when moistened and glues the seeds to the ground. When ripe and dry the capsule opens by 10 slits, and the seeds are dispersed round the parent plant.

It is more or less a lime-loving plant, growing on a lime soil in chalk and limestone districts, but it is also at home on sand and gravel, which are also largely associated with both formations.

The fungi Flax rust, Melampsora lini, and Flax wilt, Fusarium lini, attack Flax.

The beetles Aphthona euphorbae, A. virescens, Melolontha vulgaris, and the moths Silver Y Moth (Plusia gamma), Broom Moth (Mamestra pisi), Sword-grass (Calocampa exoleta), feed upon it.

Linum, Theophrastus, is the Greek linon. Flax is cognate with the German flachs, and may be from the Latin filum, a thread, filare, to spin. The second Latin name refers to its extraordinary usefulness to man. It is llin in Welsh, lion in Gaelic.