saw wort, in botany: A genus of plants belonging to the class of syngenesia, and to the order of polygama aequalis. In the natural system it is ranged under the 49th order, Composita. The calyx is subcylindrical, imbricated; the scales of it pointed, but not spinous. There are 15 species: The tinctoria, alpina, arvensis, coronata, japonica, salicifolia, multiflora, noveboracensis, prealta, glauca, squarrosa, scariofa, spicata, amara, and centauroides. The three first species are British.

1. The tinctoria is distinguished by a serrated stem erect and slender, branched at the top, and three feet high. The leaves are smooth, pinnatifid, and serrated: The flowers are purple, in umbels, and terminal. The down of the seed is glossy, with a brown or gold tinge. It grows in woods and wet pastures. It dyes cloth of an exceeding fine yellow colour, which stands well when fixed with alum. Goats eat this plant; horses are not fond of it; cattle, swine, and sheep, leave it untouched. 2. The alpina, or mountain saw-wort. The root and stem are woody; the latter being from one to two feet high. The leaves are numerous, triangular, long, pointed, substantial, dark green above, white beneath, and serrated, with round intervals between the teeth, on footstalks. The flowers are purple. The scales of the calyx are very short and downy. It grows on high mountains, and flowers commonly in July or August. 3. The arvensis, corn saw-wort, or way-thistle. The stem is generally erect, branched, and two or three feet high. The leaves are sinuated, serrated, and spinous; those above being almost entire. The flowers are of a pale purple; the down is very long. This plant grows in cultivated grounds and byways, and flowers in July or August. When burned it yields good ashes for making glass or fixed alkali.