in botany: A genus of plants belonging to the class of didynamia, and order of gymnospermia; and in the natural system arranged under the 42d order, Verticillate. The upper lip of the corolla is arched; the lower lip reflexed, and the larger intermediate lacinia is margined. The stamens, after shedding the farina, are bent towards the sides. There are 17 species, the sylvatica, palustris, alpina, germanica, lanata, cretica, glutinosa, orientalis, palentina, maritima, ethiopica, hirta, canariensis, recta, annua, and arvensis. Four only are natives of Britain.

1. Sylvatica, hedge-nettle. The plant is hairy all over, erect, a yard high, and branched; the hairs are jointed. The flowers are of a deep red colour, six or eight in a whirl, which terminates in a long spike destitute of leaves. The leaves are heart-shaped, and grow on footstalks. The whole plant has a strong fetid smell. It grows commonly in woods and shady places, and flowers in July or August.

2. Palustris, clown's all-heal. The roots are white and tuberous. The stalk is branched at the bottom, and two or three feet high. The flowers are red or purple, from six to ten in a whirl, ending in a long spike. The leaves are fleshy, narrow, pointed, and in part surrounding the stem. This plant has a fetid smell and bitter taste, and is reckoned a good vulnerary. It grows on the sides of rivers and lakes, in low moist grounds, and sometimes in corn-fields.

3. Germanica, bale horsetail. The stem is downy, and about two feet high. The leaves are white, downy, wrinkled, and indented. The flowers are white, purplish within, and grow in multiformulous whirls. It grows in England.

4. Arvensis, corn-stachys, petty ironwort, or all-heal. The stalk is 10 or 12 inches high, square, branched, and hairy. The leaves are heart-shaped, obtuse, bluntly serrated, and less hairy. The calyx is hairy and fleshy, and deeply divided into five acute dents of equal length. The flowers are flesh-coloured, and grow from three to six in a whirl. The lower lip is trifid; the middle segment spotted with red, but not emarginated according to the character of the genus. It is frequent in corn-fields, and grows from June to August.