water-cresses, in botany: A genus of plants belonging to the class of tetradytania, and to the order of filiqueae; and in the natural system ranged under the 39th order, filiqueae. The filiquea, or pod, opens with valves somewhat straight. The calyx and corolla are expanded: There are 29 species, of which eight are natives of Britain; the nafturtium, or common water-cress; sylvestre, water-rocket; amphibium, water-radish; terrestris, annual water-radish; monentis; sophia, flixweed; irio, broad-leaved hedge-mustard.
1. The nafturtium grows on the brink of rivulets and water ditches. The leaves have from 6 to 8 pair of smooth succulent and sessile pinnae; the flowers are small and white, and grow in short spikes or tufts. The leaves of water-cresses have a moderately pungent taste, emit a quick penetrating smell, like that of mustard seed, but much weaker. Their pungent matter is taken up both by watery and spirituous menstrua, and accompanies the aqueous juice, which issues copiously upon expression. It is very volatile, so as to arise in great part in distillation with rectified spirit, as well as with water, and almost totally to exhale in drying the leaves, or infusing by the gentlest heat to the confidence of an extract, either the expressed juice, or the watery or spirituous tinctures. Both the infused juice, and the watery extract, discover to the taste a saline impregnation, and in keeping throw up crystalline efflorescences to the surface. On distilling considerable quantities of the herb with water, a small proportion of a subtile volatile very pungent oil is obtained.
Water-cresses obtain a place in the Materia Medica for their antiscorbutic qualities, which have been long very generally acknowledged by physicians. They are also supposed to purify the blood and humours, and to open visceral obstructions. They are nearly allied to scurvy-grass, but are more mild and pleasant, and for this reason are frequently eaten as salad. In the pharmacopoeias the juice of this plant is directed with that of scurvy-grass and Seville oranges; and Dr Cullen has remarked, that the addition of acids renders the juices of the plantae filiqueae more certainly effectual, by determining them more powerfully to an acetic fermentation.
2. Silvestre, or water-rocket. The stem is weak, branched, and above a foot high. The leaves are pinnated; the pinnae lance-shaped, and ferrated; the flowers small, and yellow; and grow frequently in shallow water.
3. Amphibium, or water-radish. The stem is firm, erect, and two or three feet high; the leaves are pinnatifid, and ferrated; the flowers are yellow, and in spikes; the pods are somewhat oval, and short. It grows in water.
4. Terrestre, or land-rocket. The leaves are pinnatifid; the pods are filled with seed; the root is annual, and white; the stem is angular, red-green, and smooth.
5. Murale, or wall-rocket. The stems are rough, and about eight inches high; the leaves grow on foot-stalks, lance-shaped, smooth, finuated, and ferrated; the flowers are yellow; the pods a little compressed, and slightly carinated. It grows on sandy ground in the North, Anglesea, &c.
6. Monentis, or yellow rocket. The stem is smooth, and about 6 or 8 inches high; the leaves are pinnatifid; the pinnae remote, generally 7 pair; the flower is yellow; the petals entire; the calyx is closed. It grows in the Isle of Man.
7. Irio, broad leaved rocket, or hedge mustard; the stem is smooth, and about two feet high; the leaves are broad, naked, pinnated, and halberd shaped at the end; the flowers are yellow, and the pods erect. It grows on waste ground.
8. Sophia, flixweed. The stem is firm, branched, and two or three feet high; the leaves are multifid; the segments are narrow; the flowers are yellow; the petals much less than the calyx; the pods are long, stiff, curved, without style, and erect; the seeds are minute, and yellow. It grows on walls, waste ground, &c.