CONVOLVULUS. herbaceous stalks growing about two feet long, which do not twine like the other sorts, but decline toward the ground, upon which many of the lower branches lie prostrate; they are garnished with spear-shaped leaves, which sit close to the branches: the footstalks of the flowers come out just above the leaves of the same joint, and at the same side of the stalks. They are about two inches long, each sustaining one large open bell-shaped flower, which in some is of a fine blue colour with a white bottom; in others they are pure white, and some are beautifully variegated with both colours. The white flowers are succeeded by white seeds, and the blue by dark-coloured seeds; which difference is pretty constant. 8. The soldonella, or sea-bindweed, styled also brassica marina, grows naturally on the sea-beaches in many parts of England, but cannot be long preserved in gardens. It hath many small white stringy roots, which spread wide and send out several weak trailing branches. These twine about the neighbouring plants like those of the common bindweed, garnished with kidney-shaped leaves like those of the lesser celandine. The flowers are produced on the side of the branches at each joint. They are of a reddish purple colour, and appear in July. They are succeeded by round capsules, having three cells, each containing one black seed. 9. The turpethum is a native of the island of Ceylon. This hath fleshy thick roots, which spread far in the ground, and abound with a milky juice that flows out when the roots are broken or wounded, and soon hardens into a resinous substance when exposed to the sun and air. From the root shoots forth many twining branches, which twist about each other, or the neighbouring plants, like the common bindweed. They are garnished with heart-shaped leaves that are soft to the touch, like those of the marshmallow. The flowers are produced at the joints on the side of the stalks, several standing together on the same footstalk: they are white, and shaped like those of the common great bindweed, and are succeeded by round capsules, having three cells containing two seeds each. 10. The jalapa, or jalap, used in medicine, is a native of Aleppo in Spanish America, situated between La Vera Cruz and Mexico. It hath a large root of an oval form, which is full of a milky juice; from which come out many herbaceous twining stalks rising eight or ten feet high, garnished with variable leaves; some of them being heart-shaped, others angular, and some oblong and pointed. They are smooth, and stand upon long footstalks: the flowers are shaped like those of the common greater bindweed, each footstalk supporting only one flower.
Culture. The first and second sorts are propagated by seeds, which must be sown on a border of light earth. The second sort must have some tall stakes placed near them for their branches to twine about, otherwise they will spread on the ground and make a bad appearance. The third sort is annual, and must be propagated by seeds sown on a hot-bed in the spring, and towards the end of May they should be planted out in warm borders, and treated in the same manner with the former. The fourth species is sometimes propagated in this country. The roots must be planted on a hot-bed in the spring; and if the plants are covered in bad weather with glasses, they will
produce flowers and some small bulbs from the joints of the stalks: but if they are exposed to the open air they seldom grow to any size. The fifth is propagated by laying down the young shoots in the spring, which generally put out roots in three or four months: they may then be taken from the old plants, and each placed in a separate pot, which is to be set in the shade till they have taken new root; after which they may be placed with other hardy green-house plants till autumn, when they should be removed into the green-house, and afterwards treated in the same manner as myrtles and other green-house plants. The turbith and jalap are too tender to live in this country, unless they are constantly kept in a stove. The other species require no particular directions for their cultivation.
Uses. The root of the first sort is a very acrid purgative to the human race, but is eaten by hogs in large quantities without any detriment. The inspissated juice of this might probably answer the purposes of scammony, which at present is imported from Aleppo at a considerable annual expence. The inspissated juice of the second species is used in medicine as an acrid purgative; as are also the roots of JALAP and TURPETH. The soldanella has likewise been used with the same intention. Half an ounce of the juice, or a drachm of the powder, is an acrid purge. The leaves applied externally are said to diminish dropical swellings of the feet.