544 CONTOLVULACEiE. 



climates. The order has been divided into two sub-orders : — 1. Oon- 

 Tolvulese, true Bindweeds, leafy plants, with the coroUine tube not 

 scaly, embryo curved, cotyledons conspicuous. 2. Cusoutese, Dodders, 

 leafless parasites, having scales on the coroUine tube, embryo spiral 

 and filiform (fig. 598, p. 335), cotyledons inconspicuous. There are 

 51 genera and upwards of 740 species. Examples — Convolvulus, 

 Ipomoea, Exogonium, Dichondra, Ouscuta. 



The order is characterised generally by the presence of an acrid 

 juice in the roots, which has purgative properties. On this account 

 several of the plants are used medicinally. The old genus Convolvulus 

 has been split into various genera, such as Ipomxa, Exogonium, Phar- 

 hitis, Batatas, Quamoclit, Calonyction, and Lepistemon, according to 

 the form of the corolla, the exsertion or inclusion of the stamens, the 

 form and nature of the stigma, and the structure of the ovary. Exo- 

 gonium Purga (Ipomxa Purga) is the Jalap plant, a native of the 

 eastern declivities of the Mexican Andes, which grows well in this 

 country, requiring only the protection of a frame during winter. The 

 plant flowered regularly for many years in a cold frame in the Edin- 

 burgh Botanic Garden. It has been introduced on the Neilgherry hiUs, 

 South India. The root-stock is the officinal part. It has a roundish 

 tuberous form, is black externally, white and milky within, and varies 

 in size from that of a walnut to that of a moderate-sized turnip. It 

 contains a resin, in which its active properties reside. It is used in 

 the form of powder and tincture, as an active irritant cathartic. Ipo- 

 mcea Jalapa yields Mechoacan root, which has purgative properties. 

 I. Orizahensis supplies a kind of Jalap, the Purgo macho of the Mexi- 

 cans ; while /. simularis furnishes Tampico Jalap. The root of Con- 

 volvulus Scammonia yields a gummy resinous exudation, which consti- 

 tutes medicinal Scammony. The plant grows abundantly in Greece, 

 the Grecian Islands, and various parts of the Levant. The plant 

 succeeds well in a cold frame in the Edinburgh Botanic Garden. The 

 Jalap and Scammony plants flower in the open border in the garden. 

 Scammony is procured by cutting the root across, and collecting the 

 milky juice, which soon concretes. The drug is imported into this 

 country from Smyrna. Its active principle is a resin. It is used 

 medicinally as a drastic purgative, in the form of powder, pill, and 

 extract. A spurious kind of Scammony has been prepared from the 

 Tooi oi Convolvulus (Galystegia) sepivm; and several plants belonging 

 to the natural order Asclepiadacese yield a purgative exudation, which 

 has been used under the names of Montpellier and Bourbon Scammony. 

 The roots of some of the plants do not possess purgative qualities, and 

 have been used as articles of food. Batatas edulis (Convolvulus Bata- 

 tas) yields the sweet Potato, which contains much saccharine and 

 amylaceous matter, and is used as food in tropical countries. The 

 plant is reared in Carolina, Japan, and China, and succeeds within an 



