It, too, forms large tubers, which it stores full of plant food, but it so happens that this particular plant food is not fit for human food. We put it to quite another use. In fact, jalap is used as a medicine. It grows very luxuriantly at Jalapa, or, as the Mexicans spell it, Xalapa, in Mexico, and that is the way it gets its name of jalap.
In spite of its very disagreeable taste and beneficial effect upon sick people, the jalap is a lovely vine with beautiful deep pink flowers.
If you saw it growing along the eastern slopes of the Mexican mountains you would never suspect it of being a medicine plant, and you might not suspect it of being a convolvulus, since its flowers are flat instead of tubular in form.
Scammony.
Several members of the Convolvulus Family have the same medicinal properties as jalap, and one in particular, whose name is scammony, is very highly esteemed.
It has an uncommonly bad taste, and its swollen roots are brought all the way from Syria and Asia Minor, not because of their bad taste, but because of their power as a medicine. The scammony, like the jalap, is a pretty plant in spite of its bad-tasting, medicinal roots.
Most of the Convolvulaceæ have a milky, bitter juice,—even our pretty, harmless morning-glories,—and in the jalap and scammony this seems to be exaggerated in quality and quantity.
A few of the Convolvulaceæ manage to make woody stems and become shrubs instead of vines.
Two of these live on the Canary Islands, and their sap, instead of being nauseous and bad-smelling, has a delicate and delicious fragrance. People take the wood from root and stems and press out the oil to be used in making perfumery.