Several members of the order are used medicinally for the strong purging properties of the milky juice (latex) which they contain; scammony is the dried latex from the underground stem of Convolvulus Scarnmonia, a native of the Levant, while jalap is the product of the tubercles of Exogonium Purga, a native of Mexico.
This kind of jalap, the Purga de Sierra Gorda of the Mexicans, was traced by Hanbury to I pomaea simulans.
Jalap Plant (Exogonium) - A graceful perennial trailing plant, none more beautiful among climbing plants than E. purga, and of its hardiness there can be little doubt.