Jalap n. : The tubers of the Mexican plant Ipomoea purga (or Exogonium purga), a climber much like the morning-glory. The abstract, extract, and powder, prepared from the tubers, are well known purgative medicines. Other species of Ipomoea yield several inferior kinds of jalap, as the I. Orizabensis, and I. tuberosa.

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Taxonomy
Jalap, drug, free encyclopedia, plant, Vera Cruz, appearance, Mexican, search, tuberous roots, declivities, elevation, above sea level, neighbourhood, eastern slope, Europe, 17th century, city, botanical source.

Defination from the web:
Jalap is a cathartic drug consisting of the tuberous roots of Ipomoea purga, a convolvulaceous plant growing on the eastern declivities of the ... Jalap has been known in Europe since the beginning of the 17th century, and derives its name from the city of Xalapa in Mexico, near which it ...