186 



N. Ord. CONVOLVULACEJ5. 



Genus Exogonium,* Choisy. Choisy, in DC. Prod., ix, pp. 

 346-7. Species 8 or more, natives of the W. Indies and 

 tropical America. 



186- Exogonium Purga,f Benth., Plant.Hartweg.,p. 46 (1839). 



Jalap. 



fifyn. Ipomsea Purga, Hayne. I. Jalapa, Nutt. (non Pursh). Convol- 

 vulus Puvga, Wenderoth. C. Jalapa, Schiede (non Linn.). 



Figures. Nees, Supp.; Hayne, xii, tt. 33, 34; Berg & Sen., t. 5 a, b; 

 Bot. Mag., t. 4280 ; Zuccarini, PI. Nov., fasc. i, t. 12. 



Description. An herbaceous perennial twiner. Stems numerous, 

 slender, twisted and furrowed, twining, smooth, purplish, reaching 

 ] 2 feet or more in length, moderately branched, arising from the 

 crown of fleshy tubercular roots, which are nearly globular, tapering 

 below into a fibrous termination, reaching the size of an orange or 

 small turnip but usually smaller, brown and finely mottled or 

 spotted externally, white within. Leaves alternate, without 

 stipules, on thick stalks nearly as long as themselves, 4 or 5 

 inches long, deeply cordate at the base with pointed lobes, 

 attenuated at the apex, quite entire, smooth on both surfaces, 

 paler below, veiny. Flowers in small axillary cymes usually of 

 3 flowers, on long wiry twisted peduncles, pedicels with small 

 bracts at base, about half an inch long, thickened upwards. Calyx 

 short, ovoid, smooth, cut into 5 oblong, blunt, imbricate segments, 

 the two outer shorter, margins membranous. Corolla large, salver- 

 shaped, glabrous, the tube about 2 inches long, slender, slightly 

 wider above, again, contracted where it joins the limb, which is 

 nearly horizontal, about 2 \ inches across, somewhat undulated, of 5 

 broad truncate segments scarcely separated by a faint notch, 

 and marked down the centre by a tapering band, twisted in 

 aestivation, deep, dull, purplish-pink. Stamens 5, inserted near 



* Exogonium, from the stamens projecting out of the corolla, 

 f Purga, the Spanish name of ihe drug, from its action. 



