Ipomoea purga (Wender.) Hayne

Wood, John R. I., Munoz-Rodriguez, Pablo, Williams, Bethany R. M. & Scotland, Robert W., 2020, A foundation monograph of Ipomoea (Convolvulaceae) in the New World, PhytoKeys 143, pp. 1-823 : 1

290. Ipomoea purga (Wender.) Hayne , Getreue Darstell. Gew. 12: 5. 1833. (Hayne 1833: 5)

Convolvulus purga Wender., Pharm. Central-Blatt 1: 457. 1830. (Wenderoth 1830: 457). Type. MEXICO. Veracruz, Chiconquiaco, Schiede s.n. (lectotype NY00318915, designated by McDonald 1987c: 55, isolectotypes BM, GH, K, P).

Exogonium purga (Wender.) Benth. , Pl. Hartw. 46. 1840. (Bentham 1839-57: 46).

Batatas purga (Wender) Peterm., Pflanzenreich , ed. 1: 497, t. 132, fig. 750. 1838-1845. (Petermann 1838-1845: 497).

Ipomoea jalapa Nutt. in Coxe , Journ. Am. Med. Sci. 5: 305. 1829 [pub.1830]. (Coxe 1830: 305), nom. illeg. non Ipomoea jalapa (L.) Pursh (1814). Type. Plant from Xalapa [Veracruz], cultivated in the United States. (lectotype t. 1 (p. 306A) in Coxe (1830), designated here).

Ipomoea schiedeana Zucc. , Flora 14 (2): 801. 1831. (Zuccarini 1831: 801). Type. MEXICO. Veracruz, Chiconquiaco, Schiede s.n. (BM, GH, K, M?.NY, P).

Ipomoea jalapa Schiede & Deppe ex G. Don , Gen. Hist. 4: 271. 1838. (Don 1838: 271), nom. suerfl. et illeg. non Ipomoea jalapa (L.) Pursh (1814). Based in part on I. purga (Wender.) Hayne and in part on I. schiedeana Zucc.

Convolvulus officinalis Pelletan, J. Chim. Med. 10: 6. 1834. (Pelletan 1834: 6). Type. MEXICO. Veracruz, Orizaba, Le Danois s.n. (holotype P00607314).

Type.

Based on Convolvulus purga Wender.

Description.

Perennial twining or trailing herb to 7 m, roots tuberous, stems often dark-red pigmented, glabrous. Leaves petiolate, 4-12 × 3-8 cm, ovate, cordate to sagittate, the auricles rounded or acute, apex narrowly acuminate, mucronulate, both surfaces glabrous; petioles 2.5-6 cm. Flowers solitary or paired from the leaf axils; peduncles 4-8.5 cm long; bracteoles 2 mm long, lanceolate-deltoid; pedicels 10-20 mm, thickened upwards; sepals subequal, glabrous, ovate, acute, obtuse or emarginate and mucronulate, margins scarious, outer 3-8 × 3-4 mm, inner slightly larger, up to 10 × 7 mm; corolla hypocrateriform, 4-6 cm long, widened from the cylindrical base at about half way, glabrous, limb c. 5.5 cm diam., deep pink; stamens and style exserted up to 1 cm. Capsules conical, 7-9 mm long and wide, glabrous; seeds up to 4, 5-6 mm long, puberulent.

Illustration.

McDonald (1987c: 81).

Distribution.

A local Mexican endemic centred on where Hidalgo, Puebla and Veracruz meet. It grows in montane pine and oak forest around 2000 m.

MEXICO. Hidalgo: Trinidad Iron Works, C. G. Pringle 8889 (BM, F, K, MEXU, NY, S, US); Zacualtipan, K.T. Hartweg s.n. (K); H. Puig 3094 (P); Tenango de Doria, O. Alcantara Ayala & E. Ortiz 1183 (MEXU). Puebla: Texiutlán, W. Orcutt 4003 (F); El Mirador, Ocpaco, J.L. Contreras 9105 (MEXU). Veracruz: E.K. Balls 5475 (US); R.V. Ortega 1520 (F).

Notes.

Similar to Ipomoea dumosa with which it is often confused differing in the subequal sepals 6-10 mm long, the apex obtuse or emarginate, the inner sometimes mucronate, and the longer peduncles 4-8.5 cm in length so leaves not enveloping the base of the corolla.

The tuberous roots were much valued in the past as a “safe” purgative. Still sometimes cultivated (McDonald 1994: 100, Don 1838: 271).