133. Ipomoea hartwegii Benth., Pl. Hartweg. 15. 1839. (Bentham 1839-57: 15)

Ipomoea albidiflora Matuda, Cact. Suc. Mex 18 (3): 78. 1973. (Matuda 1973: 78). Type. MEXICO. Michoacán, R. Hernández Magaña 700 (holotype MEXU00204487, isotype MEXU).

Type.

MEXICO. K.T. Hartweg 96 (holotype K000612756, isotypes BM, E, GH, K, NY, OXF).

Description.

Twining perennial herb to c. 2 m, stems woody below, white-pubescent; root tuberous, resembling a small turnip. Leaves petiolate, small, 2-4.5 × 1.8-3.5, ovate-deltoid, pubescent, glabrescent; petioles 0.6-4.3 cm, pubescent. Inflorescence of solitary flowers (rarely in cymes with up to 3 flowers); peduncles 2.5-16 cm, glabrous or pubescent; bracteoles early caducous, not seen; secondary peduncles (if present) 1-3 cm; pedicels 10-30 mm, glabrous; sepals slightly to very unequal, scarious-margined, outer 6-8 × 2. 5-3 mm, oblong to narrowly elliptic, obtuse, abaxially hispid with bulbous-based hairs (rarely glabrous), inner 7-9 × 3-4 mm, oblong-obovate, obtuse, rounded or retuse, with broader scarious margins, glabrous; corolla 4.5-8 cm long, funnel-shaped, white with lavender flush, (sometimes pink), glabrous, limb 4-7 cm diam. Capsules 7-12 × 6-9 mm, ovoid, glabrous; seeds black, 7-8 mm long, shortly pubescent on the angles.

Illustration.

Figures 3D, 78.

Distribution.

Endemic to central Mexico, where it grows in scrub and rough grassland at around 2000-2100 m.

MEXICO. Chihuahua: Río Mayo, Guasaremos, H.S. Gentry 1558 (ARIZ), ibid., 2333 (ARIZ, MO). Est. México & Dist. Fed.: Temascaltepec, Cerro Muñeca, G.B. Hinton 1382 (BM, K, MO), ibid., Ipericones, G.B. Hinton 8083 (K, P, S). Guanajuato: M. Doblado, E. Carranza & E. Pérez 4938 (IEB, MEXU); La Presa del Chupadero, E. Ventura & E. López 9550 (IEB, MEXU); Coroneo, E. Carranza 5087 (IEB, MEXU). Guerrero: just N. of Arteaga, D.F. Austin & F. de la Puente 7691 (FTG). Jalisco: 5 miles E of Zapotlanejo, D. Tuttle 279 (ARIZ); Tepatitlán-Pegueros, R. Guzmán et al. 950 (MEXU). Michoacán: Mun. Morelia, J. Santos Martínez 2228 (IEB, MEXU, MICH); San Bernardo E. Carranza 5546 (IEB, MEXU). Morelos: Cuernavaca, C.G. Pringle 13779 (ARIZ, S). Nayarit: Santa María del Oro, H.S. Gentry 11012 (ARIZ); Tepic, R. Kral 27530 (MO). Querétaro: San Juan del Rio, C.G. Pringle 10028 (BM, K, MEXU, MO, S); Humilpan-El Pueblito, E. Argüelles 3220 (MEXU). San Luís de Potosí: Guadalcázar, R. Torres Colin 15218 (MEXU). Sinaloa: Villa Unión, R.L. Oliver et al. 727 (MO). Zacatecas: Coulter 1022 (K).

Notes.

Ipomoea hartwegii is a poorly understood species. It is characterised by the long-pedunculate 1-2-flowered inflorescence and the sepals with conspicuous scarious margins. The leaves are shortly petiolate, especially in contrast to the long-pedunculate flowers and the sepals are usually abaxially hispid with bulbous-based hairs, although in some specimens they are glabrous. It is not unlike a solitary-flowered small-leaved form of Ipomoea orizabensis .

Ipomoea hartwegii is quite frequently confused with I. proxima (as I. dimorphophylla) but that species has a shortly pedunculate cymose inflorescence and the leaves are often lobed or at least with undulate margins.

• Species 134-141 are all Mexican species with white flowers and similar morphology although phylogenetic relationships between species have not been determined. Most but not all have hirsute sepals