Ipomoea tenuiloba Torr.

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

285. Ipomoea tenuiloba Torr. , Rep. U.S. Mex. Bound. 2(1): 148-149. 1859. (Torrey 1859: 148)

Ipomoea lemmonii A. Gray , Proc. Amer. Acad. Arts 19: 91. 1884 [pub. 1883]. (Gray 1883: 91). Type. UNITED STATES. Arizona, mountains near Fort Huachuca, J.G. Lemmon 2840 (holotype GH00054461, isotypes CAS, P, US).

Ipomoea tenuiloba var. lemmonii (A. Gray) Yatsk. & C.T. Mason , Madroño 31 (2): 106. 1984. (Yatskievych and Mason 1984: 106).

Ipomoea leptosiphon S. Watson , Proc. Amer. Acad. Arts 23: 280. 1888. (Watson 188: 280). Type. MEXICO. Chihuahua, C.G. Pringle 1337 (holotype GH00054514, isotypes E, F, K, NDG, NY, PH, TEX, US).

Type.

UNITED STATES. Texas, near Puerto de Paysano, J. M. Bigelow et al. s.n. (holotype NY00319068, isotype US).

Description.

Perennial herb from a thickened tuberous rootstock (like an elongated bulb), scrambling or twining, completely glabrous. Leaves petiolate, digitate with 5-9 (usually 8) linear, acute leaflets 1-6 × 0.05-0.25(-0.6) cm; petioles 5-35 mm. Flowers axillary, usually solitary, pedunculate; peduncles 1-5 cm, often bent at apex; bracteoles 1-2 mm, filiform, tardily deciduous; pedicels 2-8 mm, thickened upwards, recurving in fruit; sepals unequal, glabrous with scarious margins, broader in fruit, outer 5-9 × 2-3 mm, lanceolate, acute, mucronate, sometimes muricate abaxially, inner 7-14 × 3-4 mm, oblanceolate, rounded, shortly mucronate; corolla 3.5-10 cm long, with a long trumpet-shaped tube gradually widened in upper half to c. 1.5 cm, white, pale pink or purplish, glabrous. midpetaline bands terminating in a mucro, limb c. 2 cm diam.; stamens held at mouth of corolla. Capsules held on a recurved pedicel, compressed-globose, 6-9 mm diam., glabrous, rostrate with mucro up to 5 mm long; seeds 2.5-5 × 2-4 mm, ellipsoid, black.

Distribution.

Semi-desert areas of the United States Southwest and NW Mexico, mostly growing at altitudes of 1700-2200 m, but rather local and infrequently collected.

MEXICO. Chihuahua: S of Guadelupe, E. H. Nelson 4822 (K, US); Temosachi, J. Laferrière 1727 (ARIZ, MEXU); Sierra Canelo, Río Mayo, H.S. Gentry 2529 (ARIZ, F, GH, K, MEXU, US); Colonia Garcia, C.H.T. Townsend & C.M. Barber 271 (BM, F, K, MO, NY, P, US). Durango: Durango-Mazatlan, G. Yatskievych 85-236 (INDIANA, ARIZ); Tepehuanes O. Bravo Bolañsa 150 (MEXU). Sonora: Río Bavispe Region, Sierra de el Tigre, S.S. White 3474 (ARIZ, GH); Yécora, T.R. Van Devender & A.L. Reina-G 2001-844 (MEXU).

UNITED STATES. Arizona: Pima Co, Santa Catalina Mountains, J. Tedford 06-218 (ARIZ); Cochise Co., Mule Pass, F.W. Reichenbacher 811 (ARIZ); ibid., Chiricaha Nat. Mon., D.G. Doramus s.n. (ARIZ); ibid., Coronado Nat. Forest, K. Stieve 49 (ASU). New Mexico: Hidalgo Co, Peloncillo Mts., E. Makings & C.D. Littlefield 3054b (DES, UCR). Texas: type collection.

Note.

This species can be recognised by its distinctive subhypocrateriform corolla, the tube only expanding just below the limb. Yatskievich and Mason (1984) and McDonald (1995) recognised two varieties but these overlap morphologically and geographically. The type has a pale pink or white corolla mostly 5-10 cm long with the inner sepals 11-14 mm in length. Var. lemmonii is more western in its distribution and has a darker, smaller corolla 3.3-5.2 cm long with shorter inner sepals <10 mm long.