Ipomoea thurberi A. Gray

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

254. Ipomoea thurberi A. Gray , Syn. Fl. N. Amer. 2: 212. 1878. (Gray 1878: 212)

Ipomoea gentryi Standl., Publ. Field Mus. Nat. Hist. , Bot. Ser. 22: 46. 1940. (Standley 1940b: 46). Type. MEXICO. Chihuahua, Río Mayo, H.S. Gentry 2497 (holotype F0054842, isotypes ARIZ, MO).

Ipomoea sessilis L.O. Williams, Fieldiana , Bot. 32 (12): 195. 1970. (Williams 1970a: 195). Type. GUATEMALA. Huehuetenango, J. Steyermark 51566 (holotype F0054897).

Type.

UNITED STATES. Arizona, G. Thurber 966 (holotype GH00054547).

Description.

Twining or trailing perennial from a thickened woody tuberous rootstock like a xylopodium; stems glabrous. Leaves petiolate; at least sometimes held at right angles to petiole, 1-5 × 2.5-6 cm, deltoid, finely acuminate and mucronate, margin undulate, base sagittate with basal auricles acute, sometimes bifurcate and leaves becoming ± 5-lobed, thinly pilose on both surfaces; petioles 0.6-2.4 cm. Inflorescence of solitary, axillary flowers; peduncles 3-5 (-7) mm, sometimes muricate or with a few stipitate glands; bracteoles 1-2 mm, deltoid; pedicels 4-12 mm, thicker than peduncle and widened upwards; sepals equal, glabrous, 14-25 × 3-4 mm, narrowly lanceolate, acute to acuminate, mucronate, outer sometimes verrucose near base; corolla 5-9 cm long, flared, funnel-shaped, very gradually widened from a narrow basal tube, pale pink, glabrous, limb 5-6 cm diam.; ovary 3-locular. Capsules subglobose to ovoid, 6-7 mm, strongly rostrate with mucro 4-6 mm long, glabrous; seeds up to 6, c. 4 mm long, ovoid, dark brown, tomentellous.

Distribution.

A species with a strikingly disjunct distribution between Central America and the Sonora desert region that is very unusual and merits investigation. It is mostly found between 1100 and 1900 m in dry rocky areas in open oak woodland.

NICARAGUA. Hac. Corpus, Chontales, W.D. Stevens 22449 (MO).

GUATEMALA. Type of Ipomoea sessilis .

MEXICO. Chihuahua: H.S. Gentry 2612 (F, K); Nabogame, J.E. Leferrière 1612 (ARIZ, ASU, MEXU). Durango: Buenos Aires, Tepehuanes, P. Tenorio & S. Romero 1193 (MEXU). Est. México & Dist. Fed.: Temascaltepec, Chorrera, G.B. Hinton 4746 (K); ibid., G.B. Hinton 6502 (K). Nayarit: G. Flores-Franco et al. 2751 (MEXU). San Luis Potosí: C.C. Parry & E. Palmer 665 (P). Sonora: between Ures and Moctezuma, N. Snow & T.P. Prinzie 6594 (MO); Los Pilares, 23 km E de Yécora, T. Van Devender et al. 98-911 (ARIZ, ASU); Yécora, A.L. Reina-G et al. 97-717 (MEXU).

UNITED STATES. Arizona: Huachuca Mts, J.G. Lemmon 2833 (BM, GH, K, P); Cochise Co., Canelo Hills, G. Yatskievich 80-347 (MO); Santa Cruz Co., Pena Blanca Lake-Sycamore Canyon, D.F & S. Austin 7603 (ARIZ, ASU).

Note.

Very characteristic are the solitary, very shortly pedunculate flowers, the gradually widened flared corolla and the long, narrow sepals.

• Species 255-257 (and more distantly 258) form a small clade of closely related species.