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A NEW A OF IPOMOEA (CONVOLVULACEAE) SPECIES FROM OAXACA, MEXICO ANDREW McDonald J. Harvard Unhwsity Herbaria 22 Avenue Divinity MA Cambridge, 02138, U.S. ABSTRACT Recent collecting in Mexico has uncovered a novelty in Ipomoea (Convolvulaccae), gesnerioicles, 7. & from the arid Tehuacan valley of Oaxaca. closely related to bombycina Benth. Hook., It is 7. section Bombycospermmn (Presl) Austin, but differs by producing basally terete stems, mostly - cm - cm terminal inflorescences, and larger, broadly urceolate corollas 3 3-5 long and 1.5 2 broad. RESUMEN Se reconoce una nueva especie del Valle de Tehuacan, Oaxaca, Ipomoea Parece ser gesnerioicles . relacionacla con bombycma, sect. Bomhycosperrnimi^ de la cual se distingue por tallos basales 7. — cm rollizos, inflorescencias usualmente rerminales y corollas nrceoladas, 3 3-5 de largo. Ipomoea McDonald gesnerioides sp. nov. A — cm cm 1.5—2 Ipomoea bombycinae caule basale laeve terete ac coroUis 3 3-5 longis latis statim diagnoscenda. becoming and Vines lignescent, twining. Stems terete, initially erect straight, twining and contorted, the hypocotyl swollen, succulent, smoothish, terete- — cm cm ellipsoid, 5 8 long, to 3 in diam., tan to gray, subdermally chlorophyl- m — many lous, bearing short shoots at the apex, ascending stems 0.5 3 long, mm — new growth growth bark 2 12 in diam., pale green, villous, old tan, - cm membranous, glabrous; internodes 2.5 long; roots fibrous. Leaves petio- .5 1 — cm late; petioles terete, 0.5 3-5 long, reduced on terminal, fertile branchlets, some- pLiberulent, villous or canescent; lamina broadly elliptic or occasionally — — cm cm what rhombic, 2 8 long, 1.5 5 wide, dark green and puberulent above, canescent below, primordially corrugate, margins entire, apex acute or acuminate, base acute or subtruncate, occasionally subcordate on fertile branch- venation pinnate. a scorpioid pseudoraceme comprised of re- lets; Inflmxscence duced, congested, single flowered cymes usually at the apex of fertile branches; mm mm — - peduncles wanting; pedicels terete, 2 9 long, 0.5 in diam., green, 1 mm 5-7 - cm puberulent; sepals subequal, ellipsoid, 1.5 long, wide, coria- 1 1 . ceous, canescent or variably villous, margins entire, apex acute or obtuse; corolla mm mm — 4-8 urceolate, basal portion of tube 6 8 long, in diam., distal portion - cm 1.5-2 cm limb dilating, 2.5 3 long, broad medially, pale green, flaring 173-175. SIDA15(2): 1992 SiDA 1992 174 15(2): FIG. shoots of Ipomoea based on the holotype. A. Flowering branch. B. Fertile ges?7enoic/es 1. Mature Seed. C. fruiting branch. — cm abruptly, 2.5 3 wide, interplicae pale green, the exterior pubescent, plical — cm regions purple, glabrous; stamens subequal, 3.0 3-5 long, white, style sur- mm; passing androecium by 2 stigma bilobate, white. a broadly ellipsoid ca. Fr//// mm 8- - cm capsule, locules 2, valves 4, tan, chartaceous, 1.1 1.3 long, 10 wide, mm mm — — glabrous; seeds 4, ellipsoid, 3 —angled, 6 7 long, 3 3.5 wide, dark brown, minutely puberulent with dense lanate tufts of hair along angle margins cm toward hilum, hairs white, to long. 1 W Hwy MEXICO. Type: Oaxaov: 10.4 mi of Santiago Astata on 200, in scrub-deciduous MEXU!, forest, 9 Mar 1985, Luckaw 2605 (holotyfk: TEX!; isotyphs: USl). & Ipomoea gesnerioides most closely approaches hombycina Benth. Hook., type /. species oilpornoea sect. Bomhycospmnum (Presl) D. Austin, by the presentation of McDonald, Ipomoea 175 - cm stem growth becomes a swollen hypocotyl 3 wide, initially erect that later 1 somewhat twining, corrugate leaves, scorpioid pseudoracemes, urceolate corol- among las, and densely lanate seeds. Ipomoea gesnerioides is unique all other Ipomoea ofMexico, however, producing mostly terminal, scorpioid pseudoracemes and in - cm 1.5-2 cm with large (3 3.5 long, medially in diameter) urceolate corollas a pale green and purple limb. Flowers of/, bombycina are generally born on axillary cm pseudoracemes (sometimes terminal), and corollas never exceed 2.5 in length cm The two and in diameter. vegetative features of these species are also 1 distinctive, bombycina bearing a rough, furrowed, swollen hypocotyl, while the /. swollen hypocotyl of/, gesnerioides terete and relatively smooth. Both species are is restricted to the tropical deciduous forest of southern Mexico, bombycina /. occurring from Jalisco to Guerrero in tropical deciduous forest, and gesnerioides /. from type locality in the arid Tehuacan Valley of Oaxaca. its