Ipomoea megapotamica Choisy in A.P. de Candolle

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

61. Ipomoea megapotamica Choisy in A.P. de Candolle , Prodr. 9: 375. 1845. (Choisy 1845: 375)

Argyreia megapotamica var. puberula Griseb. , Symb. Fl. Argent. 263. 1879. (Grisebach 1879: 263). Type. Based on Ipomoea megapotamica Choisy

Type.

“URUGUAY” (possibly south Brazil fide O’Donell 1948a: 182), Otto s.n. (syntype B, not found, presumably destroyed in 1943), neotype BRAZIL. Mato Grosso do Sul, G. Hatschbach 23711 (NY01013991, designated by Wood et al. (2015: 59), isoneotypes F, MBM?, RB).

Description.

Twining perennial herb reaching 2 m, stems thinly pubescent to subglabrous. Leaves petiolate, 4-10 × 4-10 cm, broadly ovate, cordate, acute and apiculate, minutely scabridulous to thinly appressed pubescent on both surfaces, abaxially paler, often dark gland-dotted, sometimes densely appressed pilose and somewhat velutinous; petioles 2.5-5 cm. Inflorescence of long pedunculate, many-flowered, lax, compound cymes; peduncles 2.5-20 cm, glabrous to puberulent; bracteoles linear, 3-4 mm, caducous; secondary peduncles 1-5.5 cm; tertiary peduncles 1-1.5 cm; quaternary peduncles 0.5-1 cm; pedicels 3-5 mm long, puberulent; sepals subequal 5-7.5 × 3.5-4.5 mm, ovate, acute to shortly apiculate, the apex erect (often slightly bent backwards), tomentellous, often dotted with dark glands, inner elliptic, obtuse to subacute, the margins scarious; corolla 4.5-6 cm long, pale pink with a darker centre, pubescent, funnel-shaped, limb 3-4 cm diam., unlobed. Capsules subglobose, 7 × 6 mm, rostrate with mucro c. 3 mm long, glabrous; seeds 4 × 2 mm, long pilose on margins with hairs to 8 mm.

Illustration.

Figures 8K , 41 .

Variation.

Ipomoea megapotamica is widely distributed in the South American lowlands and quite variable. Specimens from the southern part of its range have leaves abaxially glabrous to thinly pubescent while those from Venezuela and NE Brazil have leaves abaxially softly appressed pilose. These two forms are here recognised as subspecies, which intergrade in central Brazil, for example in Mato Grosso (D. Philcox 3722 (K, NY, RB) from Xavantina and B. Dubs 1840 (ARIZ, S, Z) from the Chapada dos Guimarães).

Figures

Figure 8. Corollas showing variations in form (side view), size, limb lobing and stamen exsertion. A Ipomoea argentea B I. repanda C I. neei D I. electrina E I. habeliana F I. santillanii G I. nationis H I. rubriflora J I. longistaminea K I. megapotamica L I. megalantha M I. neriifolia N I. syringifolia P I. ramosissima Q I. elongata R I. mucronatoproducta. A from Wood et al. 25639 and photo; B from Whitefoord 5244; C from Skutch 2043; D from Breedlove 27626; E from Bentley 203; F from Bourgeau 3024; G from Saunders 987; H from Wood et al. 27678; J from Pastore et al. 2678; K from Wood et al. 28060; L from Hassler 9114; M from Rezende et al. 1011; N from Stutz 1426 and photo; P from Bang 2246; Q from Purpus 3904; R from Wood & Villarroel 25474. Drawn by Rosemary Wise.

Figure 41. Ipomoea megapotamica subsp. megapotamica. A habit B abaxial leaf surface C outer sepal D inner sepal E corolla opened out to show anthers F ovary and style G Young fruit and calyx showing glands at base of sepals. Ipomoea megapotamica subsp. velutina. H leaf J abaxial leaf surface. Drawn by Rosemary Wise A, B from G. Hatschbach 23711; C-G from Fernandez Casas & Molero 4302; H-J from A. Fernandez-R. et al. 9612.