Rhynchosia latifolia Nutt. ex Torr. & A.Gray
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Authority
Grear, John W. 1978. A revision of the New World species of Rhynchosia (Leguminosae-Faboideae). Mem. New York Bot. Gard. 31 (1): 1-168.
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Family
Fabaceae
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Scientific Name
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Description
Species Description - Herbaceous vine from woody rootstock, to 1.5 m, the stems trailing or twining (rarely suberect), one to several, few-branched, angular, softly hirsute (especially along angles), the hairs tawny. Stipules subulate-lanceolate, acuminate, caducous, 2.5-7.5 mm long, 2-2.5 mm wide. Petioles hirsute, (2.5-)3-5(-6) cm. Leaflets 3, broadly ovate to ovate-rhombic or orbicular (the lowermost sometimes unifoliolate and reniform), coriaceous, obtuse, acute or abruptly acuminate, often mucronate, base obtuse to subcordate, (2-)3-7(-8) cm long, (l-)2-6(-7) cm wide, finely and loosely strigose above, villous and gland-dotted beneath, terminal petiolule 1-2 cm, the laterals subobsolete to 4 mm, stipels lacking. Inflorescences multiflorate, equalling or exceeding the leaves, non-branching, 3-20 cm, the flowers lax and scattered along raceme, peduncle subobsolete to 4 cm, pedicels 1-3 mm. Bracts subulate to lanceolate, long-acuminate, caducous, 4-6 mm long, 0.5-1 mm wide. Calyx usually exceeding the corolla, hirsute, 8-15 mm, tube 2-3 mm, lobes lanceolate, acuminate, 7-10 mm, vexillar sinus 4 mm. Corolla mustard yellow, 8.5-13 mm. Standard obovate, emarginate, minutely gland-dotted and hirsutulous, 9.5-14 mm long, 6-7 mm wide, auricles 0.5 mm, claw 1 mm. Wings oblong, glabrous, 8.5-13 mm long, 2-2.5 mm wide, claw 2 mm. Keel blades falcate, glabrous, 8.5-13 mm long, 3-4 mm wide, claw 2-3 mm. Stamens 8-12 mm. Fruits ovate-oblong, compressed, villous and puberulous intermixed, 1.5-2 cm long, 7-9 mm wide, beak 1-2 mm. Seeds suborbicular, compressed, brown, grey or mottled, 3-4 mm long, 3-4 mm wide, hilum ovate, 1 mm, strophiole lobes cuneate.
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Discussion
Phaseolus latifolius (Nuttall ex Torrey & Gray) Eaton & Wright, N. Am. Bot. 353. 1840. Dolicholus latifolius (Nuttall ex Torrey & Gray) Vail, Bull. Torrey Club 26: 114. 1899. Rhynchosia latifolia ß Torrey & Gray, Fl. N. Am. 1: 285. 1838. Type: TEXAS. Sand Hill. Dr. Leavenworth sn, w/o date (holotype, NY!). Rhynchosia torreyi Vail, Bull. Torrey Club 22: 459. 1895. Dolicholus torreyi (Vail) Vail, Bull. Torrey Club 26: 113. 1899. Type. ARKANSAS. Nuttall sn, w/o date (holotype, BM!; phototype, M0!; isotypes, K!, NY!; paratype, Dr. Hale sn, NY!). Local Names. Peavine (Texas: Robertson Co.); prairie Rhynchosia (Arkansas: Pike Co.; Texas: Grayson Co.). Rhynchosia latifolia, as it occurs throughout most of its range, is a remarkably uniform plant with prostrate or weakly twining stems and elongate racemes exceeding the leaves. However, an erect, apparently depauperate form, with shorter racemes and somewhat smaller leaflets has been collected a few times. Torrey & Gray (1838) distinguished this as a variety and Vail (1895) elevated it to specific rank as R. torreyi. Turner (1959) considers it to be an intermediate between R. latifolia and R. difformis where the two occur together in Texas. I do not favor the hybrid explanation for the following reasons: (1) habit and leaflet morphology are variable in many species of the genus; (2) the short racemes are probably immature ones which have not fully elongated; (3) R. difformis does not have erect or suberect stems; and (4) only a very few collections exist, and are of sporadic occurrence, some being from Missouri, outside the range of R. difformis. Rhynchosia latifolia resembles R. reticulata as to pubescence and habit but it is not as variable as to leaflet shape and also lacks stipels.
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Distribution
Distribution. Southern Missouri south to Louisiana, east to Mississippi and west to eastern Texas and Oklahoma (Fig. 29). Occurring in sandy or gravely soils of pine and oak woodlands, in sandy prairies, limestone glades, high rocky open woods, along streams and in thickets; at elevations below 800 m.
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