Pediomelum rhombifolium (Torr. & A.Gray) Rydb.

  • Authority

    Grimes, J. E. 1990. A revision of the New World species of Psoraleeae (Leguminosae: Papilionoideae). Mem. New York Bot. Gard. 61: 1-114.

  • Family

    Fabaceae

  • Scientific Name

    Pediomelum rhombifolium (Torr. & A.Gray) Rydb.

  • Description

    Species Description - Decumbent perennial herbs with stems to 1 m, pubescent with short erect-appressed hairs, rarely hirsutulose, at most minutely glandular on upper leaflet surfaces, occasionally on stipules, rarely on bracts; roots fibrous and much-branched, or often forming a caudex of swollen, fusiform root-branches, remote tubers commonly forming, these usually arising some distance from the soil surface and 1.5-4 x 0.5-1.5 cm; pseudoscapes lacking or to 10 cm; cataphylls brown and obviously veined, 7-13 mm; stems few to numerous from the apex ofthe pseudoscapes, only rarely branched, striate, eglandular and pubescent with short incurved curly hairs, at base with crowded remains of cataphylls and stipules. Stipules lanceolate, 3-6.5 x 1-2 mm, free, or lower ones sometimes adnate only to a phyllode, the upper free, all glabrate except on margins, mostly becoming reflexed, persistent. Leaves pinnately trifoliolate, the early ones usually with much smaller leaflets, or reduced to a phyllode; petioles 0.9-9.0 cm, distinctly ribbed and pubescent with short erect-ascending hairs, the base of same color and texture as petiole or swollen and rarely also somewhat winged, not jointed to stem; rachis 3-17 mm; petiolules 1-1.5 mm, blond and pubescent; leaflets lanceolate, rhombic or orbicular, the lateral leaflets asymmetrically so, 0.9-4.7 X 0.6-2.8 cm, truncate-attenuate at base, broadly acute to rounded at apex, upper surface glabrous to uniformly pubescent, and glandular with faint to dark brown glands, lower surface glabrate or pubescent mostly along veins and faintly glandular. Inflorescence globose or ovoid, with 1-6 nodes and three flowers per node, not elongating appreciably in frut; peduncle 0.8-8.5 cm, narrowed and glabrate at base; rachis 0.3-1.0 cm. internodes 3-5 mm; bracts persistent, spatulate, ligulate to lanceolate, 1-3 x 0.5-1 mm , lower ones usually somewhat smaller than those in middle, somewhat lacerate, dorsally glabrate except on margins; pedicels 1-2 mm . Flowers 7.5- 11 m m; calyx strigose, eglandular, 4.5-6 mm long to upper teeth, 4.5-6.5 mm long to lower tooth, the tube 2.5-3.5 mm , all teeth lanceolate, the upper four 1.5-2.0 mm, the lower one 2.5-3.0 mm, all 1-1.5 mm broad at base, internally minutely pubescent, in fruit the veins to teeth and to sinuses adjacent to lower tooth becoming prominent; petals brick-red, salmon-pink, or rarely white; banner oblanceolate or rhombic, 7.5-10 X 4-5 mm , the claw 2.5 mm , the blade emarginate, biauriculate, the auricles internally callose; wings 7-10 x 2-2.5 mm , the claw 2.5- 3 mm , the auricle 0.5-1 mm; keel petals 5-7.5 X 2-2.5 mm , the claw 2.5-3 mm; androecium 6-7 mm , anthers elliptic, to 0.5 mm; gynoecium 5-6.5 mm , short-pubescent on apex, style pubescent at base or on lower Vi. Fruit body round in profile, 4.5-5 x 3-4 mm, eglandular, pubescent on upper Vs, rather abruptly contracted to a beak 6-8 mm long and at base 1.5 mm broad, uniformly pubescent, surpassing calyx teeth. Seed lenticular, bulging in middle, 4 x 3-3.5 mm, gray-green, commonly black-mottled.

    Distribution - A species of sand, sandy-loam or detritus, in open places in woodlands and grasslands, on sand dunes along lakes, rivers or ocean, and adventive in disturbed places from 0-2250 m. From Cameron Parish, Louisiana and Marshall County, Oklahoma, through eastern and southern Texas, across northem Mexico from Baja Califomia to Tamaulipas, and south in the mountains to northem Veracruz and north-central Oaxaca. R.

  • Discussion

    Holotypus N Y ! isotypi BM ! GH ! GO ET ! K! US (frag)! Lotodes rhombifolium (Ton. & A. Gray) Kuntze, Revis. gen. pi. 1: 194. 1891.

    Pediomelum brachypus Rydb., N. Amer. R. 24: 24. 1919. "MEXICO, Oaxaca, Los Naranjos, Aug 1908 C. A. Purpus 3049" Holotypus NY! isotypi GH! MO! US! Psoralea brachypus {Rydb.) Standley, Publ. Field Mus. Nat. Hist., Bot. Ser. 11: 161. 1936.

    Pediomelum sonorae Rydb., N. Amer. R. 24:24. 1919. "MEXICO, Sonora, vicinity of Alamos, 17 Mar 1910, /. A^. Rose, P. S. Standley & P G. Russell 13025" Holotypus N Y! isotypus US!

    Psoralea decipiens M. E. Jones, Imprints from Contr. W. Bot. 18: 41. 1933. "MEXICO, Jalisco, Guadalajara, La Barranca, 23 Nov 1930." Holotypus, M. E. Jones 27178, P O M ! isotypus G H!

    Pediomelum coryi Tharp & F. Barkley, Madrono 8: 54. 1945. "Texas, Katherine, 22 Mar 1907, W. L. Bray & H. H. York 5." Holotypus TEX! isotypi G H ! NY!

    Pediomelum rhombifolium is extremely variable as regards pubescence, leaflet shape and size, in petiole and peduncle length, and the ratio ofthe two. However, this variation is only discrete at the populational level, and the various character states are mixed and matched independently throughout the range. Greenhouse and field observations show that P. rhombifolium is autogamous, the ovary being fertilized before the corolla has fully expanded. Nonetheless, the flowers produce large quantities of nectar. The extreme variability between populations and the low variability within them is not surprising in an autogamous species. A few individuals from very localized populations in northem Texas and southern Oklahoma are unusual in that they have round seeds with the white ridge incompletely developed. Since these specimens are all rare and are found in populations with normal individuals, they are considered aberrant.

  • Distribution

    Louisiana United States of America North America| Oklahoma United States of America North America| Texas United States of America North America| México Mexico North America| Baja California Mexico North America|