Pediomelum argophyllum (Pursh) J.W.Grimes
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Authority
Grimes, J. E. 1990. A revision of the New World species of Psoraleeae (Leguminosae: Papilionoideae). Mem. New York Bot. Gard. 61: 1-114.
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Family
Fabaceae
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Scientific Name
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Description
Species Description - Erect perennial herbs to 1 m tall, one to few stemmed but repeatedly branched above, glandular on upper leaflet surfaces, rarely on stipules, bracts, and calyx teeth, pubescent to strigosesericeous below, young parts and inflorescence densely sericeous; stems arising from the woody, slightly enlarged or subpically enlarged fusiform roots, these commonly with wrinkled, rarely exfoliating epidermis; pseudoscapes lacking, or to 10 cm, sometimes arising laterally from root apex, usually with smooth, not exfoliating epidermis, with or without cataphylls; stems striate to ribbed below, somewhat pithy or fistulose, the base with few crowded cataphylls, the stem below first branches also with few, remote cataphylls, these 9-20 mm, striate, brown and chartaceous at base, sometimes glandular and pubescent at apex. Stipules erect, free, the lowermost commonly tardily deciduous, those above persistent, ensiform to linear, 8-18 x 2-4 mm , green to more commonly marcescent. Leaves palmately 3-6-foliolate, earliest leaves 3-foliolate, leaflet number increasing through the season, then decreasing again to three in late season; petiole 0.2-5.5 cm long, even if as short as 2 mm yet twice as long as petiolules, slightly canaliculate, striate; petiolules 1-4 mm, more densely pubescent than petiole; leaflets narrowly elliptic to oblanceolate or orbicular, 11-45 X 6-22 mm, acute, acuminate to apiculate at apex, attenuate below, glabrous to sparingly sericeous and black-glandular on upper surface, sparingly to densely sericeous and eglandular to sparingly glandular on the lower. Inflorescence with 2-4 nodes, at least one pair of these 10-17 mm distant, very rarely with one node, or with as many as eight, these then uniformly 3-7 mm distant, and the inflorescence oblong, rarely with a single axillary flower at base of peduncle, this 3.0-9.0 cm; rachis 0-6.0 cm; bracts persistent, caudate-elliptic, lanceolate to linear, 3-9 X 1.5-4 mm, sericeous on both surfaces. Flowers subsessile, 7-11 mm; calyx densely or very rarely sparingly sericeous, 4-6 mm long to upper teeth, 6-8 mm long to lower tooth, the tube 2- 3 mm , the upper two calyx teeth linear-lanceolate to lanceolate, 1.5 x 1 mm, the lateral teeth linear- lanceolate to lanceolate, 2 x 1.5 mm , the lower tooth lanceolate, 4.5-5 x 2-2.5 mm, the calyx in fmit becoming broadly and shallowly campanulate and elongating to 12 mm , the lateral sinuses becoming very broad, the lower tooth remaining 2-4 mm longer than the others, any venation obscured by hairs; petals deep blue; banner oblanceolate, obovate or round, 6-7.5 x 3.5-5 mm, the claw 1.5-2 mm, the blade emarginate, biauriculate, the auricles intemally callose; wings 6-7 X 1.5-2.5 mm , the claw 2-2.5 mm, the auricle to 1.5 mm; keel petals 5-6 x 1.5-2 mm, the claw 2-3 mm; androecium 4.5- 5 mm, anthers elliptic, 0.33 mm, apiculate; gynoecium 4-5 mm, ovary canescent on upper %, style canescent at base. Fruit body oblong-oblanceolate in profile, 5-6 x 3-4.5 mm, eglandular, sparingly sericeous on upper V2 to densely canescent overall, the broadly attached beak 3-5 X 2.5 mm , longer than upper four teeth, ± equal to lower tooth. Seed round-reniform, 4-5 X 3-4 mm, dark red-brown, plump, not noticeably compressed.
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Discussion
Holotypus, Pursh, P H ! Lotodes argophyllum (Pursh) Kuntze, Revis. gen. pi. 1: 194. 1891. Psoralidium argophyllum (Pursh) Rydb., N. Amer. Fl.
Psoralea argophylla var. decumbens A. Gray, Expl. surv. railroad route from Mississippi River to Pacific Ocean 12(2): 41. 1860. "Little Muddy River, Aug 10, 1853
Syntypi, G. Suckley with Lts Donelson and Mullen, G H (2)!
Psoralea argophylla robustior J. M, Bates, Amer. Bot. 20:16.1914." 1 Vi miles southwest of Whitman, Grant Co., Nebraska, on the lake border, 2 July 1913, J M. Bates." Holotypus N Y! isotypus G H!
Psoralea collina Rydb., R. Nebr., Rosales 21:54. 1895. "wet meadow. Pleasant Valley, Scotts Bluff Co., Nebraska, July 29, 1891, P. .A. Rydberg 50." Syntypi NEB (2)! and "on hillsides. Fort Robinson, Sioux Country, C E. Bessey 20 July 1887." Syntypus NEB! Psoralidium collinum (Rydb.) Rydb., N. Amer. R. 24: 16. 1919
The type of Psoralea collina Rydberg differs from typical Pediomelum argophyllum by pronouncedly glandular calyx teeth, the lower one only slightly longer than the upper four, and by sparsely canescent calyx. It is the only specimen I have seen with these characters, and came from an area where typical Pediomelum argophyllum is common: I consider it an aberrant form of this species. Rydberg placed P. argophyllum and P. digitatum in Psoralidium, which their habit and the small flowers recall. The calyx and pod are clearly pediomeloid, however. The two species are closely related, united by their mostly eglandular condition, canescent to tomentose fmit, and small flower.
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Distribution
On the Great Plains at approx. 200-1500 m, from southern Manitoba, Saskatchewan, and Alberta south to Missouri and the Texas panhandle, through the eastern foothills of the Rockies to New Mexico. R.
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