Pediomelum mephiticum (S.Watson) Rydb.
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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 - Low perennial herbs, more or less glandular throughout and setose to hirsute with hairs to 2.0 mm, acaulescent or with stems to 3.5 cm, these obscured by stipules, and arising from a deep taproot with an elongated fusiform to cylindrical portion; subtenanean pseudoscapes to 4 cm, these with glabrous to pubescent, stramineous cataphylls to 5 mm. Stipules broadly lanceolate to elliptic, 7-11 x 3-8 mm, sometimes somewhat falcate and laterally emarginate, those at base of plant fused-free, those above becoming free, glabrate to pubescent, quickly stramineous, tardily deciduous to more often persistent. Leaves palmately 5(-6)-foliolate, the 6-foliolate leaves not the earliest, but occurring early in the year; petioles 5.0-12.0 cm, the base of different color and texture and definitely jointed to stem; petiolules 2-3 mm , densely pubescent, blond to purple; leaflets oblanceolate to rarely somewhat orbicular, 2.2-3.5 x 1.6-3.5 cm, the apex broadly the apex broadly acute, rounded or somewhat retuse, cuneate at base, shortly pubescent above, the margins more densely so, more densely pubescent beneath and usually with some longer hairs. Inflorescence globose to elongate, with 4-6(-10) nodes and (2-)3 flowers per node; peduncle 4.7-7.8 cm; rachis 15-25 mm , intemodes to 8 mm; bracts tardily deciduous to persistent, ensiform to oblanceolate, 6-12 X 3-7 mm , elevated on leaf spurs, acuminate to cuspidate at apex, attenuate to cuneate at base, long-pubescent; pedicels 3.5-5.5 mm . Flowers 10-13 mm; calyx moderately setose to hirsute with hairs to 2.0 mm , more densely so on margins of teeth, 10-12 mm long to upper teeth, 10-12.5 mm long to lower tooth, tube 3-4.5 mm , upper teeth hnear, 4-8 x 1-1.5 mm , lower tooth linear-lanceolate to elliptic, 7- 8.5 X 2-3 mm , somewhat longer than other four in bud, becoming ± equal in age, the calyx in fruit gibbose-campanulate, the veins becoming prominent, one to the apex of each tooth and one to each sinus; banner white to ochroleucous, broadly elliptic to somewhat oblanceolate, 9-12 X 6 mm , the claw 2-4 mm , the blade emarginate, biauriculate, the auricles internally callose; wing and keel petals blue to purple; wing petals 11-12 X 2-2.5 mm , the claw 4-4.5 mm , the auricle to 1.5 mm; keel petals 8-8.5 x 2.5 mm, the claw 3.5-4.5 mm; androecium 8.5 mm, anthers roundelliptic, 0.33 mm; gynoecium 8.0 mm, ovary glabrous to pubescent on upper 1/4, base of style concommitantly glabrous or pubescent at base. Fruit body round or obovate in profile, 5-7 x 3.5-5 mm , eglandular, uniformly but sparingly erect-pubescent on upper 1/2, abruptly narrowed to a broadly linear beak 1-4 mm long and at base rarely more than 1.5 mm broad, the beak erect pubescent and about equal to calyx teeth, often contorted and reflexed. Seed reniform, 4.5-5 x 3 mm , reddish-brown to dark brown, or graygreen and black-mottled.
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Discussion
Lectotypus (designated by Ockendon, 1965), G H ! isolectotypi D S (frag)! M O ! N Y (2)! U S ! The type localities given by Watson in Amer. Naturalist and Proc. Amer. Acad. do not agree. Most of Palmer's labels, which may have been written by Watson, if they have any location data, say "Beaver City" or "Southern Utah." The type collection, if indeed from Beaver City, Utah, would be the only known collection of this species from this far north. It is probable that Beaver D a m , Arizona is the real type locale, not Beaver City, Utah. It should be noted that Marcus Jones in his field book (Apr. 4, 1894, as reproduced by Lenz, 1986) stated that "Beaverdam" is also known as "Beaver."
A species localized in the Virgin River Valley, west ofthe Hurricane Cliffs and in the foothills ofthe Pine Valley, Beaver Dam, and Virgin Mountains at approx. 1500 m in Washington County, Utah, and Mohave County, Arizona. R. Traditionally P. mephiticum has been included in the group of species containing P. megalanthum and P. californicum, and was thought to be most closely related to the former, except by Vail (1894), who combined it with californicum. The taxonomy of this group depended in large part on pubescence of the peduncle. Consequently, those specimens herein refened to P. megalanthum var. retrorsum were traditionally included in P. mephiticum. The circumscription I propose is based on floral measurements and admits less variability in both P. mephiticum and P. megalanthum than any traditional prior classification. As here circumscribed, megalanthum contains those plants that have a calyx with tube 6 mm long or longer and lanceolate teeth; mephiticum is applied only to those plants that have a calyx with tube 4.5 mm long or shorter and filiform-linear teeth. Contrary to traditional treatments (except Vail, 1894), mephiticum appears to be more closely related to californicum than to megalanthum.
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Distribution
A species localized in the Virgin River Valley, west ofthe Hurricane Cliffs and in the foothills ofthe Pine Valley, Beaver Dam, and Virgin Mountains at approx. 1500 m in Washington County, Utah, and Mohave County, Arizona.
Utah United States of America North America| Arizona United States of America North America|