Psorothamnus arborescens var. minutifolius (Parish) Barneby
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1977. Daleae Imagines, an illustrated revision of Errazurizia Philippi, Psorothamnus Rydberg, Marine Liebmann, and Dalea Lucanus emen. Barneby, including all species of Leguminosae tribe Amorpheae Borissova ever referred to Dalea. Mem. New York Bot. Gard. 27: 1-892.
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Family
Fabaceae
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Scientific Name
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Type
based on Parosela johnsoni var. minutifolia (tiny-leaved) Parish, Bot. Gaz. 55: 308. 1913.— "Mouth Panamint Canon [Inyo Co., Cal.] May 11, 1906, Hall and Chandler 7002; Providence Mountains [San Bernardino Co.] May 24, 1905, Brandegee." — Lectotypus, Hall
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Synonyms
Parosela johnsonii var. minutifolia Parish, Dalea fremontii var. minutifolia (Parish) L.D.Benson, Parosela wheeleri Vail, Psorodendron wheeleri (Vail) Rydb., Dalea arborescens var. wheeleri (Vail) Tidestr., Parosela fremontii var. wheeleri (Vail) C.B.Rob. ex J.F.Macbr.
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Description
Species Description - Habitally like var. arborescens, but more commonly glabrescent or glabrate, nevertheless sometimes densely gray-villosulous; old branches ashen or stramineous, usually much contorted and ligneous; hairs on leaf and calyx up to (0.2) 0.3-0.5 mm long, the foliage varying from bright yellowish-green to canescent; leaves up to 3.5 (5.5) cm long, the leaflets lanceolate to rhombic-ovate or -elliptic, obtuse or subacute, 3-13 (17) mm long; flower a little smaller than that of var. arborescens, the calyx as given in key; petals either indigo blue or violet, the banner 7.6-9 mm, its claw 1.8-2.2 mm, its blade 6.4-7.2 mm long, 4-7.4 mm wide; keel 8.4-10.3 mm long, its blades 6.3-8.2 mm long, 3.5-4.8 mm wide; pod as in var. arborescens, but the valves apparently always glabrous; n = 20 II (Raven, Kyhos & Hill, 1965, sub D. fremontii minutifolia); 2n = 10n (Raven et al., 1965, sub D. fremontii fremontii). — Collections: 54 (v.v.).
Distribution - Rocky and sandy desert hillsides, canyon-benches, sometimes on talus under cliffs, 150-1890 m (500- 6300 ft), locally common through w.-centr. and n. Mohave Desert, California, from n.-e. Kern County (Rand and El Paso mountains) n. to s. Mono County (lower Owens Valley and near Benton), e. to w.-centr. San Bernardino County (Ord and Calico mountains, where overlapping and confluent with var. arborescens) and in Inyo County to Death Valley, thence extending across the Last Chance and Funeral ranges into the s. point of Esmeralda and extreme s. Nye County, Nevada. - Flowering April to June.
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Discussion
As here circumscribed, var. minutifolius differs from var. arborescens in no respect other than the smaller flower and even in these terms cannot be separated by any known discontinuity. It is a somewhat artificial segregate, although from the biological point of view it is the local, large-flowered var. arborescens which seems to be the derived form. On the Mohave Desert in the Barstow region populations of var. minutifolius and var. arborescens exist very nearly in contact with each other, the former apparently in more rocky sites in the foothill canyons (Ord and Calico mountains), the latter out on the open desert. In western, central and northern Mohave Desert, Owens Valley, and the Death Valley region, where it becomes especially abundant, var. minutifolius is the only member of sect. Xylodalea recorded. It varies like var. arborescens in pubescence, and considerably more so in amplitude of the leaflets, but a densely villosulous phase comparable to the typus of Ps. arborescens is rare.
The substance of var. minutifolius has been treated in the literature under a variety of synonyms but has always been separated (except for the villous phase of it) from Ps. arborescens at the specific level. Most students of the group have subordinated it to Ps. fremontii, sometimes recognizing different leaf- and pubescence-forms as coordinate varieties, although these have never been correlated with respectable geographic patterns of dispersal. It is construed in these pages as specifically distinct from Ps. fremontii without any attempt to deny the manifestly close relationship between them. Whatever the status of the two taxa may be, they are allopatric and sharply characterized by the pods. Genuine Ps. fremontii occurs in California only on the sedimentary ranges of far eastern Mohave Desert, whereas var. minutifolius has been reported only from granitic and volcanic bedrock. A relatively small area lying to east of the San Bernardino Mountains equidistant more or less between var. minutifolius and var. arborescens to the north, var. simplifolius to the west, and Ps. fremontii to the east, is occupied by populations of Psorothamnus that are transitional between the first two mentioned, and sometimes mimic Ps. fremontii in their silvery-strigulose vesture. These are referred to Ps. arborescens sens. lat. because of the gland-dotted pods but can only be assigned arbitrarily to either var. minutifolius or var. simplifolius (Cottonwood and Sheephole ranges: Jepson 5982, UC-JEPS; Hall 6024, 6057, UC; Ferris & Bacigalupi 8129, UC).
It should be noted that the epithet minutifolius has been transferred in the literature from the Psorothamnus common in the canyons of the Panamint Mountains to the form of Ps. fremontii with linear leaflets described below as var. attenuatus.
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Distribution
United States of America North America| California United States of America North America| Nevada United States of America North America|