Psorothamnus arborescens var. simplifolius (Parish) Barneby

Authors

Rupert C. Barneby

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.

Family

Fabaceae

Scientific Name

Psorothamnus arborescens var. simplifolius (Parish) Barneby

Type

based on Parosela californica var. simplifolia (entire-leaved) Parish, Bot. Gaz. 55: 309. 1913. — "Western part of the Colorado Desert, M. F. Gilman, 51...." — Holotypus, collected in 1904, UC! — Dalea fremontii var. simplifolia (Parish) L. Benson, Amer.

Synonyms

Parosela californica var. simplifolia Parish, Dalea fremontii var. simplifolia (Parish) L.D.Benson, Dalea californica S.Watson, Parosela californica (S.Watson) Vail, Psorodendron californicum (S.Watson) Rydb.

Description

Species Description - Habit nearly of 2 preceding, but canescently silky throughout with subappressed and ascending hairs up to 0.2-0.35 mm long, the lower leaves sometimes green and glabrescent; leaves 3-35 mm long, the leaflets mostly 5 or 7, seldom 3 or 9, oblanceolate to narrowly elliptic, 2-12 mm long, all decurrent on the rachis or some (exceptionally almost all) leaves reduced to a bractlike simple blade less than 1 cm long; racemes 3-15 cm long; calyx densely silky-strigulose externally, 5.2-6.9 mm long, the hypanthium 1.8-2.2 mm deep, the tube 3.2-4.2 mm, the ventral pair of teeth 1.9-3.7 mm long (1.9 mm shorter to 0.5 mm longer than tube) and 1.5-2.1 mm wide; petals indigo-blue; banner 6.3-7.8 mm, its claw 1-1.5 mm, its blade 5.4-6.3 mm long, 5.2-5.8 mm wide; keel 8.5-8.8 mm long, the claws 2.8 mm, the blades 5.8-6.4 mm long, 3.3-3.9 mm wide; pod (6) 7-9 mm long, 4-5 mm diam, the valves subglabrous; 2n = 10 II (Raven, Kyhos & Hill, 1965). — Collections: 29 (v.v.).

Distribution - Rocky benches and bouldery washes, coming out on stony flats with larrea to the edge of the desert floor, 135-1050 m (450-3500 ft), locally plentiful along the s. and s.-e. foothills of San Bernardino Mountains in Riverside and extreme s. San Bernardino counties, California, from Whitewater Pass through upper Coachella Valley to the Little San Bernardino Mountains, n.-e. through Morongo Pass, thence passing into var. minutifolius; from Whitewater extending s.-w. feebly into San Jacinto Valley w. of the desert proper. — Flowering December to May (June).

Discussion

The var. simplifolius, easily recognized in Coachella Valley by its silvery pubescence and leaves mostly pinnate but with decurrent leaflets, might be visualized as combining the foliage of Ps. fremontii with the spotted pod of Ps. arborescens. It has been evaluated repeatedly as an independent species but, as noted under the preceding, forms transitional in their greener, broader leaflets to var. minutifolius are encountered along the zone of floristic transition between the Mohave and Colorado deserts. The resemblance between var. simplifolius (or Dalea californica) and Ps. fremontii has been noted often and has been an obstacle from early times to the separation of D. arborescens and D. fremontii on a sound basis. The keys to the shrubby daleas presented by McMinn (1939, p. 219) and Benson (in Benson & Darrow, 1954, p. 207) assign decurrent leaflets to arborescens and jointed ones to fremontii; but both authors procede to a variety of the latter on the character of decurrent leaflets. Without the character of the pod brought out in this account there could be no logical alternative to reduction of all Xylodalea (or all, perhaps, but Ps. schottii) to one species, composed it is true of several geographic races, but these as confluent as the leaflets themselves.

The quaintly formed epithet simplifolius is descriptive only of the relatively uncommon minor variant in which most, sometimes all leaves are reduced to a small phyllode or a depauperate trefoil. The holotypus of var. simplifolia is an indifferent unicate misleadingly described in the protologue as glabrous throughout. Specimens from Palm Springs, a locality from which there is abundant material for study, demonstrate all gradations between a plant with nothing but phyllodia (L. S. Rose 38,322, CAS, NY, OKLA, UC), with mixed phyllodia and pinnae (Jones in 1925, NY, UC), and with none but normally pinnate leaves. Californian botanists long ago realized that these represent taxonomically insignificant variants of a xerophytic nature, but have not applied the lesson so learned to other races of Psorothamnus. A provocative aspect of the simple-leaved variant is its occurrence in the common range of Ps. arborescens sens. lat. and Ps. schottii, in which simple and trifoliolate leaves, even though their divisions are relatively narrower and always longer, are characteristic. The plastic nature of the leaf in var. simplifolius is of a type that might be expected following introgression between sympatric relatives. The pods of all are so much alike that no corroboration of hybridity can be derived from that quarter.

Distribution

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