Dalea mollis Benth.
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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
"In vicinibus Monterey legit Coulter." — Holotypus, collected probably in or near the Yuma Desert, in extreme s.-e. California or adjoining Arizona, in 1832, K (herb. Benth.)! isotypus (Coulter 430), GH!- Parosela mollis (Benth.) A. Heller, Cat. N. Amer.
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Synonyms
Parosela mollis (Benth.) A.Heller, Parosela pilosa Rydb., Dalea mollis subsp. pilosa (Rydb.) Wiggins
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Description
Species Description - Annuals, germinating either in fall or winter, often flowering precociously when only 3-10 cm tall, but when the season permits with an ultimately lignescent, orange root and numerous, radiating, prostrate or distally incurved, simple or branched, stramineous but prominently gland-tuberculate stems up to 1-3.5 (6.5) dm long, pilose-pilosulous throughout or nearly so with fine, divergent or loosely ascending hairs up to (0.4) 0.5-1.1 (1.3) mm long, the foliage glaucescent, the leaflets equally pubescent on both sides or glabrate above, grossly livid-pustulate beneath, the vesture of the silky-barbate inflorescence commonly tarnishing when dry, that of the leavesusually unchanged; leaf-spurs 0.5-1.5 mm long\ stipules subulate, lanceolate, or lance-caudate, (0.6) 1-2.5 mm long, thinly herbaceous becoming stramineous, pubescent dorsally and charged with one or more large glands; intrapetiolular glands 0; post-petiolar glands large, orange or livid, prominent, and often ± scattered and not directly opposed to the petiolule; leaves (0.5) 1-3.5 cm long, slenderly petioled, with (3) 4-6 (7) pairs of obovate, obcordate, cuneate-obcordate, suborbicular, or oblong-obovate, deeply notched to subemarginate, loosely folded leaflets (2) 3-8 cm long, their margins plane, neither toothed nor undulate; peduncles mostly leaf-opposed, in some dwarf plants terminal and solitary, 0.2-2.5 (4.5) cm long; racemes densely many-flowered, ovate in outline early becoming oblong or narrowly cylindric, 8-14 mm diam, the flowers spreading in early anthesis, then declined and loosely retrorse-imbricate in fruit, the pilosulous axis (0.5) 1-3.5 cm long; bracts lance- or elliptic-acuminate or -caudate, (3) 4.5-8 mm long, thinly herbaceous, green or purplish, glandular and pilose dorsally, glabrous within, gland-tipped; pedicels 0.3-0.6 mm long, the black or livid, prickle-shaped glands at base and toward apex (0.3) 0.4-1 mm long; calyx 3.3-6.6 mm long, silky-barbate with ascending, straight, spiral hairs up to 1-1.8 mm long, the tube 1.6-2.5 mm long, the orifice symmetric, the ribs subfiliform, commonly castaneous, the hyaline intervals charged with one row of (1) 2-6 small orange glands, the teeth deltate- or triangular-aristate, of about equal length, (2.5) 2.7-4 mm long, nearly always gland-spurred; petals whitish, but the keel-tip and sometimes the blade of the banner tinged with lilac or dull crimson, the banner gland-sprinkled in the hyaline eye, the wing- and keel-blades charged with a few glands at base, the wings gland-tipped, the inner petals raised ± 0.9-1.4 mm above the hypanthium rim; banner 3-4.2 mm long, the claw 1.2-2.1 mm, the deltate-, ovate- or sub-orbicular-cordate, subacute to emarginate blade (1.5) 1.7-2.9 mm long, 2.2-3.2 mm wide; wings 2.9-4.3 mm long, the claw 0.9-1.4 mm, the ovate-oblong blade obliquely notched at apex, 2.1-3 mm long, 1.1-1.4 mm wide; keel 3.4-4.5 mm long, the claws 1-1.6 mm long, the half-obovate blades 2.3-3.4 mm long, 1.4-2 mm wide; androecium 10-merous, 3.5-5.7 mm long, the longest filament free for 1.2-2 mm, the gland-tipped anthers 0.4-0.6 mm long; pod obliquely obovoid, 2.2-2.7 mm long, the style terminal but excentric, the submembranous valves transparent in the lower 2/3, distally opaque, minutely gland-sprinkled and pilosulous, the keels filiform; seed pale-brown, lustrous, ± 1.8-2.2 mm long; 2n = 16 (Mosquin); n = 8 (Spellenberg, 1973).— Collections: 106 (v).
Distribution and Ecology - Sandy and gravelly washes, bajadas, sometimes on dunes, mostly below 700 m (2300 ft), around Salton Sea descending to —50 m, reportedly reaching 1200 m in Sierra Borja in Baja California, widespread and common over the floor of the Sonoran Desert from s.-e. Mohave Desert in San Bernardino County and Coachella Valley, Riverside County, California, to the valley of the Colorado and lower Gila rivers in s.-w. Arizona, s. in Sonora to the latitude of Guaymas, and through the islands of the Gulf of California and the deserts of Baja California to the Llanos de Magdalena and Bahia de La Paz, lat. 24° 12' N., reaching the Pacific coast at Isla Cedros and at Isla Sta. Margarita on Bahia Magdalena. — Flowering January to May.
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Discussion
(Plate XXXIII)
Except in a small area lying between the Colorado River delta and Sierra Juarez, D. mollis is the only species of its type found on the true deserts of Sonora, Baja California, and the islands in the Gulf of California. From the delta north through the Colorado Desert and the lower Colorado valley in Arizona it is sympatric and sometimes directly associated with the related and similar D. mollissima. Both species vary greatly in stature, often starting precociously into flower when only a few centimeters tall, yet capable, if the rains come with appropriate timing and volume, of forming leafy mats, up to 5-8 (rarely 13) dm in diameter, of radiating, branched stems which bear an indefinite succession of leaf- opposed racemes until growth is halted by heat of summer. The orange root, at first filiform or nearly so, can attain a girth of a centimeter or more, but although eventually tough and woody rarely or never persists into a second year. The glaucous, finely pilose leaves, dotted beneath like the stramineous stems with prominent livid glands, and the dense spikes of nodding, silky-barbate calyces, distinguish D. mollis and D. mollissima collectively from all species except D. neo-mexicana, the differential characters of which have been stressed above.
Rydberg (1919, p. 50, in clave) and Wiggins (1940, p. 51-52, PL X, XI) have brought out the main differences between D. mollis and D. mollissima, characters repeated, with some change of emphasis, in the foregoing sectional key. In general D. mollis is the more slender of the pair, but its spike varies in thickness with the varying length of the calyx- teeth, and at its largest mimics the always thick-spiked D. mollissima; but even here the tube of the calyx remains absolutely shorter, and the androecium is longer relative to the calyx-teeth. The vesture of the foliage in D. mollis tends to remain silvery in the herbarium, although that of the spike tarnishes quickly after drying; in D. mollissima the hairs of leaf and calyx alike turn golden or yellowish after a few months in the herbarium. In their common range the two species, despite the extraordinary similarity in gross aspect, remain sharply characterized, and I have seen no specimen of ambiguous identity. Occasionally one character, such as the gland recessed into the notch of the wing, may fail (A. Hess 35, NY), but such individuals do not bridge the discontinuity. Where the two species occur together they occupy the same habitat. Probably the small, dull-hued flowers are autogamous, which would permit two closely related species to mingle without losing their identity. For rapid identification, the plane margins of the leaflets and the narrow bracts are the best and most easily observed diagnostic features of D. mollis.
No clear racial division is apparent in D. mollis. Wiggins (1940, p. 46, in clave) attempted to distinguish small-flowered, typical D. mollis, with calyx 3-4 mm long, from a subspecies pilosa with calyx at least 6 mm long. In my view the material presents an uninterrupted series, the calyx measuring from 3.3 to 6.6 mm disregarding pubescence and glands terminal to the teeth. Within a colony the flower is ordinarily very uniform in size, as might be expected of self-fertile species; nevertheless occasional plants are found growing in what appears to be an otherwise uniform population which would be referred, by Wiggins’ criteria, to both subspecies (Ripley & Barneby 4264, NY). The petals vary much less than the calyx, the keel becoming more exserted as the teeth become shorter. An extremely short-toothed calyx is comparatively rare, known from scattered stations and groups of stations chiefly in and near the Salton depression (Yuma Desert; Borrego Valley; Coachella Valley), but has been found in Mohave County, Arizona (near Yucca), and as far south in Sonora as Guaymas. Large-flowered D. mollis, prevalent over Baja California (as suggested by Wiggins’s map, 1940) has been collected as far north as Ehrenberg on the Colorado River, and at Thousand Palms near the species’ northern limit in California.
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Objects
Representative: UNITED STATES. California: Jepson 15,479 (JEPS); Eastwood 3058 (CAS, NY); E. K. Balls 12,961 (DAO, POM). Arizona: Jones 4431 (NY, POM): A & R. Nelson 11,135a (NY, UC). MEXICO. Sonora: Shreve 5827, 5842 (ARIZ, US): Ripley 14,316 (ARIZ, CAS, NY); Mason, Turner & Hastings 1836 (ARIZ, MEXU). Baja California (Norte): Johnston 4235 (F, NY, UC); Wiggins 5359 (NY, UC); Palmer 512 (NY); Moran 8065 (SD). Baja California (Sur); Gentry 7362, 7460, 7538 (ARIZ, UC); Wiggins 5457 (NY, UC), 7937 (F, UC); Carter 2745 (UC).
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Distribution
United States of America North America| California United States of America North America| Arizona United States of America North America| Mexico North America| Sonora Mexico North America| Baja California Mexico North America|