Dalea brachystachya

  • Title

    Dalea brachystachya

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Dalea brachystachya A.Gray

  • Description

    142.  Dalea brachystachya Gray

    (Plate CXXX)

    Low, slender or subfiliform herbs, commonly monocarpic, always flowering early the first year of growth and sometimes enduring into a second season, the root then lignescent but not over 3 mm diam, except for minutely ciliolate stipules glabrous to the spikes, with (1) 3-many, diffuse or both diffuse and assurgent, smooth or sparsely verruculose, pallid or purplish, simple or sparingly branched stems (0.5) 1-3.5 (4) dm long, thinly leafy and usually fertile from near middle upward, sometimes throughout or only terminally, the peduncles mostly leaf-opposed (but terminal to some ultimate branchlets and to primary stems when depauperate), the foliage pale green or commonly glaucescent, the leaflets smooth and yellowish above, often red- edged, paler and livid-punctate beneath; leaf-spurs almost 0; stipules subulate, narrowly triangular or subulate-attentuate, 0.8-2.5 mm long, becoming brown and fragile; intrapetiolular glands 0 or minute; post-petiolular glands small, sometimes prominulous, golden or livid; leaves short-petiolate, 8-25 (30) mm long, with narrowly margined, sparsely verruculose rachis and (1) 2-5 pairs of oblanceolate to linear- oblanceolate, emarginate, usually loosely folded leaflets 2-14 (16) mm long, the terminal one nearly always longer than the last pair, either sessile with them or shortly stalked and solitary; peduncles very slender or subfiliform, 1-7 cm long (rarely sub- obsolete), longer than the opposed leaf, often arched outward from the stem and abruptly incurved under the spike; spikes conic-ovoid becoming ovoid, globose, or shortly oblong, without petals 8-11 (12) mm diam, the hispidulous axis ultimately 3-16 mm long; bracts rather tardily deciduous, rhombic-ovate- to lance-acuminate or -caudate, 2.5-6 mm long, the lowest glabrous dorsally but ciliate below middle, the upper ones often thinly pilose dorsally, plumose-ciliate, all prominently glandular dorsally, commonly livid-purplish, glabrous within; calyx (3.5) 4.4-5.8 (6) mm long, densely pilose with straight spiral, at first forwardly subappressed, soon spreading hairs up to 0.7-1.4 (1.7) mm long, the tube (1.5) 1.6-2.1 mm, not recessed behind banner, the ribs brownish, prominulous, the membranous intervals charged with 1 row of ± 3 small, yellow or transparent, sometimes obsolete glands, the teeth triangular- aristate, gland-tipped and -spurred, at first erect, finally stellately divergent, the longest (1.5) 2.4-4 mm long, with rare exceptions longer than tube; petals pale but clear yellow, fading pinkish-brown or brownish-purple, usually eglandular, the epistemonous ones perched well below middle of androecium; banner 2-3.4, rarely 5.2-6 mm long, the ventrally sulcate claw 0.8-2 (2.4) mm, the deltate-ovate or -cordate blade mostly 1-2, rarely 4 mm long, about as wide, the basal lobes confluent across top of claw but hardly elevated to form a comet; wings 2.1-3.4 (4.8) mm long, the claw 0.8-1.5 (1.7-2.1) mm, the ovate-triangular blades 1-2 (2.9) mm long, 0.7-1.1 (1.6-1.8) mm wide; keel (2.6) 3-4.3 (5.8-6.2) mm long, the claws (1) 1.2-1.9 (2.8) mm, the oblong-ovate or -obovate blades 1.8-2.8 (3.8) mm long, 1.3-2 (2.4) mm wide; androecium (9) 10-merous, 3.5-5.5 (6.8) mm long, the longer filaments free for 1-1.4 (1.7 -2) mm, the connective gland-tipped, the pallid or yellowish anthers 0.3-0.45 (0.6) mm long; pod 2.3-2.6 mm long, in profile triangular-obovate, the style-base at or below the distal corner, the prow slightly dilated, green or becoming brown or livid, the valves hyaline in lower 1/2, thence thinly papery, pilosulous, sometimes obscurely gland-sprinkled; seed 1.4-1.7 mm long; 2n = 14 (B. L. Turner; Mosquin).— Collections: 62 (x).

    Desert grassland, cactus desert, mesquite-thorn scrub, or creosote (Larrea) desert, n.-ward entering high short-grass prairie, 1300- 2430 m (± 4300-8100 ft), widespread and locally abundant, especially but not exclusively on limestone, over the Mexican Plateau and the Chihuahuan Desert, from Aguas Calientes and San Luis Potosi n.-ward into s.-w. United States, extending from San Luis Potosi s.-e. through Hidalgo probably just into extreme n. Mexico and, apparently disjunctly, to the Tehuacan Desert in s.-e. Puebla; to be expected in Oaxaca (cf. discussion of D. lachnantha Schauer); in United States from trans-Pecos Texas (Davis Mts., Jeff Davis Co.) to s.-e. Arizona (Cochise, Santa Cruz, Pima cos.) and thence marginally into Sonora, in New Mexico n. up Rio Grande valley to n.-e. Socorro Co. and one old station (not verified recently) on the headwaters of the Pecos in San Miguel Co. — Flowering primarily August to November, sometimes again (or for the first time, following rains) April to June. — Representative: UNITED STATES. Arizona: Griffiths & Thornber 213 (NY); Barneby 2681 (NY); Blumer 1728 (L, NY). New Mexico: Rose & Fitch 17,645

    (NY, US); Barneby 13,837 (CAS, GH, NY, US); Metcalfe 772 (NY). Texas: Warnock 8042, 9298 (RENNER). MEXICO. Sonora: Thurber 1098 (F, NY). Chihuahua: Stewart & Johnston 2023, 2103 (GH, TEX); Pringle 601 (BR, F, NY, US), 347 (BR, F, MEXU, NY, UC); Gentry 8251 (MEXU, MICH, UC, US). Coahuila: Johnston & Mueller 993 (GH, TEX); Johnston 9412 (GH). Durango: Gentry 6876 (F, NY), 6888 (NY); Mosquin 6896 (DAO), 6904 (NY); Ripley & Barneby 14,193 (NY). San Luis Potosi: Purpus 5193 (F, NY, UC); Ripley & Barneby 13,313 (MEXU, NY, UC); Rzedowski 1850 (ENCB). Tamaulipas: Ripley & Barneby 14,772 (NY). Zacatecas: Ripley & Barneby 13,467 (CAS, MEXU, NY); Gentry 8535 (MICH, US). Aguas Calientes: Rose & Painter 7702 (NY, US). Queretaro: M. C. Johnston 2894 (TEX). Hidalgo: Pringle 8732 (F, L, M, MEXU, NY, TEX, UC, US, W, Z); Purpus 405 (UC); Gonzalez-Quintero 3048 (ENCB). Puebla: Purpus 1205 (F, NY, UC); Mosquin 6662 (NY); Miranda 4516 (MEXU).

    Dalea brachystachya (short-spiked) Gray, Pl. Wright. 2: 39. 1853 ("brachystachys").—"Valleys, in alluvial soil, between San Pedro and the Sonoita; Sept. ([C. Wright] 990)"—Holotypus, GH! isotypi, NY, US! — Parosela brachystachya (Gray) A. Hell., Catal. N. Amer. Pl. ed. 2, 113. 1900, nomen (without citation); Rose, Contrib. U. S. Nat. Herb. 10:105. 1906.

    Dalea lemmoni (John Gill Lemmon, 1832-1908) Gray, Proc. Amer. Acad. 17 : 200. 1882 ("Lemmoni"). — "Near Fort Bowie, Apache Pass, South Arizona [Cochise Co.], Lemmon, 1881." — Holotypus, Lemmon 563, GH! isotypus, NY! — Parosela lemmoni (Parry ex Gray) A. Heller, Catal. N. Amer. Pl. ed. 2, 6. 1900.

    An inconspicuous little plant, with slender, sparsely leafy stems and small heads of flower that become stiffly barbate as the fruits mature, each calyx resembling and functioning as a Composite achene and pappus. The species is the only one at once glabrous to the spikes, annual or short-lived perennial in duration, and yellow-flowered, and is therefore easily recognized, at least at anthesis. Unlike the majority of annual daleas, D. brachystachya is rarely weedy, although when it does happen to seed into roadside gravels it profits from the increased water run-off and grows fat and leafy. In undisturbed grassland the plants vary from very slender, with few monocephalous stems incurved-ascending from the root-crown, to many-stemmed and relatively coarse, each axis then bearing a succession of leaf-opposed spikes elevated on slender or almost threadlike peduncles. The bracts are at least incipiently dimorphic, those at base of the spike broader and less densely ciliolate than the interfloral ones, sometimes forming a sort of involucre. The calyx-teeth also vary considerably in length, but are seldom shorter than the tube and usually longer than the corolla. As the pods mature the calyx-teeth diverge into a star, the plumose ciliae at the same time spreading widely. At the time Gray described D. lemmoni he had for comparison with D. brachystachya only its type and some cultivated progeny. The differential characters of more slender habit, narrower leaflets, and longer, more plumose teeth can be seen now, in the context of our ample material, to be unreal criteria, as already inferred by Tidestrom (in Tidestr. & Kitt., Fl. Pl. Ariz. 181. 1941). The characters adduced by Rydberg (1920, p. 68) to separate the two species are effective only in separating more and less adult specimens. In fact, following Rydberg’s key, the mature plants grown at Cambridge from Wright’s original D. brachystachya would be identified as D. lemmoni.

    As already mentioned, the corolla of D. brachystachya is very small, the keel-blades only ±2-3 mm long, not or little exserted from between the calyx-teeth. The high measurements for corolla-parts given parenthetically in the foregoing description are derived from an unusually large-flowered (but otherwise normal) form that has been collected twice in the foothills of Sierra Madre in central Chihuahua (LeSueur 400, ARIZ; Ripley & Barneby 13,868, CAS, NY). Because this unusual plant occurs well within the range of typical small-flowered D. brachystachya, I interpret it as a minor variant, but it deserves further study.

    Outside its natural range D. brachystachya has appeared as a waif on chrome ore piles at Canton, Maryland (C. F. Reed 32,755 in Sept. 1953, herb. Reed.).

    The nomenclature of D. brachystachya will not be securely settled until the identity of D. lachnantha Schauer, 1847, is established. The protologue of the latter fits D. brachystachya very closely indeed, and I would gladly have adopted the epithet, except for one obstacle. The type of D. lachnantha was said to have been collected in Oaxaca, and we have no modern evidence that the species extends south of the Tehuacan Desert in southern Puebla. Many species with similar dispersal patterns over the arid highlands of north- central Mexico extend, continuously or interruptedly, into the drier intermountain valleys of central Oaxaca, and D. brachystachya, a species easily overlooked, could well be of their number. If and when it turns up in Oaxaca, the claims of D. lachnantha (listed in Appendix I, q. v.) will need reappraisal.