Dalea elegans

  • Title

    Dalea elegans

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Dalea elegans Gillies ex Hook. & Arn.

  • Description

    90.  Dalea elegans Gillies

    (Plate LXXXIX)

    Herbaceous, suffruticose, or softly shrubby, variable (acc. to variety) in stature, (1) 1.5-12 dm tall, the stramineous, castaneous, or livid-purple stems densely tuberculate, either simple and monocephalous or subcorymbosely branched beyond middle, appearing glabrous up to the silky-barbate spikes but the stems at least when young and distally, the stipule-tips, and leaf-rachis (sometimes also the leaflets beneath) thinly pilosulous with weak spreading or sinuously subappressed hairs up to 0.15-0.8 mm long, the foliage green or subglaucescent, punctate beneath; leaf-spurs 0.4-1 mm long; stipules narrowly subulate, lance-caudate, or flexuously linear-setiform, (1.5) 2-8 mm long, glandular dorsally, pilosulous within; intrapetiolular glands 2, small, obtuse; post-petiolular glands prominent, a little larger; leaves subsessile or very short-petioled, the main cauline ones (1) 1.5-5 cm long, with narrowly margined, punctate rachis and (8) 10-16 pairs of gland-crenulate leaflets variable (acc. to variety) in size and texture, the upper rameal or spur-leaves, if present, shorter, with only (5) 7-11 pairs of smaller leaflets; peduncles (0.5) 1-7.5 cm long; spikes many-flowered, moderately dense, ovoid becoming oblong-cylindroid, without petals or androe- cia 10-14 mm diam, the flowers (pressed) falling into ± 3 ranks and exposing at least part of the pilosulous axis, this becoming 1-8 cm long; bracts persistent, (3.5) 4-7.3 mm long, the oblong-obovate or -elliptic, navicular body (2) 2.3-5 mm long, in profile (0.8) 1-1.6 mm wide, broadly scarious-margined in lower 2/3, livid-keeled and livid-glandular distally, either glabrous or pilosulous dorsally, ciliolate toward tip, contracted into a subulate livid inwardly pilosulous tail (0.7) 1.5-3 mm long; calyx 4.3-6.9 mm long, densely pilose-pilosulous with straight ascending hairs up to 0.4-1.2 mm long, the tube (measured to dorsal sinus) 2.7-3.4 mm long, the orifice oblique, the slender, commonly livid-nigrescent ribs little prominent, the flat membranous intervals charged with 1 (or the ventral pair with ± 2) rows of 3-8 minute, yellowish or transparent glands, the deltate to narrowly triangular-acuminate, minutely gland- spurred teeth unequal, the dorsal one 1.6-3.3 mm long (0.6-3.6 mm shorter than tube), the ventral pair shortest and broadest; petals variable (acc. to variety) in color, largely either bright blue or amethyst purple, the banner usually, the keel often, the wings rarely charged with small subapical glands, the blade of banner gland-sprinkled in eye, glabrous dorsally, the epistemonous petals perched low on androecium (± 1.2-2.3 mm above hypanthium; banner 6.4-8.3 mm long, the claw 2.7-3 mm, the deltate-cordate or suborbicular-flabellate, emarginate blade 4.1-5.2 mm long, 4.4-5.6 mm wide; wings 5.2-7 mm long, the claw 1.4-2.4 mm, the obliquely ovate or oblong- ovate blade 3.6-5.3 mm long, 1.9-2.8 mm wide; keel 8.4-9.7 mm long, the claws 2.7-4 mm, the broadly ovate-elliptic blades 5.5-6.7 mm long, 3-3.8 mm wide; androecium 10-merous, 8-10.3 mm long, the longer filaments free for 2.6-4.4 mm, the connective gland-tipped, the anthers 0.65-0.9 mm long; pod (little known) in profile obliquely triangular, 2.6-3 mm long, the style-base latero-terminal, the prow slenderly keeled, the valves hyaline in lower half, thence papery, sparsely gland-sprinkled, pilosulous; seed ± 1.6-2.1 mm long.

    In the context of its Andean relatives, the notable feature of D. elegans, sens, lat., is the high number of leaflets, ten to sixteen pairs in most primary cauline leaves. Only the naturalized annual D. leporina can match it in this respect. In arrangement and form of the flowers D. elegans closely resembles the Bolivian D. pazensis and D. kuntzei; it seems likely that these three species, which have preserved so many common charactersitics while attaining vicariant ranges, are derived from a common source. The only perennial native dalea entering the range of D. elegans is the high-montane D. boliviana, a smaller, humifuse plant with much shorter and simpler leaves.

    As defined herein, D. elegans is a polymorphic species, variable in stature, in amplitude of foliage, in pubescence, and in petal color. Burkart (1952, p. 253, fig. 66) recognized for Argentina, within the same span of variation, two major species, D. elegans sens. str. and D. onobrychioides, distinguished primarily by stature and size of leaflets, but these differences correlated with dispersal and ecology. The material that I have seen can generally be sorted neatly into categories, but there are difficulties: the ranges overlap in Salta, and there are disturbingly transient forms in southern Bolivia which cannot be ignored. Following Burkart with these reservations, it is possible to define a relatively low- growing, xerophytic var. elegans with short, crowded leaves, small, fleshy, folded leaflets, and petals of a reddish or amethystine purple (the banner mostly white in bud); and a taller, paniculately branching var. onobrychioides, characterized by expanded foliage of thinner texture and violet-blue petals (the banner concolorous distally). The former is proper to the arid sierras rising from the pampas east of the Andes proper; it ranges, mostly below 1900 m, from north-central San Luis through Sierra de Cordoba and reappears near Salta. From Salta northward, mostly at and above 2000 m, according to Burkart in more mesic environment, the species is represented by var. onobrychioides. Where this enters southern Bolivia, in Tarija, it has been redescribed as Parosela eosina. The type- collection of the latter shows in one and the same plant the low growth and small leaflets of var. elegans combined with the blue-violet petals of var. onobrychioides, but a second collection from the same region (Narvaez near Tarija, 2800 m., Cardenas 4941, US) retains the diffuse habit of var. elegans with the flat leaflets and flowers of var. onobrychioides. It appears that D. elegans preserves the habital plasticity which is so often encountered among its Peruvian kindred.