Dalea lutea

Title

Dalea lutea

Authors

Rupert C. Barneby

Scientific Name

Dalea lutea (Cav.) Willd.

Description

130.  Dalea lutea (Cavanilles) Willdenow

(Plate CXV)

Bushy-branching and diffusely trailing suffrutescent herbs and shrubs up to 1 m, s.-ward from s. Mexico becoming taller or weakly arborescent and up to 4 m tall, highly variable in quantity, quality, and dispersal of pubescence, sometimes glabrous to the inflorescence but the stems and leaves usually ± densely pilosulous with ascending, antrorsely subappressed, rarely erect, straight or sinuous hairs up to 0.2-0.8 (1.2) mm long, the young branches sparsely tuberculate distally, the older stems becoming grayish-brown and furrowed, the herbage varying from deep green to canes- cent, often discolored to blackened in drying, the leaflets equally pubescent both sides, pubescent only below, or glabrous, brighter green above, livid-tuberculate beneath; leaf-spurs 0.3-1.2 mm long; stipules narrowly subulate to subulate-attenuate or linear-caudate, 1-8 mm long, castaneous or livid becoming dry and papery, dorsally pubescent or rarely glabrous; intrapetiolular glands usually 0, exceptionally 1 or 2, small, black; post-petiolular glands prominent, conic or mammiform, black or livid; leaves short-petioled or subsessile, the main cauline ones 1.5-5 (7) cm long, with narrowly margined rachis and 5-10 or (in one rare var.) 9-15 pairs of oblong-obovate to broadly oblanceolate or oblong-elliptic, obtuse to deeply emarginate, flat or loosely folded leaflets up to 3-14 mm long, the leaves of axillary spurs (when present) smaller, with fewer shorter leaflets; peduncles (of smaller plants) all terminal to stems, but usually the first leaf-opposed and succeeding ones terminal to lateral branchlets and raised above the first, (0) 0.5-5.5 (7) cm long; spikes ± dense but not conelike, usually many-flowered, ovoid-pyramidal early becoming cylindroid, without petals or androecia 0.9-1.5 cm diam, the pilosulous (exceptionally glabrate) axis (1) 1.5-10 (15) cm long; bracts persistent (deciduous with ripe pod) ovate- to lance-acuminate or -caudate, 3-6.5 mm long, rather firm, commonly livid or black, tuberculate, dorsally pilose or glabrous, most commonly bearing a few hairs at least on keel distally and on the tail, always glabrous within; pedicels 0-0.3 (0.5) mm long; calyx (3.6) 4-7 (7.7) mm long, the tube (2.2) 2.3-2.9 (3.2) mm long, often glabrous externally or glabrescent toward the base, sometimes pilose from base upward, the ribs slender becoming prominent, usually colored, the pallid or livid-nigrescent, in age ± lustrous intervals charged with 1 row of ± 3-5 round, elliptic, or linear, black or livid blister-glands up to 0.2-1 mm diam, the plumose teeth stiffly aristate above the low-deltate to broadly triangular base, commonly gland-spurred, unequal, the dorsal one longest, (1.3) 1.7-4.5 (5.2) mm long, (1) 0.6 mm shorter to 1.2 (2.7) mm longer than tube, in fruit divaricate and often slightly declined at tip; petals concolorous, pale yellow, clear lemon-yellow, or greenish-ochroleucous, at least the banner rubes- cent in age, the epistemonous ones either unchanged in drying or turning brownish (especially along nerves) or finally black (even before falling), the banner and keel often but not always gland-tipped, the banner-blade sometimes gland-sprinkled, the inner ones perched low on androecium (0.8-2.7 mm above hypanthium; banner 4.6-7.5 (8) mm long, the claw 2-4 mm, the deltate-ovate or cordate blade ± hooded at the obtuse or emarginate apex, (2.6) 2.8-4.8 mm long, 2.8-4.5 (5.4) mm wide, recessed at base into a ± pronounced cornet; wings 4.7-7.8 mm long, the claw 1.4-2.6 (2.8) mm, the oblong-elliptic or -obovate blade 3.3-5.2 (5.6) mm long, 1.4-2.6 (3) mm wide; keel 6.4-10.5 mm long, the claws 2.1-4.2 mm, the broadly obovate to obliquely long-obovate blades (4.2) 4.5-7.1 (7.3) mm long, 2.4-4 (4.5) mm wide; androecium 10-merous, 6.5-10 (10.5) mm long, the longer filaments free for 1.4-2.6 (3.1) mm, the tassel often but not always nigrescent; pod 2.4-3.1 mm long, either triangular or obovate in profile, the style-base terminal or latero-termmal, the slenderly carinate prow either straight or convexly arched, the valves hyaline at base, thinly papery, often nigrescent and charged with at least a few livid glands, densely pilosulous from middle upward or only thinly so toward the prow; seed 1.6-2.1 mm long.

A polymorphic species widely dispersed over much of temperate Mexico and south through the highlands of Guatemala into Honduras, D. lutea is subject to notable variation in stature and pubescence, but in other respects is rather uniform. The species can be separated from other yellow-flowered daleas by the combination of persistent bracts and a long-toothed calyx with prominent blackish glands in the intercostal panels of the tube and plumulose teeth. It is readily divided into two major branches, one adapted to the arid plateau north of the Neovolcanic Belt, the other to the oak-pine belt south of that line. These differ most obviously in stature, the former flowering as a herb or low bush little more than 1 meter tall, whereas the other becomes a tall straggling shrub or treelet that may reach a height of four meters in favorable sites. The difference in habit is correlated weakly with differences in distribution of vesture, size of stipules, and size of petals, and with a perhaps more stable one in outline of the pod. A poorly understood entity, D. lutea var. arsenei, known from two mutually remote localities at the margins of Balsas Depression, is apparently distinguished from both the preceding in the combination of many leaflets and larger flowers.