Monographs Details: Dalea humifusa Benth.
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.
Scientific Name:Dalea humifusa Benth.

93.  Dalea humifusa Bentham

(Plate XC)

Dwarf, humifuse and matted or diffusely trailing herbs developing in age a freely forking, irregularly radicant caudex, the year’s growth 2-20 cm long, the young stems, foliage, and stipules pilosulous with ascending or subappressed hairs up to 0.3-0.7 mm long, the leaves when small silvery when larger greenish-cinereous, the leaflets commonly pubescent both sides, sometimes medially glabrescent or glabrous above, brown-punctate beneath; leaf-spurs up to 1 mm long; stipules narrowly ovate to lance- subulate, 1-2.2 mm long, green, brown, or livid, becoming papery; intrapetiolular glands spiculiform, often concealed by hairs; post-petiolular glands small, obtuse, little prominent; leaves mostly subsessile, the main cauline ones (5) 7-16 mm long, with narrowly margined rachis and 2-5 pairs of oblanceolate or linear-oblanceolate, subacute, obtuse and apiculate, or obtuse, loosely or tightly folded, dorsally keeled leaflets (2) 2.5-5 (6) mm long; peduncles, except the first of each main axis, terminal to leafy branchlets, commonly 0-2 cm, sometimes 1-5 cm long; spikes moderately dense, bluntly ovoid or subglobose becoming ovoid or cylindroid, without petals 6-7 mm diam, the pilosulous axis finally (3) 5-25 mm, sometimes 20-35 ( 40) mm long; bracts persistent, (2) 2.5-4.2 mm long, the body broadly ovate or obovate, firm almost throughout or chiefly along keel and distally, narrowly scarious-margined, (1.8) 2-3.2 mm long, dorsally gland-verruculose and pilosulous at least beyond middle, at apex truncately or cuneately contracted into a subulate tail (0.2) 0.4-1 mm long; calyx 2.6-3.7 mm long, pilosulous either from base upward or only about the teeth with fine ascending hairs up to 0.4-0.9 (1) mm long, the ovoid-campanulate tube 1.9-2.4 mm, slightly recessed behind banner, the filiform ribs scarcely prominent, the membranous intervals charged with 4-10 small 1-seriate (or in adaxial intervals scattered) glands, the triangular-apiculate, often minutely gland-spurred, distally green or livid teeth scarcely unequal, the dorsal one 0.6-1.3 mm long (0.7-1.7 mm shorter than tube); petals commonly bicolored (rarely all white), the banner white, sometimes with blue corners, gland-tipped and -sprinkled, rubescent, the epistemonous ones blue, rarely purple or lilac, perched below middle of androecium (1.2-2 mm above hypanthium), at least the keel gland-tipped; banner 3.5-5.1 mm long, the claw (1.2) 1.5-2.8 mm, the broadly ovate-cordate obtuse hooded blade 2.1-3.1 mm long, 2.2-3.2 mm wide, plane at junction with the claw; wings 2.5-4 mm long, the claw 1-1.5 mm, the ovate or oblong, often scarcely auriculate blade 1.6-2.7 mm long, 0.9-1.5 mm wide; keel 3.3-4.8 mm long, the claws 1.1-1.8 mm, the ovate-elliptic blades (2.1) 2.3-3.1 mm long, 1.3-2 mm wide; androecium 10-merous, 4.2-5.5 (5.8) mm long, the longer filaments free for 1-1.6 (2) mm, the connective gland-tipped, the pale blue anthers 0.3-0.5 mm long; pod obliquely obovoid, 2.1-2.4 mm long, the style-base latero-terminal, the prow slightly thickened, the valves hyaline in lower half, thence thinly papery, hirsutulous, gland-sprinkled; seed brown, sometimes purple-dotted, 1.5-1.6 mm long.— Collections: 30 (o).

Pumice plains and piedmont slopes of the great volcanoes of the Ecuadorean Andes, mostly 2400- 2850 m, descending along river-banks or on outwash gravels to 1680 m (possibly lower), from e. Imbabura s. through the central valleys of Pichincha, Cotopaxi, and Tungurahua to the n. slope of Mt. Chimborazo (lat. 0° 30 N-l° 45 S).—Flowering almost throughout the year .—Representative: Pichincha: Jameson 20 (NY), 823 (OXF, US); Asplund 6679 (NY, US); Wiggins 10,567 (NY). Cotopaxi: F. C. Lehmann 4789 (F, US). Tungurahua: A. S. Hitchcock 21,735 (NY, US); G. W. Prescott 371 (NY). Chimborazo: Spruce 5840 (F, K, NY, OXF); Rimbach 64, 87 (F, NY, US); Asplund 5944 (F, US).

Dalea humifusa (prostrate) Benth., Pl. Hartw. 170. 1845.-"In planitie Rumibamba prope Quito."-Holotypus, Hartweg 954, K (herb. Benth.)! isotypi, F (fragm.), OXF, US, isotypus formerly at B survives as Field Neg. 2034 (F, NY)! — Parosela humifusa (Benth.) Macbr., Contrib. Gray Herb., New Ser. 65: 23. 1922.

Parosela humifusa var. anatona (stretched upward, taller) Macbr., Field Mus., Bot. 4: 105. 1927. — "ECUADOR: near Riobamba, 1922, Mille 60..." — Holotypus, collected by Fr. A. Mille, S. J., US! clastotypus (fragm.), F!—Dalea humifusa var. anatona (Macbr.) Macbr., Candollea 7: 223. 1937.

The only prostrate dalea known from the highlands of Ecuador, notable for the small size of leaf and flower. The typical form, collected by many visitors to the Equatorial Monument near Quito and elsewhere on the pumice plains of the central valley, is a truly humifuse, suffruticulose, closely matted plant with small crowded leaves, each composed of 2-4 pairs of leaflets silvery on both sides. The spike is ordinarily short and shortly pedunculate, therefore hardly emerges from the foliage, the calyx is ordinarily pilosulous from base upward, and the epistemonous petals are usually vivid blue. Color variants, from paler blue through shades of purple to pure white, are known (cf. Paredes 2, 2' 2", NY), and forms with greener, less pubescent leaves. In the foothills of Mt. Chimborazo near Riobamba a form with calyx glabrescent or even glabrous up to the always pubescent teeth is associated with the typical form; the leaflets here are green above, often obtuse. Two variants collected in quantity by Spruce have been widely distributed under unpublished varietal ("microstachya") or specific ("radicata") names, and one of them was described by Macbride as var. anatona, this with somewhat longer, more obviously suffruticulose caudex and longer spike and peduncle, perhaps the product of a sheltered habitat. In the Department of Imbabura, at its northern limit, D. humifusa descends on river gravels and outwash plains of Rio Chota as low as 1640 m (Andre 3550, F, K) and loses its closely matted habit although retaining its cinereous vesture. The species appears to be plastic in habit of growth, but stable in size and form of flower.

Narratives:Dalea humifusa