Dalea prostrata
Rupert C. Barneby
158. Dalea prostrata Ortega
(Plate CXL)
Prostrate perennial herbs with several or many slender, pliantly humifuse stems (0.7) 1-4 (5) dm long radiating from the often shallowly subterranean crown of a forking woody root (yellow beneath the bark), ± densely pilose-pilosulous almost throughout with fine straight hairs up to (0.7) 1-1.7 (2.2) mm long, the vesture variable in density and orientation, the hairs of stems varying from ascending or subappressed to vertical or subretrorse, of leaves widely ascending to subappressed, the stems very slender at base becoming stouter distally, simple and monocephalous or few-branched above middle and the lateral branchlets each monocephalous, the sessile spikes standing vertical to the ground, the foliage ± bicolored, the leaflets (dried) yellowish- or verdigris-green and either glabrous or pubescent above, sparsely punctate and more densely pubescent beneath; leaf-spurs 0.5-1 mm long; stipules sub- membranous, narrowly subulate to linear-lanceolate or -caudate, 2-5.5 (7) mm long, thinly pilose dorsally, becoming dry but not stiff; leaves petioled, 0.5-3 cm long, the petiole broadly margined, often punctate, the rachis 0.5-2.5 mm long, the leaflets mostly 3, rarely 4 or 5, obovate to elliptic, oblanceolate, oblong, or rhombic-oblanceo- late, acute, rarely linear-elliptic, obtuse and mucronulate, or (when broad) shallowly emarginate, (3) 4-20 mm long, either flat or loosely folded; spikes moderately dense, ovoid becoming oblong-cylindroid, without petals 1.6-2 cm diam, the ribbed, densely pilosulous axis becoming (1) 1.5-7 cm long; bracts subhomomorphic, deciduous at or soon after anthesis, oblong- to broadly lance-acuminate or caudate, 6-12 mm long, in lower submembranous pallid navicular, embracing the calyx, thence green, livid, or purple, dorsally glabrous or thinly pilose, often sparsely gland-punctate, plumose-ciliate; calyx 6.3-8.6 mm long, pilose with fine straight spreading spiral hairs up to 1.5-2.3 (2.7) mm long, the tube thinly so, (2.5) 2.7-3.6 mm long, 2.8-3.5 mm diam, the ribs becoming thick and prominent, the flat membranous intervals charged with 1 row of 2-4 small, mostly transparent glands, the narrowly triangular- to lance- aristate red- or livid-tipped teeth (3.3) 3.7-5.8 mm long, stellately divergent in fruit; petals yellow, fading orange-brown, or (dried) pinkish-brown, eglandular, the epistemonous ones perched below middle of androecium, 1.5-4 mm above hypanthium; banner (4.7) 5-7 mm long, the claw (2.7) 3-4 (4.6) mm, the deltate-cordate, obtuse blade 2-3.5 mm long, 3.5-4.2 mm wide, recessed at base into a comet; wings 7-8.2 mm long, the claw 2.2-2.8 mm, the obliquely obovate or oblong-elliptic blade 4.7-5.8 mm long, 2.7-4 mm wide; keel 8.6-11.3 mm long, the claws 2.3-3.5 mm, the broadly obliquely obovate blades (5.9) 6.3-7.8 mm long, (3.3) 3.6-4.3 mm wide; androecium 10-merous, 10.5-13 mm long, the longer filaments free for ± 3-4 mm, the pale anthers (0.8) 0.9-1.2 mm long; pod (of the section) 2.7-3.5 mm long; seed (seldom seen) yellow-green turning ochraceous, smooth and lustrous, 1.8-2.2 mm long; 2n = 14 (Mosquin). — Collections: 52 (vii).
Plains and hillsides, characteristically in arid grassland, 1400- 2700 m (4650-9000 ft), widespread and locally abundant on a variety of volcanic and sedimentary soils around the w. and s. margins of Meseta Central, from s.-e. Chihuahua (mpos Hidalgo del Parral and V. Matamoros) s. through Durango, Zacatecas, the n.-e. arm of Jalisco, and Guanajuato to extreme n. Michoacan (near Morelia) and the Valley of Mexico (Mexico Edo and D. F.), n. through Hidalgo and Queretaro into centr. San Luis Potosi (mpo Guadalcazar); somewhat isolated on the Gulf slope of Sierra Madre Oriental, at ± 1000 m, in s.-w. Tamaulipas (mpo. Jaumave). — Flowering July to November. —Representative: Chihuahua:r= Ripley & Barneby 13,906 (CAS, MEXU, NY). Durango: Palmer 638 (F, NY, UC, US); Gentry 6862 (F, NY). Zacatecas: Purpus s. n. in 1903 (UC); Guzman s. n. in 1959 (ENCB), Aguas Calientes: Hartweg 55 (L, NY, W); McVaugh 23,723 (MICH). Jalisco: Rose 2517 (NY, US). Guanajuato: Ripley & Barneby 13,342 (CAS, MEXU, MICH, NY, US); Purpus 481 (UC). Michoacan: Arsene 2476 (L, NY). Mexico: (Edo & D. F.): Pringle 4483 (BR, F, M, NY, US, W, Z); Bourgeau 71 (BR, M, P); Balls 5589 (K, UC, US); Rzedowski 17,112 (ENCB, WIS). Hidalgo: Purpus 1375 (F, NY, US); Rose & Painter 7704 (NY, US). Queretaro: Waterfall 13,928 (F, OKLA). San Luis Potosi: Parry & Palmer 165 (BR, F, NY, US); Ripley & Barneby 13,778 (CAS, NY). Tamaulipas: Viereck 847, 987 (US).
Dalea prostrata (prone) Ort., Decades 69. 1798. — "Habitat in Nova Hispania. Floret Novembri et Decembri in Horto Reg. Matrit. e seminibus missis per D. Sesse." — No typus survives at MA, but the protologue decisive.
Dalea triphylla (3-leaved, the leaves 3-foliolate) Sesse & Moc. ex G. Don, Gen Hist. Diehl. Pl. 2: 224. 1832. Native of Mexico...(v.s. herb. Lamb.)." —Presumed holotypus, labelled "Dalea triphylla sp. nov. de Mexico," OXF! probable isotypi are cited under the next .—Parosela triphylla (S. & M.) Macbr., Contrib. Gray Herb., New Ser. 65: 18. 1922.
Dalea trifoliolata (with 3 leaflets) Moric., Mem. Soc. Geneve 6: 531, tab. III. 1833.—"Hab. in Mexico...J’en possede des echantillons envoyes du Mexique par M. Alaman, d’autres recueuillis par M. Berlandier, dans la vallee de Tolucca, et j’en ai recu un de M. Pavon, sous le nom de Dalea triphylla, ined., que j’ai cru devoir modifier." — Lectotypus, labelled "Dalea triphylla R. & P. Nouvelle Espagne", G! isotypus, ‘Dalea triphylla herb. Pavon", P! paratypi, "Mexique, M. Allaman, 1832", G! and Berlandier 1214, G, W! — Dalea triphylla Pavon ex Schlechtd., Linnaea 12: 289. 1838, an illegitimate substitute for D. trifoliolata Moric., the supposed obstacle, D. trifoliata Zucc., illusory. — Parosela triphylla (Pavon ex Schlechtd.) Rose, Bot. Gaz. 40: 144. 1905. P. trifoliolata (Moric.) Rydb., N. Amer. Fl. 24: 98. 1920.
Over most of its range the aptly chosen epithets prostrata and triphylla (or trifoliolata) that have been applied to this species are tantamount to a diagnosis. In southern Chihuahua it is marginally sympatric with D. jamesii, distinct in its shorter, stiffer, more or less tufted stems, more silvery foliage, and yet longer calyx-teeth (cf. key to sect. Cylipogon, supra); and where it approaches Sierra Madre Oriental in Queretaro and San Luis Potosi it enters the range of D. luisana, akin but much smaller-flowered. The stems of D. prostrata, closely clad their whole length with short-petioled trefoil leaves, are not merely horizontally diffuse but weak and truly humifuse, radiating from a buried root-crown and winding through the grass to bear at their tips silvery-white, egg-shaped heads of plumose calyces that seem to start as it were directly from the ground.
The species varies in pubescence, in outline of leaflets, and size of bracts. Around the edge of Meseta Central from Chihuahua to Queretaro the stems are usually densely pilose with vertical or slightly retorse hairs; in the Valley of Mexico more weakly pilose. Leaflets vary from thinly pilose to glabrous on the upper face, and in outline from obovate obtuse to oblanceolate acute. The tips of the bracts may be as long or shorter than the body, and vary furthermore from pilose to glabrous dorsally and in color from pale green to livid or lively purple, when highly colored forming a sharp contrast with the clear yellow of the petals.
The identity of Dalea prostrata, listed by Rydberg as a doubtful synonym of Parosela trifoliolata, cannot be affirmed with certainty, no specimen of the original stock cultivated in the Madrid Garden having survived. However, the original description, calling for a prostrate herb with pilose stems, ternate (some 4-5-nate) leaves glabrous above, and spikes of yellow flowers subtended by concave bracts as long as themselves, answers to no other known species. The spikes were said to be pedunculate and recurved, which is not true of D. prostrata, though the abrupt curve of the stem which brings the head to vertical might suggest the latter character. Moricand, in any case, separated his D. trifoliolata because of its always ternate leaves and sessile spikes, and Macbride (1922, 1. c.) raised the same points when he adopted for the species the combination Parosela triphylla. Since occasional 4- and 5-foliolate leaves are found in wild specimens of D. prostrata, the presence of a peduncle is the only discordant note in the protologue, and cannot weigh heavily against all the positive evidence. Bentham was the first (Pl. Hartw. 10. 1839), soon followed by Schauer (Linnaea 20: 745. 1847), to voice the suspicion that D. prostrata and D. trifoliolata were one and same, and in the context of contemporary knowledge of sect. Cylipogon it seems virtually certain. All of the names proposed for the species rest ultimately on specimens or progeny of seeds sent to Madrid by Sesse, who is not known to have encountered any other member of the group.
References: [Article] 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.Multimedia:
