Dalea erythrorrhiza

Rupert C. Barneby

8.  Dalea erythrorrhiza Greenman

(Plate XXXII)

Slender diffuse or prostrate herbs from a vertical or obliquely forking root and small knotty root-crown at soil-level, appearing glabrous up to the villous-barbate inflorescence but the upper edges of the leaf-rachis and the stipules thinly pilosulous-ciliolate with weak spreading hairs, the few (mostly 2-6) remotely leafy, castaneous or livid, simple or few-branched, low-tuberculate stems (1.5) 6-35 cm long, floriferous upward from near middle, the foliage subglaucescent, the leaflets pallid above, punctate beneath; leaf-spurs 0.5-1 mm long; stipules lance-subulate, castaneous or livid, becoming papery, 1.5-3 (3.5) mm long; intra- and post-petiolular glands prominent, rounded; leaves slender-petioled, (1) 1.5-5(6) cm long, with scarcely margined rachis and 4-7 pairs of obovate- or oblong-cuneate, truncate-emarginate to openly retuse, thick-textured, flat or loosely involute leaflets (2) 3-9 (11) mm long, their margins elevated but scarcely undulate; peduncles both leaf-opposed and terminal, 0-3 cm long; racemes moderately dense, ovoid or ovoid-ellipsoid becoming oblong-cylindroid, 14-18 mm diam, the flowers declined after anthesis, the glabrous axis finally (1) 1.5-5.5 cm long; pedicels 0.3-0.9 mm long, the prickle-shaped subtending glands 0.2-0.4 mm long; calyx 5.8-7.1 mm long, villous with fine, straight, stiffly spreading spiral hairs up to 2.7-4 mm long, the tube 2.3-2.7 mm long, pleated, the purple-tinged ribs becoming prominent, the rather firm but (seen from within) membranous intervals charged with 1 row of 3-5 small transparent glands, the deltate-aristiform teeth subequal, 3.5-4.7 mm long, charged with 1-4 pairs of gland-spurs, plumose; petals blue (purplish when dried), all charged at base of blade with a cluster of small orange glands, the epistemonous ones perched within db 1 mm of hypanthium, the banner (detached) usually longest, all (in situ) shorter than the calyx-teeth; banner (4.9) 5.4-6.5 mm long, the claw (2.1) 2.3-3.1 mm, the ovate or ovate-oblong, entire, scarcely cordate blade 2.9-3.7 mm long, 2.4-2.8 mm wide; wings 4.7-5.7 mm long, the claw 1.4-1.9 mm, the narrowly oblong or lance-oblong blade 3.1-3.8 mm long, 1.2-1.5 mm wide, scarcely auriculate at base; keel 4.7-5.8 mm long, the claws 1.62.4 mm, the narrowly (subsymmetrical) ovate-oblong blades 2.7-3.7 mm long, 1.5-1.8 mm wide; androecium 10-merous, 5.5-7 mm long, the longer filaments free for 2.23 mm, the connective glandless, the anthers 0.4-0.5 mm long; pod 2.5-6 mm long, in profile broadly obliquely cuneate, the style-base latero-terminal, its prow laterally dilated, 0.6-0.8 mm wide, glabrous, the valves hyaline at base, papery, pilose and glandless distally; seed (seldom seen) 2.1-2.3 mm long; 2n = 14, 7 II (Mosquin). — Collections: 15 (v).

Low hills, knolls, eroded stream-banks, in grama grassland, sometimes with mesquite, 1550-2500 m (5200-8200 ft), mostly on eruptive, rarely calcareous substrates, local but forming colonies, Meseta Central of Mexico from s.-centr. Chihuahua (mpos Cd. Camargo and Hidalgo del Parral) s.-e., mostly e. of the Sierra Madre piedmont, through Durango, Zacatecas, and Aguas Calientes to n. Guanajuato (mpo S. Miguel de Allende) and n. San Luis Potosi (mpo Charcas).— Flowering June to November.— Representative: Chihuahua: Ripley & Barneby 13,929 (CAS, MEXU, MICH, NY, US). Durango: Mosquin et al. 6910 (NY); Palmer 293 (F, NY); Ripley & Barneby 14,164 (DAO, DS, NY). Zacatecas: Gentry 8536 (UC); Ripley & Barneby 13,469 (MEXU, NY), 14,144 (CAS, DAO, NY). Aguas Calientes: Rose & Painter 7703 (F, NY, US); McVaugh 23,682 (MICH, NY). San Luis Potosi: Lundell 5085 (ARIZ, NY). Guanajuato: Kenoyer 2189 (GH).

Dalea erythrorrhiza (with red root) Greenm. in Zoe 5: 185. 1904. — "Mexico. State of Durango: near the city of Durango, April to November, 1896. Dr. Edward Palmer, No. 486 (hb. Gr.). State of Zacatecas; in gravelly soil, near the city of Zacatecas...August, 1903, C. A.Purpus, No. 452..." — Holotypus (Palmer 487), GH! isotypi, F, NY, UC; paratypus (Purpus 452), GH!—Parosela erythrorrhiza (Greenm.) Rose, Contrib. U. S. Nat. Herb. 10: 105. 1906.

This is one of a small company of daleas, not closely related but alike in their humifuse habit, found on the thin prairies of the Mexican Plateau, drought-resistent plants that continue to grow and flower, with some loss of stem leaves, long after the grasses have turned sere and yellow. Among them D. erythrorrhiza is recognized at anthesis by the large membranous glabrous bracts that form a sort of imbricated cap on the young racemes, by the blue petals all shorter than the long-hispid calyx-teeth, by the overlapping keel-blades, and later on by the pod’s broadly dilated, glabrous prow. In form of the raceme and flower D. erythrorrhiza can be compared only with D. lachnostachya, which replaces it as the plateau dips northward into the Chihuahuan Desert. It is a much less showy plant than its relative, its distantly leafy, red or livid stems, creeping inconspicuously through the thin turf or over gravel colored like themselves, being hard to see until furnished with the turrets of hispid calyces.

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.

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