Dalea versicolor var. glabrescens

  • Title

    Dalea versicolor var. glabrescens

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Dalea versicolor var. glabrescens (Rydb.) Barneby

  • Description

    132e.  Dalea versicolor Zuccarini var. glabrescens (Rydberg) Barneby

    (Plate CXXI)

    Stems solitary or few together, usually virgately ascending, 3-15 dm tall, commonly glabrate in lower 1/3 and pilosulous distally, rarely glabrous almost to the spikes, in fall paniculately few-branched distally but developing in spring at least a few short- shoots terminating in abbreviated spikes; stipules 2-6 mm long; foliage most commonly silky-pilose or -pilosulous, gray or greenish, the leaflets sometimes glabrate above, the primary leaves sometimes glabrous; leaflets of primary cauline leaves 8-12 pairs, usually crowded, strongly carinate dorsally; spikes (12) 13-15 mm diam, the axis mostly 1-4 (5) or in spring 0.5-1 cm long; calyx (5.4) 6.4-8.2 mm, the tube 2.6-3.2 mm, the dorsal tooth (2.9) 3.4-5 mm long; epistemonous petals rose-purple, lilac-pink, or faintly pink-tinged; 2n = 28 (Mosquin). — Collections: 33 (ix).

    Thin stony soil of grama grassland, especially along draws and rocky ravines along the e.-foothills of Sierra Madre and plateau to the e., ascending w.-ward into sunny oak-woods, 1755-2325 m (5850-7750 ft), common and sometimes forming extensive colonies, apparently calcifuge, centr. Chihuahua to n.-e. Jalisco, n.-centr. Guanajuato, and s.-w. San Luis Potosi. — Flowering September to December, late March to May.—Representative: Chihuahua: Pringle 242 (F, MEXU, NY), 723 (BR, F, MEXU, NY, SD, UC, W); Correll & Gentry 22, 776 (RENNER). Durango: Palmer 32 (F, NY, UC), 811 (F, NY, UC); Ripley & Barneby 13,480 (CAS, MEXU, NY). Zacatecas: Ripley & Barneby 14,157 (NY); Mahler 5741 (NY). Aguas Calientes: McVaugh & Koelz 55 (MICH). Jalisco: Ripley & Barneby 14,136 (CAS, NY, UC), 14,517 (NY). Guanajuato: Ripley & Barneby 13,348 (CAS, NY, US), 13,377 (MEXU, NY, US). San Luis Potosi: Parry & Palmer 149, 155 (NY); Rzedowski 8398, 8548 (ENCB).

    Dalea versicolor Zucc. subsp. argyrostachya (H. & A.) var. glabrescens (Rydb.) Barneby comb. nov., based on Parosela glabrescens (balding) Rydb., N. Amer. Fl. 24: 106. 1920.— "Type collected in the region of San Luis Potosi, 1878, Parry & Palmer 150..."— Holotypus, US! isotypi, GH, NY! — Parosela lasiostachya var. glabrescens (Rydb.) Macbr., Contrib. Gray Herb., New Ser. 65: 19. 1922. Dalea glabrescens (Rydb.) Bullock, Kew Bull. 1939: 196. 1939.

    Dalea wislizeni (Friedrich Adolph Wislizenus, 1803-1889) Gray, Mem. Amer. Acad. II, 4 (Pl. Fendl. 1): 32. 1849. — "Llanos, in the Sierra Madre, w. of Chihuahua, Dr. Wislizenus."—Holotypus, labelled ‘Mts. w. of Chiricahui’, GH! Parosela wislizeni (Gray) Vail, Trans. N. Y. Acad. Sci. 14: 34. 1894. Dalea wislizeni subsp. wislizeni Gentry, Madrono 10: 240, pl. 20, fig. 3 (map). 1950.

    A graceful and characteristic plant of the grama grasslands of Mexico’s central plateau, coming into flower in fall when the grasses themselves are yellow and continuing into spring. The well-known autumnal phase takes the form of tall virgate stems at first densely clad in primary and fasciculate secondary foliage, forking beyond the middle into a few- branched panicle of silky spikes. The spring-flowering phase, less often collected, preserves the original architecture of the autumnal stage, but the stems are now almost bare of leaves and carry, below the remains of autumnal spikes terminal to the branches, a variable number of short or capitate inflorescences terminal to greatly condensed axillary short-shoots. The petals are usually pale, softly pinkish or lilac, rarely of more vivid hue.

    The var. glabrescens as defined here is equivalent to D. wislizeni subsp. wislizeni sensu Gentry (1950, p. 240, 242), with this reservation: the glabrescent or glabrate plants from San Luis Potosi which Rydberg distinguished as Parosela glabrescens are reevaluated as a minor variant of the ordinarily gray-silky D. wislizeni, coordinate with the glabrescent phases of var. argyrostachya and var. versicolor. In Sierra de Guanajuato there occur within a few miles of each other populations with all foliage pubescent in some degree and others (cf. Ripley & Barneby 13,358, NY) with lower leaves glabrous. Again a few miles northeastward appears P. glabrescens, with primary leaves glabrous or nearly so but puberulent axillary spurs. The transition is now well documented and imposes, at the varietal level, an unwelcome but mandatory change of epithet. The introduction into var. glabrescens of the glabrate phase raises a difficulty in separating what has been called D. wislizeni from the next variety, hitherto passing as Dalea lasiostachya. This has essentially the flower and inflorescence of var. glabrescens, but differs in its prevailingly shorter calyx and fewer leaflets. The two varieties are vicariant, the var. involuta (D. lasiostachya) replacing var. glabrescens in the more mesic environment of the Neo-volcanic Belt. In one count of each variety Mosquin found var. involuta diploid and var. glabrescens tetraploid, but more counts, especially of the critical glabrate phase of var. glabrescens, are obviously desirable.