Chamaecrista serpens var. wrightii

  • Title

    Chamaecrista serpens var. wrightii

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Chamaecrista serpens var. wrightii (A.Gray) H.S.Irwin & Barneby

  • Description

    26e. Chamaecrista serpens (Linnaeus) Greene var. wrightii (Gray) Irwin & Barneby, stat. nov. Cassia wrightii Gray, Pl. Wright. 2: 50. 1853.—"Hillside, on the Sonoita, near Deserted Rancho, Sonora [now Santa Cruz Co., Arizona]; Sept. (1034)."—Holotypus, Wright 1034, GH! isotypi, K, NY, US!—Chamaecrista wrightii (Gray) Wooton & Standley, Contrib. U.S. Nat. Herb. 19: 335. 1915; Pennell, 1917, p. 342 (as comb. nov.).

    Cassia palmeri S. Watson, Proc. Amer. Acad. 22: 408. 1887.—"Rio Blanco [near Guadalajara, Jalisco]; June [1886]. (29.)."—Holotypus, GH! isotypi, G, LE, NY (2 sheets), US (2 sheets, one labelled "Barranca near Guadalajara")!—Chamaecrista palmeri (S. Watson) Greene, Pittonia 3: 242. 1897; Britton & Rose, 1930, p. 242.

    Chamaecrista mazatlensis Rose ex Britton & Rose, N. Amer. Fl. 23(5): 283. 1930.—"Vicinity of Mazatlán, Sinaloa, March 31, 1910, Rose, Standley & Russell 13824 "—Holotypus, US! isotypus, NY!

    Chamaecrista ortegae Britton ex Britton & Rose, l.c. 1910.—"Capule, Mazatlán, Sinaloa, 200 m. altitude, 1925, J. G. Ortega 6088.—Holotypus, US! clastotypus + photo, NY!

    Chamaecrista mexiae Britton ex Britton & Rose, op. cit. 284. 1930.—"Between Yxtlan and Barranca del Oro, 1480 m. altitude, Nayarit, September 27, 1926, Ynes Mexia 790."—Holotypus, US! isotypi, A, CAS, GH, NY!

    Chamaecrista chiapensis Britton & Rose, l.c. 1930.—"Rocky soil, Monserrate, Chiapas, May, 1925, Purpus 10592."—Holotypus, NY! isotypus, US!—Cassia monserratensis Lundell, Phytologia 1: 215. 1937 (non C. chiapensis Standley, 1919).

    Chamaecrista alamosensis Britton & Rose. l.c. 1930.—"Sierra de Alamos, Sonora, March 18, 1910, Rose, Standley & Russell 13046."—Holotypus, US! isotypus, NY!

    Cassia wrightii sensu Bentham, 1871, p. 571; Pollard, 1894, p. 217; Kearney & Peebles, 1951, p. 406. Chamaecrista wrightii sensu Britton & Rose, 1930, p. 286.

    Stems mostly (1—) 1.5—4 dm, in desert environment weakly suffrutescent basally; vesture highly variable, the stems and petioles thinly incurved-pilosulous or thinly to very densely hispid with erect or subretrorse septate setae; larger lvs 2-3.5(-4) cm; petiole, (including pulvinus) 2-4 mm; gland l(-2, and rarely 1 or more on rachis), 0.2-0.5 mm diam, the stipe (0.2-)0.3-l mm; lfts of larger lvs (6—)7— 10(— 12) pairs, up to 5— 10(— 12) x 1.5—2.5(—3) mm, either olivaceous both sides or cinnamon-brown dorsally; fls large, the sepals up to 8— 12(—13.5) x 3-5.5 mm, the cucullus 13—19(—20) mm long; longer anthers 6-9.5 mm; style 6-10 mm; pod mostly 2.5-3.5(-4) mm, 6-ll(-12)-ovulate.—Collections: 53.

    Dry hillsides, often in grassy places, extending from the coastal plain upward through short-tree forest into the pine-oak belt, 10-2100 m, locally plentiful along the Pacific slope of Sa. Madre Occidental from s. Arizona (Santa Cruz Co.) to centr. Jalisco and s.-e. locally and interruptedly to Sa. Madre del Sur in Guerrero, s.-w. México, and highland Chiapas, unknown as yet from Michoacán, Morelos, or Oaxaca.—Fl. (VI-)VII-I, exceptionally later.

    Like var. serpens itself, the large-flowered var. wrightii varies greatly in density and proportions of the short incurved and long setose vesture and to considerable degree likewise, but independently, in the diameter of the petiolar gland and development of its stipe. The pubescence varies in a clinal mode, setae being absent or almost so (C. wrightii sens, str.) from Arizona south into Sinaloa (that is, within and around the periphery of the Sonoran Desert) and thence southward become increasingly long and many (C. palmeri sens, str.), culminating in a densely hirsutulous minor variant known from a few collections from s.-w. Durango (Rose 2253, 3482). Many collections of var. wrightii are characterized by a bright cinnamon-brown discoloration of the lower leaf-surface, but this sometimes appears erratically on only some leaves, or on only some plants of a population, and has no taxonomic value. Two of the three known collections from Sa. Madre del Sur differ slightly either in abnormally assurgent branches (Hinton 10536) or unusually many (-12) pairs of leaflets, but seem to represent no more than minor variants. The Chiapas populations, described by Britton & Rose as a species supposedly distinguished by the combination of strongly veined leaflets with submarginal costa, a short-stipitate gland, and relatively short pedicels, really do have prominently and closely venulose and narrow leaflets, but are otherwise matched at all points by distantly allopatric forms of var. wrightii. The types of Ch. alamosensis and Ch. mazatlensis were both collected in March, that is at the height of the dry season, and have lost their larger leaves in consequence; no structural differences from sympatric var. wrightii collected in the vigor of new growth can be detected. Despite the fact that Britton referred Ch. mexiae and Ch. palmeri to different groups, supposedly separable by leaf-texture, we can find no substantial difference between the types, collected at points in the río Santiago valley about 100 km apart in Jalisco and adjoining Nayarit respectively.