Senna hirsuta var. glaberrima

  • Title

    Senna hirsuta var. glaberrima

  • Author(s)

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna hirsuta var. glaberrima (M.E.Jones) H.S.Irwin & Barneby

  • Description

    138e. Senna hirsuta (Linnaeus) var. glaberrima (M. E. Jones) Irwin & Barneby, Phytologia 44(7): 499. 1979. Cassia leptocarpa var. glaberrima M. E. Jones, Contrib. W. Bot. 12: 7. 1908.—"Huachuca, Catalina, and Santa Rita Mts., Arizona, Aug. 1903."—Lectoholotypus, Jones s.n., 22.VIII.1903 (fl, fr) from Santa Rita Mts., POM! paratypus, Jones s.n., 18.VIII.1903 (fl) from Sabino Canyon, Catalina Mts., POM!—Ditremexa glaberrima (M. E. Jones) Britton & Rose, N. Amer. Fl. 23(4): 256. 1930.

    Cassia gooddingii A. Nelson, Amer. J. Bot. 23: 268. 1936.—. . secured by Mr. Leslie N. Goodding: No. 289 . . . Huachuca Flats, Arizona, August 2, 1909; no. 2431, Miller Canyon, Arizona, August 23, 1907 . . —Holotypus, Goodding 289, WYO (not seen); isotypus, NY! paratypus, Goodding 2431, NY!—Equated with C. leptocarpa var. glaberrima by Kearney & Peebles, 1942, p. 424.

    Cassia leptocarpa sensu Bentham, 1871, p. 531, quoad Wright 1032, non alibi; Wooton & Standley, Contrib. U.S. Nat. Herb. 19: 334. 1915.

    Cassia leptocarpa var. glaberrima sensu Kearney & Peebles, Ariz. Fl. 405. 1951.

    Pubescence inconspicuous, sparse or distally almost 0, of appressed or subappressed hairs up to 0.15-0.35(-0.4) mm, the lfts varying from glabrous minutely ciliolate to puberulent on both faces, the foliage commonly smaller, brighter green and of firmer texture than that of var. hirta, the fl-buds either glabrous or puberulent; petioles (1.5-)2-5 cm; rachis (4-)5-13 cm; gland either sessile or shortly stipitate, up to 1.3 mm diam, and a second gland rarely present between the first pair of lfts; lfts 4-7(-8) pairs, of most larger lvs at least 5 pairs, less strongly graduated than in var. hirta, ovate- or lance-acuminate, the longest (3-)3.5-6.5(-8) x 0.8-2.2(-3.2) cm, (2.6-)3-6 times as long as wide; peduncles (5-)8-24 mm; racemes mostly 4-10-fld, the axis together with peduncle becoming 1-3 cm; fls of var. hirta; ovules 60-78; pod (12-) 15-23 x (0.25-)0.3-0.45 cm, simply arched outward, the valves minutely or remotely strigulose-puberulent, rarely glabrous.—Collections: 43.

    Washes, riverbeds, mesquite thickets, secondary brush-woodland, n.-ward often with Larrea and on the central plateau ascending into the arid grasslands, now commonest in degraded, ruderal or roadside habitats, mostly between 700 and 2100 m but occasional on the Gulf and Pacific coastal plains as low as 70 m, interruptedly widespread over interior Mexico from the n. slope of the Transverse Volcanic range n.-ward on the w. slope to n.-e. Sonora, on the e. slope to s. Tamaulipas and n.-w. Chihuahua, thence around the sources of the Gila river in s. Arizona and extreme s.-w. New Mexico; occasional, perhaps only adventive, further s. in Mexico, to Morelos and (disjunctly) the valley of Oaxaca.—Fl. VII-XI.

    The var. glaberrima was known to Bentham only in the form of Wright 1032 from northern Sonora, which he pronounced closely similar to the original C. leptocarpa from Rio de Janeiro. This is certainly true so far as habit, sparse strigulose pubescence and relatively many-flowered racemes are concerned, but var. glaberrima has since emerged as a certainly native, xeromorphic and largely extra-tropical derivative of S. hirsuta var. hirta, separable from the rest of its species by the generally small, slightly more numerous, thicker-textured, yellowish-green leaflets in which all venation but the midrib is immersed. In the Gila Basin and on the Mexican Plateau proper var. glaberrima is a well-marked entity, but in the moister hotter conditions of the Volcanic belt the foliage becomes more ample, the hairs a little longer, and the variety fades insensibly southward into var. hirta. Along the Zacatecas-Durango border near 2000 m altitude an extensive local population is distinguished by the presence of a second petiolar gland between the proximal pair of leaflets.