Senna galeottiana

  • Title

    Senna galeottiana

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna galeottiana (M.Martens) H.S.Irwin & Barneby

  • Description

    145.  Senna galeottiana (Martens) Irwin & Barneby, comb. nov. Cassia galeottiana Martens, Bull. Acad. Roy. Bruxelles 10(2): 305 [=Enum. Synopt. Pl. Phanerog. ab H. Galeotti in reg. Mex. ... 9: 4]. 1843.—"Se trouve dans les plaines cactiferes de Tehuacan de las Granadas, de 5 a 6,000 pieds."—Holotypus, Galeotti 3227, collected VIII. 1840, BR! = BH Neg. 2499; isotypi, BR, K! = NY Neg. 1418.—Pterocassia galeottiana (Martens) Britton & Rose, N. Amer. Fl. 23(4): 243. 1930.

    Cassia galeottiana sensu Bentham, 1871, p. 547; Standley, 1922, p. 409.

    Crooked xeromorphic drought-deciduous shrubs and treelets 2-5 m, closely related to S. polyantha, essentially similar in individual flower and pod but the lvs shorter and simpler, the primary ones early deciduous, the rest crowded on short lateral branchlets or fasciculate on brachyblasts, the young growth pilosulous with fine spreading hairs up to 0.2-0.7 mm, the lfts pilosulous on both faces or beneath only, the racemes borne erratically in axils of primary lvs or on brachyblasts, sometimes on defoliate old wood, only rarely forming a panicle terminal to hornotinous long-shoots.

    Stipules heteromorphic, those of primary lvs (caducous, lacking from many spms) ovate or lance-acuminate 2.5-5 x 1.5-3 mm, the firm blades revolute, those of brachyblasts subulate 1-2 mm persistent.

    Primary lvs 2-4.5(-5) cm, those of brachyblasts mostly 1-2.5 cm, the two sorts not further described independently; petiole including wrinkled pulvinus (1.5-)2-5.5 mm, at middle (0.3-)0.4-0.8 mm diam, narrowly grooved ventrally; rachis (0.4-) 1-3.5 cm; gland 0; pulvinules 0.5-0.8(-1.2) mm; lfts (2-)3-8(-9, of some lvs at least 4) pairs, not or scarcely accrescent upward, the larger lfts obovate or oblong-obovate obtuse or emarginate 6-12 x 3-7 mm, 1.5-2.2 times as long as wide, membranous and revolute in flush of youth, firm plane in age, except for always dorsally prominulous midrib appearing veinless, or with 4-6 pairs of camptodrome secondary veins faintly raised on one or both faces.

    Racemes densely 10-45(-75)-fld, the axis including peduncle becoming (l-)1.5-6.5(-9) cm; bracts early reflexed, the firm, broadly lance- or ovate-deltate- acuminate blade (2-)2.5-6 x (1.6-) 1.8-4 mm, strongly revolute, persistent into, sometimes past anthesis, then deciduous; pedicels 10-34 mm; calyx, perianth, androecium and pistil of S. polyantha; ovules 10-15.

    Pod essentially that of S. polyantha but subsessile, the stipe at most 2 mm long, the body (excluding sutural wings) 5.5-9 x 1.3-1.9 cm, the locules 5.5-7 mm long, as wide as the cavity, the valves often reddish when fresh, turning dark brown or pale tan, dull, faintly venulose, dehiscent as in S. polyantha.—Collections: 20.

    Thorn forest and thin oakwoods on limestone and metamorphic bedrock, 1200-2000 m, known only from the Tehuacan Desert and vicinity in s.-e. Puebla and immediately adjoining Oaxaca.—Fl. III-VI, the fruits persisting into fall or winter.—Rompebota.

    The dispersal and what little is known of the ecology of S. galeottiana suggest that it is a recent derivative of S. polyantha, its abbreviated and proportionately simplified leaves, most of which are fasciculate or closely crowded on brachyblasts, being selectively adapted to the extremely severe conditions of the Tehuacan Desert. In summer 1906 C. A. Purpus made several collections of both species in the region of San Luis Tultitlanapa on the Puebla-Oaxaca border, but unfortunately recorded nothing of their habitats. It must be expected, nevertheless, that where their ranges coincide the two species are separated by altitude, microclimate or bedrock. We have some misgivings about the specific status of S. galeottiana, for in the detached flower and the pod it is essentially identical to S. polyantha. Its firm green reflexed and revolute floral bracts and similarly modified stipules are, with the diminished foliage and an inflorescence on the average less prolific and more lateral than terminally paniculate, the sum of differential characters perceptible in the herbarium.