Senna pallida var. foliolosa

  • Title

    Senna pallida var. foliolosa

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna pallida var. foliolosa (Benth.) H.S.Irwin & Barneby

  • Description

    177n. Senna pallida (Vahl) var. foliolosa (Bentham) Irwin & Barneby, stat. nov. Cassia foliolosa Bentham, Trans. Linn. Soc. London 27: 544. 1871.- "Guatemala, Skinner in herb. Lindley-Holotypus, Skinner 18, CGE! = NY Neg. 9691.-Peiranisia foliolosa (Bentham) Britton & Rose, N. Amer. Fl. 23(4): 265. 1930.

    Weak shrubs at anthesis 1-3 m with subterete annotinous and strongly sulcate, virgate or weakly plagiotropic annotinous branchlets, appearing glabrous but the stems and lf-stalks commonly minutely strigulose-pilosulous, the many small crowded lfts glabrous at least on both faces, the inflorescence axillary or corymbose and exserted.

    Stipules linear-attenuate 2-5.5 x 0.2-0.25 mm.

    Major lvs 5-14 cm; petiole (7-) 10-18 mm, 3-6 times as long as first segment of rachis; rachis 3.5-11.5 cm; gland between proximal pair stipitate 1.6-3 mm, the body 0.3-0.6 mm diam, rarely a smaller gland at second pair; petiolules 0.2-0.5 mm; lfts (12-) 15-31 pairs, not accrescent toward summit of rachis, narrowly lance-oblong, oblong, oblong-obovate or -elliptic obtuse or deltately acute 6-15 x 1.7-3.7 mm, 3-5 times as long as wide, the venation invisible above, the midrib prominulous beneath but the simple pinnate secondary venation of 4-7 pairs of nerves either immersed and faintly colored or altogether imperceptible.

    Inflorescence and flower of var. quiedondilla; style 1.5-2.5 mm.

    Pod (little known) like that of var. quiedondilla, the stipe 4-7 mm, the body 6.5-8.5 x 0.5-0.6 cm, the valves plane or nearly so; seeds 2.7-3.5 x 1.7-2 mm, the areole 1.1-1.2 x 0.5-0.7 mm.-Collections: 10.

    Quebradas and rocky hillsides in seasonally dry, often semideciduous brush- woodland, 900-1800 m, local in the highlands of s.-e. Guatemala (deptos. Zacapa, Chiquimula, Guatemala, Jalapa, Jutiapa and Sta. Rosa), to be expected in adjoining El Salvador.-Fl. X-II, perhaps also in summer.

    In the protologue of C. foliolosa, which was described from a single branchlet in young flower from an unrecorded locality in Guatemala, Bentham remarked that it had precisely the inflorescence of his C. biflora (=our S. pallida, p. max. p.) but leaflets much more numerous, smaller, and more simply veined, thereby suggesting some microphyllous form of S. multijuga. We now have matching material with fruit and seed which further emphasize the similarity to S. pallida var. quiedondilla, of a type unknown to Bentham, with essentially similar even though less numerous leaflets. Leaflets of holotypic Cassia foliolosa vary from 12 to 21 pairs, those of other, more modern collections 17 to 31 pairs; and the number rises in some var. quiedondilla to 17 pairs. The syndrome of diminished surface and augmented number of leaflets is a common modification of the senna leaf, the loss of photosynthetic area being compensated by reduplication, and we have no hesitation, in the absence of supporting differential characters, in reducing C. foliolosa to varietal status.