Chamaecrista serpens var. grandiflora

  • Title

    Chamaecrista serpens var. grandiflora

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Chamaecrista serpens var. grandiflora (Benth.) H.S.Irwin & Barneby

  • Description

    26b. Chamaecrista serpens (Linnaeus) Greene var. grandiflora (Bentham) Irwin & Barneby, comb. nov. Cassia serpens Linnaeus var. grandiflora Bentham in Martius, Fl. Bras. 15(2): 163. 1870.—". . . loco haud indicato Brasiliae: Weddell."—Lectoholotypus, Weddell 2286, from "rives de l’Araguay," P! presumed isotypi, Weddell s.n., G(3 sheets)!

    Cassia tenella Humboldt, Bonpland & Kunth, Nov. Gen. & Sp. 6(folio): 365. 1824.—"Crescit in ripa fluminis Orinoci, prope San Borja [in present Edo. Bolívar at 6°N lat.]"—Holotypus, labelled "n. 1182. San Borja Orinocensium," P-HBK! isotypi, P (hb. Bonpland.) = F Neg. 39839; B (hb. Willd. 7954)! Chamaecrista tenella (Humboldt, Bonpland & Kunth) Pittier, Cat. Fl. Venezol. 375. 1945.

    Habit, stature, foliage, pod of var. serpens, but flower larger, the cucullus (8—)9— 13(— 16) mm, the longer anthers up to 5-8 mm, the style (4—)5-6.5(-7) mm — Collections: 41.

    River banks, sandy floodplains, savanna (n.-ward) and campo (s.-ward), mostly below 600 m, known from 3 widely separated areas in S. America: banks of the Orinoco about the common boundaries of Apure, Amazonas, and Bolívar, Venezuela (to be expected in n.-e. Vichada, Colombia); Araguaia and Tocantins valleys in Pará and centr. Goiás, Brazil; middle and lower Paraguay and Paraná valleys in s.-w. Mato Grosso, Brazil, s.-centr. Paraguay and adjoining Argentina (Formosa; about the Misiones-Corrientes boundary); ?n.-centr. Bolivia (Mamore valley; cf. discussion infra).—Fl. at low latitudes nearly throughout the year, in Paraguay and Argentina mostly X-III, sometimes later.

    The three disjunct major populations which we refer to var. grandiflora are essentially alike in corolla-size, and differ only minutely in other characters. The plants of the Orinoco valley (C. tenella H.B.K.) tend to have, at maturity, very long stems, up to 5—10 dm, and relatively long petioles (2.5-4 mm) incurved- puberulent but lacking setae. In the context of copious material now available from the banks of the middle Orinoco the typus of C. tenella is peculiar only for its diminutive stature, the stems about 12 cm long from a knotty root-crown. It is evidently a depauperate individual, and led Bentham (1871, p. 571) to maintain the species in his ser. Paucijugae, next to C. schlimii, artificially separated from its real affinity within ser. Prostratae. The short-stipitate glands, now known to occur in typical C. serpens, may well have exerted an influence on the misinterpretation. The plants of Argentina and Paraguay are more compact, with stems 1-4 dm and short petioles (1.2-2.5, rarely 3 mm) setose as var. serpens. The two known collections from Goiás are intermediate in stature and petiole-length. North of Capricorn the leaflets are uniformly glabrous; in Argentina and Paraguay either glabrous or thinly setose, the latter prevailing in Argentina and the former around Asunción. A fragmentary specimen (O. Braun 2, NY) from the lower Mamore valley in dept. Beni, n.-centr. Bolivia, appears to represent a broad-leaflet form of var. grandiflora but lacks expanded flowers or fruits and is inadequate for analysis.

    The discontinuous range of var. grandiflora lies almost within that of var. serpens but they appear nowhere to overlap, the former indeed fitting neatly into gaps in the dispersal pattern of the latter. Perhaps var. grandiflora consists not of a phylogenetically pure strain but is a composite of parallel variants, at present morphologically inseparable, that have arisen independently from var. serpens and replace it locally.