Abarema ferruginea

  • Title

    Abarema ferruginea

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Abarema ferruginea (Benth.) Pittier

  • Description

    2. Abarema ferruginea (Bentham) Pittier, 3rd Conf. Interam. Agric. Caracas 360. 1945. Pithecolobium ferrugineum Bentham, London J. Bot. 3: 216. 1844.-"British Guiana [but very likely on the Venezuelan slope of Mt Roraima], Schomburgk, n. 663 of 1843." — Holotypus, Rich. & Rob. Schomburgk 663 = 994, K!; isotypus, †B = F Neg. 1193; possible isotypus, U 38869!. — Feuilleea fulvescens (Bentham) O. Kuntze, Revis. Gen. Pl. 1: 185. 1891; non F. ferruginea (Guillemin & Perrotet) O. Kuntze, l. c.

    Pithecolobium ferrugineum sensu Bentham, 1875: 583.

    Arborescent shrubs attaining 8 m, the bark gray lenticellate, the stout, straight, rather distantly foliate hornotinous branches together with all lf- and inflorescence-axes densely pilosulous with golden-brown hairs to 0.1-0.3 mm, the thick-textured, sublustrous but sharply venulose lfts upwardly imbricate against the pinna-rachis, when dry brown above, pale brown beneath, puberulent along midrib on both faces, thinly microscopically ciliolate, the large, many-fld capitula arising singly in distal lf-axils on peduncles as long or commonly longer than the associated lf-stk; terminal meristem indeterminate. Stipules linear-lanceolate to -elliptic 4-7 x 0.75-1.5 mm, quickly deciduous from the expanding lf. Lf-formula iii—iv/8—11; lf-stks 5-7 cm, the petiole 1.2-2.0 cm, the longer interpinnal or immediately below pinna-pairs concave-patelliform to scutiform (2-)2.5-4 mm diam, livid becoming pallid in age, similar but much smaller ones on pinna-rachis at 1-2 furthest pairs of lfts; pinnae little graduated, 4—7 cm, the longer interfoliolar segments 5-8 mm; paraphyllidia not seen, but scars apparent on some specimens; lft-pulvinules wrinkled ±1.5 x 1 mm; lfts a little accrescent distally, inequilaterally rhombic-oblong-elliptic from rounded base, broadly obtuse, the longer ones 18-26 x 9-14 mm, 1.8-2.2 times as long as wide; venation of 3 nerves from pulvinule and thence pinnate, the moderately displaced, dorsally prominulous midrib incurved distally, the inner posterior primary nerve produced much short of midblade and the outer one very short, the 7-8 major and numerous intercalary secondary nerves brochidodrome within the plane, somewhat thickened margin, these in turn giving rise to a coarse reticulum of veinlets prominulous on both faces. Peduncles 5-13 cm; capitula ±45-60-fld, without filaments ±15 mm diam, the 5(randomly 6)-merous fls seemingly homomorphic (few whole capitula available for study) and sessile or almost so, the stout pedicel <1.5 mm; bracts decrescent upward, the lowest oblanceolate or trullate 5-7 x 2-2.5 mm, the upper ones spatulate shorter, all caducous; perianth densely appressed-silky overall, the indumentum of corolla golden, of calyx brown; calyx deeply campanulate 6.5-7.5 x 3.5-4 mm, the ovate teeth unequal, 2-3 mm; corolla 12-13 mm, the lobes ±3 x 2.2-2.5 mm; androecium 32-36-merous, ±3 cm, biseriate; ovary glabrous, truncately dilated at apex. Pods straight to ever so slightly falcate 5.5-6.6 cm long, 1.75-2.0 cm broad over seed-cavities, somewhat constricted between them, the lustrous dark-brown finely venulose valves framed by dilated sutures to 2.0 mm broad; dehiscence primarlily follicular, though perhaps eventually through both sutures, the valves not twisting or contorting, internally light red or orange-red over seed-cavities; seeds somewhat obliquely inserted on a broad, strap-shaped, twisted funicle, the seed broadly ovate elliptic, in profile 8-9.5 x 6.5-7.5 mm, with a finely incised, U-shaped pleurogram 4.25-5 x 2.5-3 mm, the seed-coat bicolored, the basal 1/4-13 white, the distal portion translucent, the embryo blue, but quickly fading to dark brown.

    On wooded slopes and ridges, 1100-1525 m, local in the Pakaraima Mts and on the Gran Sabana in SE corner of state of Bolívar, Venezuela and adjacent state of Roraima (Sa Sabang), Brazil, in lat. ±4°30'-5°30'N. — Fl. XII-I(-?), VII, the full season conjectural.

    Pithecolobium ferrugineum was described from a collection in flower, and this seems to be the only one seen by Bentham. In his monograph of Mimoseae (1875: 584) he nevertheless described the fruit as "legumen villosum, arcuatum v. circinatum, valvis 6-8 lin. latis contortis." We have seen only one fruit of A. ferruginea, and that fragmentary, but it is glabrous, as is the ovary of all known flowering specimens. The fruit described by Bentham, as noted by Sandwith in the protologue of P. fanshawei, was collected by Schomburgk and mistakenly associated with P. ferrugineum by Bentham. Sandwith thought it might belong to P. fanshawei or a close relative; we interpret the broken fragments of foliage as representing A. barbouriana var. arenaria.

    This species is closely related to A. floribunda and perhaps not specifically distinct. Abarema floribunda, primarily a plant of lower elevations, has leaves of thinner texture, longer leaf-stalks (and consequently proportionately shorter peduncles), and somewhat larger peripheral flowers (as described in the key to species). The petiolar nectaries of A. ferruginea are flat or shallowly concave, whereas those of typical A. floribunda are convex. However, a single collection of the upper Mazaruni basin in Guyana, described above as a variant of A. floribunda, with which it agrees in length of peduncles, in texture of foliage, and in size of flowers, has the flat nectaries of almost sympatric A. ferruginea, flowers only a trifle smaller, and comes from a habitat at 950 m. Further collecting may show that A. ferruginea is only an upland variant of the already highly variable A. floribunda, but this problem must be postponed for lack of critical material.