Macrolobium rubrum R.S.Cowan

  • Authority

    Maguire, Bassett & Wurdack, John J. 1957. The Botany of the Guiana Highland -- Part II. Mem. New York Bot. Gard. 9 (3): 235-392.

  • Family

    Caesalpiniaceae

  • Scientific Name

    Macrolobium rubrum R.S.Cowan

  • Description

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    Latin Diagnosis - Arbusculae 0.2-2 m altae, ramulis minutissime puberulis; stipulae caducae. Folia glabra, unijugata, rigido-coriacea; petiolus 6.5-12 mm longus, 3 mm diametro, desuper compressus. Petioluli 1-3 mm longi, glabri. Foliola 7.5-15 cm longa, 3-6 cm lata, valde inaequilateralia, arcuata, elliptica, basis latere inferiore auriculato, superiore acuto ad subobtuso, ad apicem acuta et extremitate saepe obtusa; costa sulcata supra, infra saliens, venuli conspicui. Inflorescentiae 4-13 cm longae, terminales, axe minutissime puberulo, pedunculo 0-2 mm longo; bracteis caducis, triangularibus, 1.5 mm longis et latis, acutis, minutissime puberulis extus, intus glabris. Pedicelli 2-4 mm longi, minutissime puberuli; bracteolae 12-14 mm longae, 4 mm latae, oblanceolato-oblongae, obtusae, carnosae, glabrae. Hypanthium 3.5-4 mm longum, glabrum, stipite 1-1.5 mm longo, glabro. Sepala 4, aequalia, 10-11 mm longa, 3-3-5 mm lata, cucullata, oblanceolato-oblonga, ad apicem ciliolata. Petalorum lamina 7 mm longa, 5.5 mm lata, ovalis, glabra, unguiculo ca. 10 mm longo, glabro extus, intus pilosulo, late alato. Filamenta 18-20 mm longa, ad basim villosa. Stigma capitellatum; stylus ca. 14 mm longus, glaber, ovarium ca. 3 mm longum, 1 mm latum, oblongum, glabrum, gynophoro 3.5 mm longo, glabro. Fructus (immaturus) 8-11 cm longus, 3-4 cm latus, oblanceolatooblongus, ad suturam dorsualem anguste alatus, glaber.

  • Discussion

    TYPE: Bracts, petal, and stamens red; fruit green. Abundant in sabanita 1 km east of Maroa, elev. 125 m, Rio Guainia, Venezuela, April 16, 1953, Bassett Maguire & John ]. Wurdack 35684 (NY). Paratypes: VENEZUELA: Amazonas, Rio Guainia: frequent in Sabana El Venado on left bank of Cafio Pimichin above Pimichin, elev. 140 m, April 1953, Maguire & Wurdack 35620; frequent in sabanita 1 km east of Maroa, 130 m elev., Nov. 1953, Maguire, Wurdack & Bunting 36412.

    In the key in my revision, M. rubrum will run out quite near to M. punctatum, and they are rather closely related species. However, they are separable by several differences: (1) the new species has leaflets on which the costa is more or less sulcate on the upper surface; (2) its bracteoles are considerably larger; (3) its hypanthium is usually longer, and on a shorter stipe; and (4) the sepals and the petal-claw are markedly longer. In floral dimensions, the new species is nearer M. canaliculatum but the latter has the petal reflexed and it has rather differently shaped leaflets to separate it from M. rubrum.

    The specific epithet is chosen as being descriptive of the completely red flowers of this species. In ether taxa of the genus, various parts of the flower may be red or reddish but completely red flowers are unusual.