Costus pulverulentus C.Presl

  • Authority

    Maas, Paulus J. M. 1972. Costoideae (Zingiberaceae). Fl. Neotrop. Monogr. 8: 1-140. (Published by NYBG Press)

  • Family

    Costaceae

  • Scientific Name

    Costus pulverulentus C.Presl

  • Type

    Type. Haenke sn (holotype, PR), locality unknown in Mexico.

  • Synonyms

    Costus ruber C.Wright ex Griseb., Costus laxus Petersen, Costus sanguineus Donn.Sm., Costus formosus C.V.Morton, Costus spiralis (Jacq.) Roscoe, Costus malortieanus

  • Description

    Description - Plants 0.5-2.5(-3.5) m tall. Sheaths, ligules, petioles, and lower side of leaves glabrous, puberulous, or villose. Sheaths 6-15 mm in diam. Ligule truncate or slightly two-lobed, 3-15 (-25) mm long. Petiole 2-10 mm long. Leaves narrowly elliptic to narrowly obovate, usually light brown when dry, cuneate to rounded, or rarely cordate at the base, shortly acuminate at the apex, (7-) 10-30 cm long, (3.5-)6-12 cm wide, upper side glabrous or rarely villose, costa densely strigulose. Inflorescence fusiform, usually sharply pointed at the apex, 3-7 cm long, 1.5-4.5 cm wide, enlarging to 20 cm long and 7 cm wide in fruit. Bracts red to orange-red (7.5 R 5/10 to 5.0 R 5/12) or occasionally greenish in the exposed part, covered part red (5.0 R 4/12), coriaceous, broadly ovate-triangular, acute, 2.5-4.5 cm long and wide, glabrous to puberulous, margins dilacerating into fibers, but often glabrescent with age, callus 5-10 mm long. Bracteole red, 18-23 mm long, glabrous to sparsely sericeous, margins usually dilacerating into fibers. Calyx reddish, 6-10 mm long, glabrous, margins often dilacerating into fibers, lobes deltate, 1-3 mm long. Corolla red (5.0 Y 5/12) to yellow, 50-70 mm long, glabrous, tube (10-) 15-20 mm long, lobes narrowly obovate, 40-50 mm long, 10-20 mm wide. Labellum red to yellow (2.5 R 8/10) oblong-obovate when spread out, 30-40 mm long and wide, lateral lobes rolled inwards and forming a slender tube of ca 8 mm in diam, upper margin irregularly 5-lobulate, middle lobule reflexed, narrowly triangular, 4-6 mm long, the other ones reflexed, deltate to triangular, 2-5 mm long. Stamen red (5.0 R 5/12) far exceeding the labellum, narrowly elliptic, 35-50 mm long, 4-10 mm wide, apex acute or obtuse, anther 4-8 mm long. Pollen size 104-138/11. Exine 2-3/1 thick. Porus diam 16-26 /u. Number of pores 5-8 (von Tiirckheim 7686 from Guatemala and Skutch 2775 from Costa Rica). Ovary 5-10 mm long, glabrous. Capsule ellipsoid, ca 15 mm long, glabrous, seeds black. Chromosome number 2n = 18 (Wessels Boer sn from Venezuela).

  • Discussion

    Costus pulverulenta appears to be most closely related to the Costa Rican C. barbatus and the Ecuadorian C. geothyrsus; it probably hybridizes with the latter (see under C. geothyrsus). Among the Central American material of C. pulverulenta I also found some specimens which showed some characters of C. pictus, eg, Liebmann 14723 (C, F, GH, US) from Huitamalco, Mexico, and Liebmann 14726 (C) from Jovo, Mexico; probably there is some introgression between these species, too (see also under C. pictus). Although a part of the herbarium material of C. pulverulenta presented problems because of introgression with C. geothyrsus and C. pictus, most plants could easily be identified by the following characters: inflorescence fusiform and pointed; margins of bracts mostly dilacerating into fibers; plants pale brown when dry; leaves often narrowly obovate, costa adaxially densely strigose.

    The species is common in Central and western South America; in the remaining part of tropical South America it is replaced by the vicarious species C. spiralis from which it differs by the pointed inflorescence, the strigulose costa, and the structure of the flowers, C. pulverulenta having a long stamen far exceeding the labellum, the stamen of C. spiralis, in contrast, being short and not exceeding the labellum.

    Costus pulverulenta is one of the most variable species, especially with respect to vegetative characters like indument and leaf-shape. The variation of both characters being rather continuous showing many transitional forms, they are not used for delimitating taxa at any level. This polymorphic species will have to be studied in the field with special attention to ecology and floral morphology.

  • Distribution

    (Fig 48, 8). Mexico, Central and western South America; in undergrowth of moist, dense forests, in clearings and along creeks, in plantations and wooded ravines, from sea-level to 1400 m.

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