Costus arabicus L.

  • Authority

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

  • Family

    Costaceae

  • Scientific Name

    Costus arabicus L.

  • Type

    Type. A drawing by Ehret of a plant cultivated in the Hortus Cliffortianus is designated as holotype. It is deposited in the library of Sir Joseph Banks (BM).

  • Synonyms

    Costus, Costus glabratus Sw., Costus niveo-purpureus Jacq., Costus sextus C.Roemer & Schult., Costus niveus G.Mey., Costus discolor Roscoe, Costus arrabidae Steud., Costus verschaffelt Lem., Costus glabratus var. niveo-purpureus (Jacq.) Sw. & Petersen, Costus pubescens S.Moore, Costus brasiliensis K.Schum., Costus pilgeri K.Schum., Costus validus Loes., Costus gracilis Loes., Costus pubescens S.Moore, Costus spiralis var. hirsutus Petersen, Costus ramosus Woodson, Costus spiralis var. hirsutus (Jacq.) Roscoe & Petersen, Costus pubescens f. fibrillosus Loes.

  • Description

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    Description - Plants 1-3 m tall often branched. Sheaths, ligules, petioles, and lower side of leaves glabrous, puberulous, or velutinous. Sheaths 5-15 mm in diam. Ligule truncate, 2-10 mm long. Petiole 2-7 mm long. Leaves narrowly ovate to narrowly obovate, the lowest ovate to obovate, cordate or rarely rounded at the base, shortly acuminate at the apex, 9-25 cm long, 3-10 cm wide, upper side glabrous. Inflorescence ovoid to fusiform, acute or obtuse, 3-10 cm long, elongating to 20 cm in fruit, 2.5-4.5 cm wide, to 6 cm in fruit, terminal on a leafy stem, rarely on a separate leafless shoot. Bracts green in the exposed part, red in the covered part, coriaceous, broadly ovate, acute or obtuse, 2.5-4.5 cm long, 2-3 cm wide, glabrous or rarely puberulous, callus 3-7 mm long. Bracts rarely appendaged. Bracteole pinkish red, 20-34 mm long, glabrous to sparsely puberulous. Calyx pinkish red or a little tinged with green, (10-) 12-22 (-27) mm long, glabrous to puberulous, lobes deltate, 2-6 mm long. Corolla niveous, 60-70 mm long, glabrous, tube 15-20 mm long, lobes narrowly elliptic to narrowly obovate, 40-50 mm long, 13-25 mm wide. Labellum snowy-white, broadly obovate when spread out, 50-70 mm long and wide, lateral lobes often tinged with purple, middle lobe recurved, blotched with yellow in the centre. Stamen snowy white, narrowly elliptic, 40-50 mm long, 10-15 mm wide, apex obtuse or irregularly lobed, tinged with purple, anther 6-12 mm long. Pollen size 118-150 µ. Exine 1.5-2 µ thick. Number of pores 6-11. Porus diam 18-38 µ (Florschütz & Maas 2574, 3158 from Surinam and Hort. Bot. Utrecht 68-200, also originating from Suriname). Ovary 3-12 mm long, glabrous to densely sericeous. Capsule ellipsoid, 10-18 mm long, glabrous to puberulous, seeds black. Chromosome number 2n = 18 (Maas, LBB 10886 from Suriname and Maas 3398 from Trinidad).

  • Discussion

    Costus arabicus is the most common representative of the genus in tropical South America and the Antilles. Its range extends throughout tropical South America except for the Andes Region and Central Brazil. It grows usually in moist sites eg along banks of streams, or in swamps; in Suriname it was often found in such habitats, only occasionally in the shaded interior of the forests. It also occurs at margins of savannas, in shady, moist places eg Norde & Oldenburger 740 (U), from the Sipaliwini savanna, Suriname, and Cuatrecsas 3583, 3772, 4318 from Los Llanos, Meta, Colombia.

    It is very easily identified in the field by its green inflorescence and snowy white flowers (often somewhat tinged with purple in the labellum and stamen). A peculiar feature is its often branched habit (cf C. ramosus), which is only rarely met with in the genus; the branches usually arise from the axils of the lowest bracts, but they also spring from leaf-axils. The leaf-base of C. arabicus is quite characteristic in being cordate, a feature which only rarely occurs in other species (see C. woodsonii). C. arabicus occurs in two forms, one with the inflorescence terminal on a leafy stem, the other with the inflorescence borne on a separate, leafless shoot; the second form is rare, it is represented by C. & F. Sastre 45 & 84 from Belém, Pará, Brazil; Black 57-19058 from Belém, Pará, Brazil; A. C. Smith 2869 from Shodikar Creek, Guyana.

    The indument of the lower side of the leaves is rather variable; in plants of the northern part of the area (Guianas and Antilles) the lower leaf-side usually is glabrous, but in the southern part of the area (Bolivia, Paraguay, and southeastern Brazil) it is puberulous to velutinous. This transition from glabrous to velutinous is so gradual, with all kinds of intergradations, that the character cannot be used for taxonomic distinction. The length of the calyx is also a variable feature; it slightly decreases from the northern to the southern part of the areal, from 16-22 mm in the Antilles to 10-12 mm in Paraguay. These two extremes are connected by a long and gradual series of transitions, without any sharp demarcation, the character is therefore not used for delimiting infraspecific taxa.

    Costus arabicus is closely related to C. guanaiensis and there is probably some introgression between the two species (see also under C. guanaiensis var macrostrobilus). Several plants were studied which had most characters of C. arabicus, but differed by their appendaged bracts, a character possibly due to introgression with C. guanaiensis. It was observed in the following specimens: Johnston 213 from Margarita I., Venezuela; Martius sn from Maué, Pará, Brazil; Pennell & Rusby 47 from Puerto Berrio, Santander, Colombia; Rodrigues 1628 from Rio Madeira, Amazonas, Brazil; Spane 14554 and *7857 from Hac. Clementina, Ecuador; Surian sn from Martinique; Pittier 10884 (G, GH, NY, US, VEN) from La Ceiba, Venezuela.

    Some Brazilian specimens were aberrant from C. arabicus by their ferrugineous-hirsute indument of all vegetative parts, and their cuneate leaf-base. They may well merit specific or varietal rank, but I prefer to wait for additional material before concluding so. The specimens are: Huber 7010 (MG), Hort. Bot. Mus. Goeldi, originating from Gurupay, Pará, Brazil; Pires 6596 (IAN), 7843 (IAN, U) from grounds of Instituto Agronomico do Norte, Belém, Pará, Brazil.

    Linnaeus (1753) described C. arabicus in the first edition of his Species Plantarum as follows:

    Costus arabicus Hort. Cliff. 2. Hort. Ups. 2.

    Mat. Med. 4. Roy. Lugd. 11.

    Costus arabicus Bauh. pin. 36. Mer. surin. 36. t. 36.

    Habitat in India utraque.

    The species was based on the description of a living plant in the Hortus of differt and originally described by Linnaeus (1737) in the Hortus Cliffortianus. This description, and a drawing made by Ehret of that specimen lead me to the conclusion that his living plant was from South America and identical with C. glabratus and C. niveus.

    Linnaeus had a broad concept of this species, for he cited as synonyms in his Hortus Cliffortianus: Tsjána-Kua, which is the present C. speciosus from Indo-Malaysia, furthermore Paco Caatinga and Merian 36. t. 36., from Brazil and Suriname respectively, both belonging to the present C. arabicus; the name C. arabicus has always been rejected as being a nomen confusum, but since Linnaeus only saw a living South American plant, as drawn by Ehret, there is no reason to do so. In his original description of Tsjána-Kua van Rheede tot Drakestijn (1692) remarked in a footnote that the roots of Tsjána-Kua showed some resemblance to those of Kostos arabikos of Dioscorides [see Matthioli (1572)]. The plant which Dioscorides described in his Greek Herbal, however, is not a Zingiberacea at all, but the composite Saussurea lappa or Saussurea hypoleuca [see Schumann (1904) p 399]. Linnaeus was quite mistaken when he named his Zingiberaceous species C. arabicus.

  • Distribution

    (Fig 24, 2). Antilles, tropical South America, especially the Guianas, the Amazon River Basin and South Brazil; in moist forests, on forested river banks, forest margins and in swamps, usually at sea-level.

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