Swietenia humilis Zucc.

  • Authority

    Pennington, Terence D. 1981. Meliaceae. Fl. Neotrop. Monogr. 28: 1-359, 418-449, 459-470. (Published by NYBG Press)

  • Family

    Meliaceae

  • Scientific Name

    Swietenia humilis Zucc.

  • Type

    Type. Karwinski s.n., Mexico, Tehuantepec, fl, fr (holotype, M).

  • Synonyms

    Swietenia bijuga Preuss, Swietenia cirrhata S.F.Blake

  • Description

    Species Description - Young branches glabrous, slender with small roundish, brown lenticels; scales surrounding buds prominent, dark brown, acute. Leaves clustered at ends of branchlets, usually paripinnate rarely imparipinnate, sometimes with an abortive terminal leaflet, (12-)14-22(-30) cm long; rhachis glabrous, pulvinus swollen. Leaflets opposite or subopposite, sessile or subsessile, (2-)3-6(-7) pairs, usually ovate to elliptic-ovate sometimes ovate-lanceolate, apex caudate or long acuminate, extended into a slender filiform thread, base rounded or acute, slightly asymmetric, chartaceous, waxy, sometimes slightly glaucous beneath, (4.5-)7-9(-14) cm long, (1.75-)2.5-4.5 cm broad, upper and lower surfaces glabrous; venation reticulate; secondary venation raised and prominent on both surfaces. Flowers unisexual, but 6 and 9 flowers very similar; inflorescence usually axillary sometimes subterminal, (4-)8-12(-18) cm long, erect or spreading, much shorter than leaves, terminal thyrses often densely clustered, glabrous. Flowers sessile, subsessile, or with pedicels to 2 mm long, glabrous. Calyx 5-lobed, lobes obtuse, deltate to suborbicular, 0.5-1 mm long, glabrous, margin ciliolate. Petals 5, free, slightly contorted in bud, (5.5-)6.5-7.5 mm long, 2.5-3 mm broad, lingulate to obovate, glabrous, margin ciliolate. Staminal tube cylindrical or urceolate, slightly constricted at throat, (3-)3.5-4.5(-5.5) mm long, terminated by 10 short acuminate or narrowly deltate appendages, glabrous inside and out; anthers or antherodes 10, sessile ± contained within mouth of tube. Nectary annular or patelliform, margin crenulate or ribbed, glabrous. Ovary in 2 flowers globose (4-)5-locular, with (10-) 12-14(-16) ovules, glabrous; style very short, 1-1.5 mm long; style-head discoid, glandular with 4-5 stigmatic lobes. Pistillode in 6 flowers more slender, narrowly cylindrical with well-developed loculi but rudimentary ovules; style 2-3 mm long; style-head thin. Capsule erect, ovoid sometimes elongate-ovoid with a short umbo, pale greyish-brown, smooth or indistinctly pitted, 8-16(-20) cm long, 10-12 cm diam., (4-)5-valved, outer valves very woody, 5-7 mm thick, inner valves much thinner, mottled pale brown and white. Seeds pale straw-brown, 6-8(-9) cm long including wing. Embryo with cotyledons thin. Field characters. A small to medium-sized deciduous tree 15-20 m tall (specimens are rarely seen larger than this). Bole short, often crooked, unbuttressed, from 30-50 cm diameter, with dark-grey or brownish-black, longitudinally fissured bark; in older specimens rough and flaking. Old leaflets tend to lose their filiform apices due to wind and other damage and may then resemble those of S. macrophylla in shape. Flowering occurs in April and May and the fruit takes almost a year to mature. The white flowers are faintly but sweetly scented and are visited by bees. The large fruits standing erect above the foliage make the tree easily recognizable from a distance. This and the other two species exude a colourless gum from the trunk and branches. The bark and seeds possess a stringent alkaloid, reputed to be very poisonous.

  • Discussion

    Distribution and Ecology: Fairly common in tropical dry deciduous forest and savanna, in rough scrub, on rocky hillsides and in cultivated fields from 0-1200 m alt. Confined to the narrow dry coastal zone on the Pacific slope of Mexico from Sinaloa and Durango to Chiapas, throughout Central America to Guanacaste Province in northern Costa Rica. In Guatemala it occurs along the Motagua valley, almost reaching the Atlantic coast. Specimens collected in northern Honduras (Stead & Styles 261) and others are however almost certainly from planted trees. In Central America trees are most often seen as scattered and isolated individuals, preserved in cultivated fields and pastures. It is sometimes planted in hedges along roadsides and near homesteads. The species is of little commercial importance but the heavy timber is used in local carpentry. Provenance trials to test growth performance and wood quality are being conducted in Puerto Rico and in St. Croix (Geary et al., 1973). It is thought to hybridize with the other two species (Whitmore & Hinojosa, 1977). Swietenia humilis has recently been listed as an endangered species in need of conservation but this is felt by me to be unnecessary. (See 'Convention on International Trade in Endangered Species of Wild Fauna & Flora.' Special Supplement to IUCN Bulletin 4(3): 12 (1973).)

  • Common Names

    Dry zone mahogany, Pacific coast mahogany, caoba, Cóbano, Zapatón, Coabilla, gateado, Venadillo, zopilote

  • Distribution

    Mexico North America| Chiapas Mexico North America| Oaxaca Mexico North America| Guerrero Mexico North America| Morelos Mexico North America| México Mexico North America| Michoacán Mexico North America| Colima Mexico North America| Jalisco Mexico North America| Nayarit Mexico North America| Sinaloa Mexico North America| Durango Mexico North America| Guatemala Central America| Chiquimula Guatemala Central America| Retalhuleu Guatemala Central America| Zacapa Guatemala Central America| Huehuetenango Guatemala Central America| Honduras Central America| Choluteca Honduras Central America| Comayagua Honduras Central America| El Salvador Central America| San Vicente El Salvador Central America| San Salvador El Salvador Central America| Nicaragua Central America| Chontales Nicaragua Central America| Granada Nicaragua Central America| Managua Nicaragua Central America| Chinandega Nicaragua Central America| Nueva Segovia Nicaragua Central America| Costa Rica South America| Guanacaste Costa Rica Central America|