Tabebuia obscura (Bureau & K.Schum.) Sandwith
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Authority
Gentry, Alwyn H. 1992. Bignoniaceae--part II (Tribe Tecomeae). Fl. Neotrop. Monogr. 25: 1-370. (Published by NYBG Press)
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Family
Bignoniaceae
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Scientific Name
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Type
Type. Brazil. Amazonas: San Gabriel, Spruce 1979 (B*, lectotype, K; isotypes, F, NY, W).
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Synonyms
Tecoma obscura Bureau & K.Schum., Tabebuia subtilis var. schultesiana Sandwith, Tabebuia obscura var. schultesiana (Sandwith) Sandwith, Handroanthus obscurus (Bureau ex K.Schum.) Mattos
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Description
Species Description - Shrub or small tree to several meters tall, the branches subterete to subtetragonal, stellate pubescent when young. Leaves palmately 5-foliolate, the leaflets narrowly elliptic to oblong-elliptic, acute to acuminate, more or less rounded at base, the terminal leaflet to 15 cm long and 11 cm wide, the laterals smaller, entire, subcoriaceous, scattered lepidote above and especially below, above stellate-puberulous on the main nerves, below with stellate trichomes (and sometimes also with longer simple hairs) along the main nerves and sparsely over the surface (when young more densely stellate-tomentose over most of surface), drying olive-gray with conspicuous dark-drying glandular zones along the midvein below; petiolules to 4.5 cm long, the petiole to 13 cm long, reddish-stellate. Inflorescence a contracted few-15-flowered panicle, usually almost fasciculate, bracteate with subulate bracts 2-10 mm long, the pedicels tan, reddish-stellate, 4-8 mm long. Calyx campanulate, slightly 5-lobed, 8-14 mm long, 6-10 mm wide, conspicuously finely pubescent with thick-stellate trichomes, dark reddish, these less dense between the teeth, each tooth acute with a more densely pubescent striation descending from the apex; corolla yellow with reddish lines in the throat, tubular-infundibuliform, 5.5-8 cm long, 1.2-2 cm wide at mouth of tube, the tube 3.5-5.5 cm long, the lobes 1.5-2 cm long, glabrous outside except for some stellate trichomes on the lobes, the lobes minutely glandular-lepidote, not ciliate, the throat pleats sparsely puberulous with short papillate trichomes, adaxially glabrous, villous at level of stamen insertion; stamens didynamous, the thecae divaricate, 2 mm long; pistil ca. 3 cm long, the ovary linear, 2-3 mm long, 1 mm wide, sparsely lepidote, the surface smooth; disk cupular, ca. 1 mm long, 1.5-2 mm wide. Fruit a linear capsule, terete, 24-35 cm long, 1.3-1.7 cm wide, tapering apically, the valves thin, longitudinally irregularly and finely striate ridged, finely stellate-tomentose, with conspicuous scattered dark-drying glandular zones, each one with a plate-shaped gland in center; seeds thin, bialate, 0.6-1 cm long, 2.2-3.6 cm wide, the wings hyaline-membranaceous, sharply demarcated from seed body.
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Discussion
This species is extremely close to T. capitata, from which it cannot be reliably distinguished vegetatively. The calyces of T. obscura are generally longer and narrower than those of T. capitata with a redder indumentum and stronger tendency to slightly raised ribs. In addition, T. obscura tends to be a smaller tree and to have more persistently tomentose fruits and a stronger development of dark glandular areas in the lateral nerve axils of the leaflet undersurface. At least in Peru these two species seem ecologically distinct, with T. capitata occurring in clayey lateritic soils and T. obscura restricted to sandy soil. It seems probable that the rheophytic form with narrow leaflets that has been separated as var. schultesii is no more than an ecotypic variant.
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Common Names
palo de arco, pao d’arco, tahuari
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Objects
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Distribution
Northwestern Amazonia, mostly along the upper Rio Negro and tributaries, south to Amazonian Peru. Terra firme forests, mostly occurring on poor sandy soils; also on laja, especially along rivers; near sea level to 500 m.
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