Buchenavia

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Buchenavia

Description

Trees up to 55 m, taller ones with buttresses, not spiny; only 'combretaceous hairs' present. Leaves spirally arranged, usually clustered at branchlet tips, often with domatia in secondary vein-axils (pocket-shaped, except usually bowl-shaped in B. fanshawei); usually with petiolar glands. Inflorescences axillary lax to congested simple spikes, elongated or subcapitate, usually clustered at branchlet-ends; bracts very small and caducous. Flowers bisexual, actinomorphic, sessile, 5-merous; lower hypanthium extended into a distinct distal pedicel-like 'neck',upper hypanthium cupuliform, neck and upper hypanthium deciduous before fruiting; calyx lobes absent or scarcely developed; petals 0; stamens 10, slightly exserted, anthers adnate to filaments; disk densely pubescent; style free, usually 1-3 mm long, included to shortly exserted, glabrous. Fruits 5-ridged or ± terete, variably succulent pseudodrupe, radially symmetrical or rarely somewhat flattened, ridges sometimes very pronounced.

Distribution

Guianas: present New World: present Southern America:, Brazil South (Rio Grande do Sulpresent); Costa Rica (Costa Ricapresent); Cuba (Cubapresent)
A genus of 20 species, confined to the New World, extending from Costa Rica and Cuba southwards to Brazil (Rio Grande do Sul); 13 species occur in the Guianas.

Taxonomy

The genus is divided into 2 sections, both represented in the Guianas:
  • Buchenavia. Flowers at full anthesis congested into subcapitate spikes; rhachis up to 1 cm and usually much less, not or scarcely elongating in fruit. Buchenavia ochroprumna, B. parvifolia and B. tetraphylla.
  • Dolichostachys. Flowers at full anthesis in more or less elongated spikes; rhachis usually more than 1.5 cm, if less then considerably elongating in fruit. The other 10 species.

Wood

The sample of B. tetraphylla deviates from the other species studied in a number of characters: the presence of infrequent radial vessel multiples, the square/upright ray cells, the dark solid contents in the rays and parenchyma cells, and the bands of thin-walled fibres. Growth rings indistinct or absent.
Vessels diffuse, round to oval, predominantly solitary and in infrequent small radial multiples of 2(-3) cells, but up to 8 in B. tetraphylla; tangential diameter 90-170(-200) μm, often a few small vessels present, 3-6(-8) per mm², but up to 12 in B. tetraphylla. Perforations simple. Intervessel pits alternate, polygonal, 6-8 μm, vestured; vessel-ray pits similar to intervessel pits but half-bordered.
Rays uniseriate, consisting of procumbent body ray cells and 1 or 2 rows of square to upright marginal cells; cells square or nearly so in B. macrophylla, square and upright in B. tetraphylla; 5-11(-13) /mm.
Parenchyma apotracheal scantily diffuse; paratracheal vasicentric to aliform-confluent, often connected to narrow marginal bands; strands of 4-7 cells.
Prismatic to elongate crystals sometimes present, filling the ray or parenchyma cells. Solid contents present in axial and ray parenchyma of B. macrophylla. Small granular silica grains reported by van Vliet (1979) for B. acuminata and B. fanshawei.
Ground tissue fibres thin- to thick-walled, or very thick-walled, partly septate but frequently so in B. fanshawei, pits simple to minutely bordered, mainly on radial walls. In B. tetraphylla, some bands of thin-walled septate fibres alternate with the thick-walled, partly septate fibres.

Notes

There remain several taxonomic problems in the genus, in which there are few obvious diagnostic characters. Good fruiting material is usually sufficient for naming, but sterile material or collections with old fruits or with flowers often remain unnamed.