Combretum formosum G.Don

  • Authority

    Stace, C. A. & Alwan, A.-R A. 2010. Combretaceae. Fl. Neotrop. Monogr. 107: 1-369. (Published by NYBG Press)

  • Family

    Combretaceae

  • Scientific Name

    Combretum formosum G.Don

  • Type

    Type. Brazil. Rio de Janeiro, Morsan s.n. (herb. Lambert fide Don, BM, not traced; lectotype. G. here designated).

  • Synonyms

    Combretum argenteum Bertol., Combretum erianthum Benth.

  • Description

    Species Description - Woody liana in tall trees, with trunk to 30 cm diam., or shrub to 3 m; combretaceous hairs an peltate scales present. Leaves opposite, chartaceous, 2.3-14.5 × 1.2-6 cm, elliptic or oblong-elliptic to narrowly so, obtuse to acuminate at apex, cuneate rounded or subcordate at base, rufous-tomentose when very young but the pubescence soon wearing off and usually subglabrous when full-sized, moderately to rather densely yellowish- or golden-lepidote abaxially, sparsely or very sparsely so adaxially. Venation as in C. fruticosum. Petiole 0.3-1.2 cm, densely pubescent when very young but sparsely pubescent to subglabrous at maturity, moderately to densely golden-lepidote. Inflorescences unbranched, stout, in opposite pairs in leaf-axils, 6.5-15 cm, usually aggregated into terminal racemes to 36 cm, at the lower nodes in axils of normal leaves (usually fallen by fruiting time), at the upper nodes usually without or with much reduced subtending leaves, golden- to rufous-tomentose when young, the pubescence slowly wearing off but still strongly evident at fruiting and still obscuring scales, moderately to sparsely lepidote but many scales reduced in size. Flowers borne densely around rhachis but in nature all swept up to vertical position from more or less horizontal rhachis, with long exserted stamens forming bottle-brush syndrome, tetramerous, 12-14 mm, golden- to rufous-pubescent, the tomenturn totally obscuring scales which are all reduced size; lower hypanthium ca. 3.5 mm, with pedicel-like proximal region ca. 0.6 mm; upper hypanthium 8.5 10.5 mm, with narrowly infundibuliform proxima region 2.5-3.5 mm and usually rather poorly demarcated distal deeply cupuliform to infundibuliform region 3.5-4.5 × 4.5-5.5 mm excl, calyx lobes but the two regions scarcely distinguished; calyx lobes 2-3 mm, erect, acute; petals 4, 1.8-2.5 × 1.5-2.1 mm, usually falling just short of calyx lobes, broadly elliptic to orbicular, acute to shortly acuminate, without a basal claw, glabrous; stamens 8, far exserted, with filaments 18-21 mm; disk densely pubescent at margin with straight hairs, with distinct free margin to 1 mm, style 22-26 mm, exserted ca. as far as stamens, glabrous; ovules 6-7. Fruit 1.5-2.5 × 1.3-2.1 cm, very broadly elliptic to orbicular in side view, truncate to rounded or retuse at base, with very distinct narrow pseudostipe 0.2-0.4 cm, rounded to retuse and usually very shortly apiculate at apex, moderately pubescent especially on body and pseudostipe but sometimes all pubescence gone by mature fruiting, moderately to very sparsely lepidote but all scales reduced in size; wings 4, 0.4-0.8 cm wide. Scales as in C. fruticosum, but often much reduced in size and complexity where highly obscured by hairs. Reproductive biology. Little direct information, but probably most comments concerning flower color and pollination under C. fruticosum apply equally here. A specimen from Brazil: Rondonia (Ulisees & Coelho s.n.) is labeled as having aromatic yellowish green flowers, but scent is unlikely. In Central America flowering November to January; fruiting December to March. Flowering in May in Brazil.

  • Discussion

    Uses. None noted, but it would be a magnificent ornamental.

    Illustrations. Figs. 49d (trichome), 50g (fl), 51b (fr). Eichler (1867), fl, pl. 34 (as C. erianthum); Exell (1953), fl, p. 115 (as C. argenteum).

    Combretum formosum differs conspicuously from all other members of section Combretum in its dense golden tomentum (often dulling to rufous in dried material) on the inflorescences, flowers, and very young developing leaves. The epithet argenteum refers to the color of the upper leaf surface in the original material, a feature of the old leaves of many herbarium specimens of C. fruticosum and other members of section Combretum. The tomentum on the hypanthia of C. formosum conceals varying numbers of reduced peltate scales which are usually not visible with a hand lens, whereas the scales on the leaves are of the normal C. fruticosum type. In the latter species numerous normal-sized scales are always visible on the hypanthium between the hairs. Such specimens with rufous-pubescent hypanthia but with normal-sized scales clearly visible could be considered as intermediate between the two species, but they are variable in other characters and in my opinion fall under C. fruticosum. Examples are the type of C. benthamianum (Barclay s.n.) from Honduras, and 0rsted 3416 from Nicaragua; the latter has normal pollen full of contents. Combretum formosum also differs from most specimens of C. fruticosum in that there is a poorer demarcation between the proximal and distal regions of the upper hypanthium, but some specimens of the latter approach C. formosum very closely in this feature. Although separation largely rests on a single character, C. formosum does appear to constitute a taxon rather than an assemblage of specimens across the range of C. fruticosum that happen to possess tomentose flowers, because it is relatively constant in its other floral features. Nevertheless some fruiting specimens supposedly of C. formosum have lost all pubescence and are indistinguishable from C. fruticosum. It remains possible that C. formosum is only a chance mutation and that varietal rank under C. fruticosum might eventually prove to be the best option, but present evidence is equivocal.

    The application of the name Combretum formosum G. Don was for a long time uncertain in the absence of type material; it could equally refer to C. argenteum or to unusually densely pubescent C. fruticosum. Eichler (1867) did not see a type and was not sure to which species it belonged. Exell (1953) referred it to C. fruticosum, but his decision was probably largely based on the fact that he knew C. argenteum only from Central America, whereas C. formosum was collected in Rio de Janeiro. Don said that the type specimen of C. formosum was in herb. Lambert, which is in BM; however no such specimen can now be traced there. The specimen labeled C. formosum (by Müller-Argoviensis, after 1871, fide F. Jacquemoud, pers. comm.) in G collected by Morsan in Rio de Janeiro and dated 1830 (date of accession, written by De Candolle, fide F. Jacquemoud) does represent the same species as C. argenteum, and F. Jacquemoud (pers. comm., 2002) has informed me that it “is very likely to be a duplicate of the one seen by Don in herb. Lambert, but it is all but sure that it was also seen by Don." Hence it seems fairly certain that the Morsan specimen is authentic material of C. formosum, and likely to be a syntype. I have selected it as lectotype, but if that should prove too optimistic it would form a satisfactory neotype. Specimens that came directly from herb. Lambert to G-DC are “indicated on the labels by A. P. DC. himself (most of them were bought in 1842 by Delessert and given to DC.)” (fide F. Jacquemoud), but it is quite possible that the mysterious Mr. Morsan sent the sheet in question twelve years earlier.

  • Common Names

    peine de mico, papamiel, bejuco chupamiel, tombor

  • Distribution

    Humid subtropical or deciduous forests, dry or seasonally inundated terrain, and persisting as shrubs in matorral, pastures and rocky slopes, at 20-1000 m. Frequent on the western side of Central America from Guerrero, Mexico (ca. 17° N) to Nicaragua (ca. 11° N); and rare and very widely scattered in South America S to Rio de Janeiro, Brazil (ca. 23° S).

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