Macrosamanea pubiramea

Title

Macrosamanea pubiramea

Authors

Rupert C. Barneby

Scientific Name

Macrosamanea pubiramea (Steud.) Barneby & J.W.Grimes

Description

7. Macrosamanea pubiramea (Steudel) Barneby & Grimes, comb. nov. Inga pubiramea Steudel, Flora 26: 759. 1843. — Typus infra sub var. pubiramea indicatur.

Amply foliate, potentially arborescent and when crowded sarmentose or vinelike shrubs (1.5—)2— 6(-10) m tall, the old branches and trunks gray glabrate, the hornotinous ones together with axes of lvs and inflorescence sordidly pilosulous with short, incurved-ascending hairs, the brown-olivaceous lfts glabrous or microscopically ciliolate along midrib above, when mature stiffly chartaceous, the low-convex upper face smooth lustrous, veinless or almost so, the lower face a little paler, finely venulose, the well-furnished capitula of ascending, long and narrow, whitish or pinkish fls either axillary to coeval lvs or forming a very short terminal pseudoraceme immersed in foliage. Stipules erect-appressed, firm, lance-triangular 0.8-2.8 mm, at most faintly nerved dorsally, caducous. Lf-formula (ii—)iii—ix(—xiv)/(9—) 10—26(—31); lf-stks including coarsely wrinkled pulvinus (3—)5—21 cm, the true petiole commonly no longer than the first nectary, exceptionally to 6-15 mm, but always shorter than the interpinnal segments, these to 12-45(-55) mm; a sessile elliptic, shallowly concave, grossly callous-marginate nectary (2-)2.5-5 mm in long diameter situated immediately below first pair of pinnae, often impinging on or contiguous to lf-pulvinus, rarely distant from it, and similar but progressively smaller, mostly suborbicular ones between some distal pairs of pinnae and lfts; pinnae strongly decrescent proximally, less or not so distally, the short first pair ordinarily reflexed, the rachis of longer pairs (6—)7—15(—18) cm, their longer interfoliolar segments (2.5—)3—12(—17) mm; lfts except for few, gently decrescent proximal pairs and for the longer narrower distal pair all subequilong, the first pair either contiguous to the pinna-pulvinus or represented by minute subulate paraphyllidia, the blades linear-lanceolate to oblong or rhombic-oblong, mostly obtuse or obtuse and mucronulate, deltately acute when relatively narrow, at base cuneate on proximal and obtusangulate on distal side, the largest (10—) 12—30(—38) x (2-)2.5-17 mm, 2.1-5.2(-6) times as long as wide, the midrib of proportionately narrow lfts subcentric, straight or obscurely sigmoid, that of proportionately broad ones diagonal, one weak (and sometimes an outermost very short), narrowly intramarginal, posterior primary nerve produced to or beyond midblade, the costa pinnate, the secondary veins giving rise to weak sinuous tertiary venules, all venation usually immersed on upper face, always prominulous on the lower. Peduncles either solitary or 2-3 together, (l-)1.5-5.5(-9) cm, charged immediately below the capitulum with 1—2(—3) cycles of reflexed deltate bracts, each of these bearing on its adaxial (exposed) face a sessile, reddish or brownish, plane or crumpled, corneously margined nectary as wide as itself or wider; capitula (12—) 15— 25(-40)-fld, the ellipsoid or globose, alveolate receptacle 3-6.5 mm in greatest diameter; floral bracts fugacious, dry and brown before anthesis or possibly sometimes lacking, when present linear or linear- spatulate 0.7-2.5 mm; calyx and corolla faintly many-nerved externally, sordid- or pallid-puberulent overall, the corolla often a little more densely so, but sometimes both glabrescent in age; calyx either sessile or contracted at the often slightly bulbous base into a stout pedicel to 1.5 mm, overall 6.5-12 mm long, in lower 2/3 cylindric but expanded distally, the tube at middle 1.2-2(-2.4) mm diam, the ovate- apiculate or lanceolate teeth (l-)1.3-2.3 mm; corolla (16-)18-32(-34) mm, the slender tube very gradually dilated upward, the lance-ovate teeth 2-5(-6) mm; androecium ±80-106-merous (some interior filaments sterile), the staminal tube (at maturity of fl) usually exserted 2—10(—13) mm from corolla, but sometimes no longer or even a trifle shorter than it, the filaments white throughout or less often distally tinged with pink or carmine; ovary at anthesis glabrous; style exserted from the tassel of stamens, at tip either poriform or a little dilated and funnel-shaped, 0.2-0.3 mm diam; ovules 18-24. Pods 1-4 per capitulum, sessile, in profile oblong or broad-linear, usually a little decurved, (6-)8-14 x (2.2-)2.5-5.6 cm, broadly rounded at each end, apiculate, piano-compressed but early umbonate and finally tumescent over developing seeds, the brown, stiffly chartaceous valves framed by thickened sutures, thinly puberulent overall, transversely venulose; dehiscence through the ventral suture, the valves narrowly gaping to release seeds; seeds transverse on filiform funicle, imbricate by their margins and there becoming deformed by mutual pressure, plumply discoid and in broad profile elliptic-obovate 16-19 x 10-14 mm, the thinly papery, lustrously castaneous, fragile testa rugulose at middle of each face, carinate or incipiently winged around the periphery; cotyledons horny, cordate at base, the basal sinus either closed over or exposing the tip of the radicle.

Macrosamanea pubiramea is the most widely dispersed species of the genus and also the most variable in number of pinnae and in number and size of leaflets. As defined by the foregoing description it includes Bentham’s Pithecolobium adiantifolium var. multipinnum, P. longiflorum, and P. lindsaeifolium; modern collectors have not confirmed the habital differences that Bentham (1875: 590) thought might distinguish P. adiantifolium from the rest. Over much of the range of the species (Map 51) there is no difficulty in separating a var. pubiramea, with relatively narrow leaflets, from a var. lindsaeifolia, with broader ones. The var. pubiramea is the only form encountered in the Guianas or in Amazonian Brazil downstream from Manaus, whereas var. lindsaeifolia almost completely replaces it northwestward from the mouth of the Río Negro. We have from the banks of the lower Río Negro, however, examples of both varieties, and also of the related M. discolor, and some ambiguous forms that may represent introgression among the three. The riparian habitat is the same for all of them, so the opportunity for hybridization may easily arise. A few random records of one variety deep within the range of the other are perhaps based on individual variation too literally interpreted.

The name P. adiantifolium is illegitimate (see under M. discolor), and P. longiflorum is junior by three years to Inga pubiramea, which provides the unfamiliar, but unavoidable epithet in Macrosamanea.