Chloroleucon chacoënse

  • Title

    Chloroleucon chacoënse

  • Authors

    Rupert C. Barneby

  • Scientific Name

    Chloroleucon chacoense (Burk) Barneby & J.W.Grimes

  • Description

    2. Chloroleucon chacoënse (Burkart) Barneby & Grimes, comb. nov. Pithecellobium chacoense Burkart, Darwiniana 7: 513, fig. 2. 1947. — "ARGENTINA. Prov. de Salta: Jaquiasmé, F. Devoto y F. Rial Alberti, 22-XI-1938 [deflor., fr.]; Herb. Dir. Forestal Min. Agricultura n° 1661 ... PARAGUAY. Chaco central . . . 22° lat. S y 60°35/0, T. Rojas 8397, X.1938." — Holotypus, Hb. D.F.M.A. 1661, SI! (seen in photo, NY, kindly supplied by Pro- fesora N. Bacigalupo, V. 1989).

    Pithecellobium chacoënse  sensu Bemardi, 1984: 188, fig. 8.

    Macrophyllidious deciduous bushy treelets to 2-3.5m, with stiffly flexuous fuscous, sparingly lenti- cellate annotinous branchlets, either unarmed or armed at random nodes with stout supra-axillary thorns to ±1(-?) cm, glabrous throughout or the new branchlets and dorsal face of lfts puberulent, the foliage pale green subglaucescent concolorous, the capitula of creamy-white fls borne singly on short- shoots lateral to annotinous branchlets or exceptionally also in lf-axils of long-shoots: perulate buds (not evident on some young branchlets) ovoid or hemispherical 0.5-1 mm, castaneous glabrous. Stipules mostly obsolete, rarely subulate and to 2-4 mm, the blades thin-membranous caducous. Lf-formula i- ii/1—2(—3), commonly i/1-2; lf-stks 8-16(-24) mm, the petiole 8-20 mm, the interpinnal segment, if present, to 12 mm; a sessile elliptic nectary near middle, below middle, or rarely at apex of petiole 0.6-1.4 mm diam, similar smaller nectaries at insertion of lfts; rachis of pinnae 4-20 mm, the interfoliolar segment, if present, 4-10 mm; lfts when more than one pair accrescent distally, the further or only pair obliquely obovate from shallowly semicordate base, broadly obtuse, 15-29 x 12-22 mm, 1.2—1.6(—1.8) times as long as wide; venation of 4-5 primary nerves from the pulvinule, the almost straight midrib displaced to divide blade ±1:2, all primary nerves forked several times and giving rise to an open reticulum of venules prominulous on both faces of blade. Peduncles characteristically solitary at first node of brachyblasts, randomly also in lf-axils of long-shoots, 13-25 mm; capitula ±16—25-fld, without filaments 10-12 mm diam, the monomorphic fls sessile, glabrous except for minutely papillate-ciliolate corolla-lobes, the clavate receptacle not over 1.5 mm diam; bracts membranous minute, caducous long before anthesis of associated fl; perianth 5-, randomly 6-merous; calyx campanulate 2-2.4 x 1-1.1 mm, the depressed- deltate teeth 0.15-0.25 mm; corollas 5-6 mm, the tube striate-nerved, the ovate lobes variable in length, at most 1.7 mm, the blade concave ventrally; androecium 28-52-merous, ±12-13 mm long, the filaments united into a tube 5.5-6 mm, about as long as or distinctly exserted from corolla; ovary glabrous, conical at apex. Pods usually 1 per capitulum, narrowly oblong or oblong-elliptic from cuneate-attenuate or even short-stipitate base, 5.5-10.5 x 1.4—2(-2.3) cm, abruptly apiculate at apex, falcately decurved through scarcely ¼ circle, 5-9-seeded, the sutures 0.4-0.6 mm wide, the ventral one sometimes shallowly undulate but both often evenly curved, the stiffly papery, elaborately venulose glabrous valves fuscous dull; dehiscence apparently inert, through both sutures; seeds transverse on filiform funicle, not seen ripe.

    In open thorn forest, 350-900 m, apparently localized astride the Bolivia-Argentina-Paraguay boundaries in lat. 20°-23°S, 60°-64°W. — Map 38. — Fl. IX-XI; fr. III-IV(-?). — Palo barroso.

    Chloroleucon chacoense stands alone in its genus in greatly reduced leaf-formula and proportionately ample leaflets. Comparable leaf-reduction is seen in Zygia pithecolobioides (Hassler) Barneby & Grimes, ined. and Microlobius foetidus (Jacquin) Sousa.