Zygia lathetica

  • Title

    Zygia lathetica

  • Author(s)

    Rupert C. Barneby

  • Scientific Name

    Zygia lathetica Barneby & J.W.Grimes

  • Description

    5. Zygia lathetica  Barneby & Grimes, sp. nov. Z. basijugam proxime affinem habitu, indumento, stipulis parvis enerviis, foliis pallide olivaceis et pseudo-racemis caulifloris paucicapitulatis simulans, at corolla longiori 14—19 (nec 9.5-14) mm, androecii 64-100 (nec 46-40)-meri filamentis 36-40 (nec 23-30) mm longis liliacinis (nec albis), et praecipue legumine subdimidio latiori 20-23 (nec 11-15) mm lato macrosemio, seminibus ±22 (nec 11-12) mm longis testa rugosa nitida (nec laevi) diversa.- ECUADOR. Napo: Parque Nacional Yasuní, Añangu, 0°30'S, 76°25'W, 12.VII.82 (fl), J. L Luteyn (with Balslev, Clemants & Boeke) 8663. — Holotypus, NY; isotypi, AAU, QCA, QCNE. — Ibid., 21.VI.1982 (fr.), SEF 8822; paratypi, AAU, NY. — Etymology: Gr. lathetikos, easily overlooked.

    Slender trees 6-15 m with trunk to ±1 dm dbh, closely resembling Z. basijuga in habit, indumentum, small stipules, pallidly olivaceous foliage, and cauliflory, but differing in longer corolla, in longer and more numerous, pink-lilac (not white) filaments, and particularly in a broader pod and larger seeds. Stipules appressed, triangular or lanceolate 0.7-2 x 0.5-1.7 mm, thin-textured, evenulose, tardily deciduous. Lf- formula v-viii/15-19; lf-stk of larger lvs 11-17 cm, the petiole reduced to the lf-pulvinus, the longer interpinnal segments ±2-3 cm; nectary between the very short first pair of pinnae cupular thick-rimmed 1.2-1.8 mm diam, those at 1-3 further pairs and between few distal lft-pairs progressively smaller; rachis of longer pinnae 7-12 cm, the longer interfoliolar segments 5-8.5 mm; lft-pulvinule almost 0, the blade sessile against rachis; lfts oblong or lance-oblong from obliquely truncate, postically auriculate base, deltately and mucronate at apex, falcately or shallowly sigmoidally incurved, the longer ones 15-26 x 5-8 mm, ±3-3.3 times as long as wide; venation of Z. basijuga. Primary axis of pseudoracemes ±1.5-3.5 cm; peduncles 5-18 mm, each subtended by a bract charged with a small button-shaped nectary; capitula 5-9-fld, the receptacle 1-2 mm; calyx including solid base campanulate 2-2.3 x 1.2-1.8 mm, the teeth 0.1-0.25 mm, the tube puberulent, the rim glabrescent; corolla reddish, tubular-funnelform 14-19 mm, moderately dilated at limb, puberulent overall, the often unequal lobes 1.5-3.2 mm; androecium 64—100-merous, 36-40 mm, the filaments lilac (? yellowish), the stemonozone ±1.5-2 mm, the tube 16-20 mm; ovary sessile linear 2-2.4 mm, at anthesis glabrous or microscopically papillate. Pods pendulous, in profile broad-linear contracted basally into a short neck, nearly straight, 15-37.5 x 2-2.8 cm, compressed but biconvex, when well fertilized 12-16-seeded, the stiffly leathery, brown, coarsely venulose, glabrous valves framed by dilated, very shallowly undulate sutures, the endocarp narrowly thickened between seeds but not septiferous, the seed-locules resinous; dehiscence through the ventral suture, the valves finally ex-planate; seeds (few seen) obliquely basipetal, in broad view bluntly trapeziform ±22 x 17 mm, compressed but plumply biconvex, the papery, dark brown, wrinkled but lustrous testa loosely investing the embryo, pleurogram 0; no endosperm.

    In the understory of primary rain forest, on low hill country around the W edge of the Amazon basin, within 4°15'N-1°S and 72°-77°W, in SE Colombia (Amazonas, Meta) and adj. Ecuador (Napo). — Map —Fl. V-VII.

    Zygia lathetica has been confused in herbaria with the related Z. basijuga but is distinguished by larger flowers, more numerous and longer stamens, and especially by the massive pod and seeds (see couplet no. 4 in key to species of sect. Zygiopsis for measurements).

    The form from the Araracuara in Colombia (J. H. Torres 3145, 2 sheets, fruit and cauliflower on one sheet, leaves on another, NY) may merit some taxonomic status. The leaves are indistinguishable from those on plants collected in Ecuador, but the pods differ. The pods from Ecuador have leathery, glabrous, and internally resinous valves, whereas the pod from the Araracuara has woody densely brown-pilosulous valves that, at least when fully mature, are not internally resinous. As we have seen very few collections with fully ripe pods, as the leaves of all are nearly exact copies, and as the flowers from the population on the Araracuara are unknown, we defer any decision until more material comes to hand.