Zygia latifolia

Title

Zygia latifolia

Author(s)

Rupert C. Barneby

Scientific Name

Zygia latifolia (L.) Fawc. & Rendle

Description

48. Zygia latifolia (Linnaeus) Fawcett & Rendle, Fl. Jamaica 4: 150. 1920. — Typus infra sub var, latifolia indicatur.

Macrophyllidious, cauliflorous, arborescent shrubs and slender trees, some precociously flowering at 2-4 m but mostly 4—15 m, exceptionally attaining 20 m, with trunk exceptionally to 3 dm dbh, the defoliate branches pallid smooth, the young stems and lf-axes either glabrous or thinly to densely gray- or sordid-pilosulous with hairs <0.6 mm, the ample papery lfts glabrous except for sometimes puberulent nerves of hypophyllum, the inflorescence composed of either sessile or shortly pedunculate capitula or short (but sometimes loose) spikes of either white, ochroleucous or pink, commonly pink-, rarely white-stamened fls, each unit of inflorescence arising singly from defoliate knots of trunk, branches, or both, well below current foliage, never assembled into pseudoracemes, but sometimes fasciculate. Stipules triangular-ovate, deltate, or lanceolate, 1—8(—10) mm, either deciduous or persistent through one season (exceptionally longer), in texture either thickened and externally nerveless, or thinner and prominently striate, when persistent sometimes becoming papery and blanched, in many specimens forming a loose tuft of scales at tip of current year’s branchlets. Lf-formula i/½-3½(-4½), the lfts most commonly either 3-5 or exactly 3 or 5 per pinna, the odd posterior one usually very small and sometimes lacking; petioles 2.5-10 x 1.4—3  mm, bearing at tip a sessile, subcircular or obtusely rhombic, plane or shallowly cupular nectary (0.8-)l-3.2 mm diam; rachis of pinnae 2.5-13 cm, the further interpinnal segments 1.5-8 cm, the first lft(s) usually <1 cm distant from pinna-pulvinus; pulvinule of lfts 2-5 mm; lfts accrescent distally, often strongly so, the blades narrowly to broadly elliptic or ovate-elliptic from inequilaterally cuneate base, shortly, bluntly or subacutely acuminate, the distal pair (4-)4.5-18(-20) x (1.4—) 1.7-7(-8.5) cm, mostly 2-3.3 (rarely -4.2) times as long as wide; venation asymmetrically pinnate, the proximal 1-3 (-4) secondary nerves on posterior side of midrib, usually in all lfts but always in the distal pair of lfts, at once longer and stronger than the rest, one or more of them produced well beyond midblade, the tertiary venulation weak. Peduncles mostly 0-3 mm, rarely to 12-20 mm; fls (3-)5-25, the receptacle commonly 1-4.5(-5.5) mm, rarely in Atlantic SE Brazil to 9.5 mm; bracts triangular acute 0.4—1.1 mm, persistent; perianth commonly strigulose on calyx-teeth and corolla-lobes but otherwise glabrous, sometimes glabrous except for microscopically ciliolate calyx or corolla-lobes, but in var. lasiopus puberulent or hispidulous overall with erect, ascending, or subappressed hairs <0.4 mm; calyx shallowly to deeply campanulate (0.3-)0.4-2.5(-3.3) x 1-1.3 mm, the tube striate, sometimes oblique at orifice, the low-deltate, sometimes scarcely perceptible teeth 0.1-0.6 mm; corolla either pink or white, commonly 4.5-8 mm, exceptionally only 3.5 mm or attaining 9(-10) mm, the striately nerved tube subcylindric to distally dilated, near orifice 0.7-2.6 mm diam, the ovate nerveless lobes ascending; androecium (18-)20- 38(-40)-merous, 14—30 mm, the usually white tube 6.5-14 mm, exserted 1-7 mm, the tassel rarely white also, usually pink or crimson distally; intrastaminal disc 0.3-0.7 mm; ovary at anthesis either glabrous or puberulent. Pods subsessile, linear or broad-linear in profile, straight or more often gently decurved, when well fertilized (6-)8-18 cm long, (0.8-)0.9-33 mm wide, ±8-14-seeded, at first planocompressed but becoming low-biconvex when distended by ripe seeds, the valves leathery, without pithy-ligneous mesocarp and <1 mm thick in section, densely minutely tomentulose overall to glabrescent (but always puberulent at least near the base, or along the sutures, or both), the sutures straight or very shallowly pinched between seeds; dehiscence of the genus; seeds uniseriate, contiguous or spaced along the cavity but not imbricate or mutually distorted, in broad profile round or bluntly rhombic, (8—)9—15(—18) mm diam, plumply discoid, the papery testa dull brown, pleurogram 0.

The concept of Z. latifolia implicit in the foregoing description is materially wider than any proposed hitherto. It embraces not only the original Jamaican Pithecellobium latifolium but also P. glabratum.

Martius and P. lasiopus, which Bentham (1876) interpreted as glabrate and pubescent phases of P cauliflorum, but also the historic nucleus of the latter, and the forms segregated as P. sanguineum Bentham, P. stipulare Bentham, and P. huberi Ducke. The material now available for comparative study shows that the supposed discontinuities among these taxa were illusory, reflections of a randomly assembled sampling. As redefined here, Z. latifolia is characterized by emphatically inequilateral secondary venation of the leaflets combined with pods of stiffly chartaceous or leathery, but not pithy-ligneous texture. Zygia cataractae, which has or can have essentially similar fruits, differs principally in equilaterally pinnate secondary venation of leaflets. The closely related Z. inaequalis has an often (but neither absolutely nor consistently) larger calyx coinciding with relatively numerous leaflets and less inequilateral venation, but it can be most surely separated by the tough, rigid valves of the pod.

Zygia latifolia, cataractae, and inaequalis are widely sympatric, are adapted to similar riparian habitats, and have very similar flowers; specimens of ambiguous identity are not rare in herbaria, and it is suspected that some of these may be of hybrid origin.

Characters employed in the past to define segregates of Z. latifolia are: (a) pubescence, especially of leaf-axes and perianth; (b) texture and persistence of stipules; (c) number of leaflets per pinna; (d) size of leaflets; (e) extension or contraction of the peduncle and the floral axis of inflorescence-units; (f) absolute and relative lengths of calyx and corolla; and (g) length and consequent exsertion of the androecial tube. Repeated attempts to sort the herbarium material into categories compatible with plausible dispersal patterns have met with small success. The lack of discontinuities in the variation of each character and the independent variation of most have led ineluctably to the comprehensive notion of Z. latifolia adopted here.