A New Species of Votomita (Melastomataceae) from Venezuela, with Thoughts on Ovule and Seed Number and Seed Size

Abstract

A new species of Votomita from southern Venezuela is described, illustrated, and distinguished from its relatives on the basis of fruiting material; certain useful floral characters can also be determined from the specimen. The new species illustrates a general condition in subfamily Memecyleae, i.e., a relatively large number of ovules is produced yet only one or a few large seeds are formed. Ovule and seed numbers are discussed, seed volumes are calculated for Mouriri and Votomita, and possible explanations for the differences are explored. Votomita ventuarensis Morley, sp. nov. TYPE: Venezuela. Terr. Fed. Amazonas: Dept. Atabapo, bosques medios y bajos inundables en el rio Ventuari-Macabana, 4?15'N, 66?20'W, 140 msnm, Sep. 1989, Luz Delgado 594 (holotype, MO; isotype, PORT). Figure 1. Arbor usque 15 m alta; pagina inferior costae mediae anguste 2-alata ad angulos, minute puberula; cryptae stomatatae unaquaeque cavitatibus 1-5; epidermes folii sine pigmento; hypodermis absens; stamina monadelpha; ovarium 4-loculare ovulis 22-25 axillaribus; semen unicum, globosum. Tree to 15 m high, glabrous except for the leaf midrib; young twigs rounded. Petioles 4.5-6 mm long; blades 7.9-12.4 cm long, 4.1-6 cm wide, ovate-elliptic to elliptic, acute at base, abruptly acuminate at the apex with an acuminum 0.7-1 cm long; midrib low-rounded to plane or slightly grooved adaxially when dry, prominent abaxially, flat and winged on the edges, the undermidrib minutely puberulent with hairs 20-40 pm long; lateral nerves when dry faintly visible or invisible adaxially, faintly visible abaxially. Midrib xylem tubular; stomatal crypts 30-36 per mm2 near the margin to 54 near the midrib, with (1-)2-5 cavities each, 50-60 /m high; adaxial epidermis of uniform thickness, 29-31 /tm thick including the cuticle, mostly one cell thick, occasionally two, mucilage walls none, the cytoplasm unpigmented and clear till stained, the inner walls straight and parallel with the outer ones; cuticle thin; abaxial epidermis also unpigmented; hypodermis none; foliar sclereids all terminal on the veinlets, irregularly stellate, often with an irregular horizontal central body 1-4 times as long as wide. Peduncles 1 per side at leafless nodes of twigs 3-4 mm thick below the leaf zone, 10.5-14 mm long with 2 internodes, the lower 0.5-1 mm long, the upper 10-13 mm, 1-flowered; bracts deciduous before fruit formation; pedicels 12-13 mm long in fruit; ovary locules 4, placentation axile, ovules 4-11 per placenta, 22-25 in all; fruits yellow to orange, ellipsoid, crowned with the calyx, 17-18 mm long including calyx by 12-14 mm diam. when dry, 20-21 mm long by 13-16 mm when boiled, the fruiting calyx 6.4-6.7 mm diam., 3-3.3 mm deep, the lobes low-triangular, 0.8-1.2 mm high, 4-5.2 mm wide; seed 1, spheroid, 9.79.9 mm high, 8.8-9.6 mm thick, with an irregularly elliptic raised area (function unknown) ca. 4 mm from the broken chalazal strand, the raised area 6 mm long, 4 mm wide, 0.5-1 mm high, with edges that overhang 0-0.5 mm; the raised area presumably includes the micropyle. Petal scars on the fruit rounded-triangular, 2.3-2.7 mm wide, 0.9-1.2 mm long; stamen scars 8, the filament scars broad, thin, and united, forming a continuous ring 3.2-3.7 mm in outside diam., 0.2-0.5 mm thick, the stamens thus monadelphous; thecae adaxial on the filaments and placed low so that their bases leave imprints 0.9-1.2 mm wide, 0.8-1.0 mm thick radially around the style base, the total stamen thickness at base 1.0-1.3 mm. Distribution. Known only from the type locality east of San Fernando de Atabapo, northwest of central Amazonas, Venezuela. Local name. Cometure tierra firmero. Although the type specimen bears only ripe fruits, the filament scars and anther imprints on the fruits yield useful floral information, and with careful dissection of the 1-seeded fruit (when boiled) all or most of the undeveloped ovules can be found and the nature of the placentation determined, in spite of the compaction and distortion that have taken place. The new species is unique in the genus in its unpigmented epidermises. Further distinctions of this plant from the other species follow, starting NovoN 9: 241-244. 1999. This content downloaded from 40.77.167.42 on Wed, 30 Nov 2016 05:02:53 UTC All use subject to http://about.jstor.org/terms