Sclerosperma G.Mann & H.Wendl., Trans. Linn. Soc. London 24: 427 (1864)

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Diagnosis

Description

  • Short or acaulescent, clustering, unarmed, pleonanthic, monoecious palms. Stem if evident, creeping or erect, rather stout, closely ringed with leaf scars. Leaves reduplicate, bifid or divided, very large, deeply bifid in juveniles, ascending; sheath rather short, splitting opposite the petiole, margins fibrous; petiole long, slender, adaxially channelled, abaxially rounded; leaflets when present, composed of several very narrow folds, midribs prominent, marginal ribs next largest, blade adaxially dark, abaxially covered with a dense layer of amorphous white indumentum and with small scales along the veins, folds apically praemorse, margins minutely toothed, transverse veinlets not evident. Inflorescences interfoliar, concealed among the leaf bases and sometimes partially obscured by accumulated debris, spicate; peduncle very short, elliptic in cross-section, densely tomentose; prophyll rather short, strongly 2-keeled, becoming fibrous; peduncular bract longer than the prophyll, tubular, forming a fibrous net around the flowers, opening distally and inflorescence becoming partially exserted, 2 incomplete, pointed peduncular bracts borne laterally just below the flowers; rachis longer than the peduncle, but short, stout, bearing a few (ca. 12) triads of flowers at the base and numerous rows of staminate flowers distally, triads each subtended by a shallow pointed fibrous bract, the distal staminate flowers by small acute bracts; floral bracteoles present in triads, flat, ± rounded and partially united. Staminate flowers in triads ± pedicellate and asymmetrical, distal flowers sessile, symmetrical; sepals 3, distinct, imbricate basally, elongate, tapering, truncate apically or with a short central point; petals 3, distinct, valvate but tips flattened and buds truncate apically, thick; stamens 60–100, filaments very short, ± triangular, anthers elongate, basifixed, latrorse, connective prominent, apiculate; pistillode lacking. Pollen symmetric oblate-triangular in polar view, heteropolar; three operculate pores positioned subapically on the distal face; ectexine tectate, perforate, perforate-rugulate, rugulate or reticulate, aperture margins similar or slightly finer; infratectum columellate; longest axis 37–59 μm; post-meiotic tetrad tetrahedral [2/3]. Pistillate flowers larger than the staminate, broadly ovoid; sepals 3, connate in a 3-lobed, glabrous cupule or margins of 2 sepals distinct and imbricate, somewhat angled by mutual pressure; petals 3, distinct, asymmetrical, broadly imbricate with thick valvate tips; staminodes 6, very small, triangular or absent; gynoecium ovoid, unilocular, uniovulate, covered in thin brown scales, bearing a large, cap-like, 3-angled stigma; ovule ± pendulous, probably campylotropous. Fruit globose to obovoid, depressed apically around a short beak of stigmatic remains, purplish to black at maturity; epicarp thin, mesocarp thin, parenchymatous with silica(?) inclusions, endocarp bony, thick, irregularly and shallowly pitted externally, with basal pore region. Seed globose to obovoid, somewhat rough, hilum elongate, endosperm homogeneous; embryo basal. Germination remote-tubular; eophyll bifid. Cytology not studied. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)

Fossil record

  • Problems in understanding the morphology of the triporate pollen of this genus can be traced to a drawing of a dessicated pollen grain that is described as typical (Erdtman and Singh 1957). As a result, Tertiary records of protrudent triporate-fossil pollen, Trilatiporites, from India have often been wrongly associated with Sclerosperma (Harley and Baker 2001), for example by Bande and Ambwani (1982), Misra et al. (1996) and Srivastava (1987–8). One of the few accurate records is that of Médus (1975), who published illustrations of triporate pollen from the Bignona borehole (Miocene) of Senegal that are comparable with pollen of Sclerosperma. (J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008)

Bibliography

A. J. Dransfield & N. Uhl & C. Asmussen & W.J. Baker & M. Harley & C. Lewis, Genera Palmarum. The evolution and classification of palms. 2008
B. World Checklist of Arecaceae