Encephalartos imbricans, a new species from Uganda, is described, illustrated, and circumscribed in terms of other tropical African arborescent species. It is a large arborescent plant, with leaflets mostly strongly incubously overlapping. The strobili are green and glabrous; the megastrobilus is ovoid, shortly pedunculate, with the surfaces of the bullae wrinkled; the microstrobili emerge in succession, being narrowly ovoid, longpedunculate, with the surfaces of the bullae smooth. Encephalartos is widespread in the eastern parts of Africa, from the Eastern Cape Province of South Africa to southern Sudan, extending westward through equatorial Africa to Ghana and Nigeria (Goode, 1989: 244; Fig. 1). Nowhere is it common; it occurs mostly as relic populations, of which a considerable percentage must be considered to be in danger of extinction. The description of E. imbricans brings the number of described and recognized taxa to 57. Encephalartos imbricans Vorster, sp. nov. TYPE: Uganda. Near northern shore of Lake Victoria, Oct. 1994, P. Heibloem sub E Vorster 3034 (holotype, K). Figures 2-5. Planta magna arborescens. Foliola plerumque valde incuba, minime leviter falcata, dentibus in marginibus ambobus ad spationibus 2S50 mm et dentibus 34 confertis concentratis ad basin marginis superioris. Strobili virides, glabri, bullarum porcis mediolateralibus integris; megastrobili ovoidei, breve pedunculati, bullarum faciebus radialiter rugosis; microstrobili in successione emergentes, anguste ovoidei, longe pedunculati, bullarum faciebus laevigatis. Large arborescent, unbranched plant; suckering profusely from base. Stem up to 6 m long, prostrate after 1.5-2.0 m from base, 400-650 mm diam., covered with old leaf bases. Fronds numerous, spreading, straight, emerging fresh medium green and maturing to dark glossy green, about 2(-3.5) m long, leaflets gradually reduced to prickles toward proximal part of petiole to leave no prickle-free petiole; median leaflets orientated NOVON 5: 388-394. 1995. at angle of about 45° with rachis toward apex of frond, opposing leaflets are in the same plane as seen in cross section of leaf, very narrowly ovate and very slightly falcate, with teeth 25-50 mm apart on both margins and often 34 closely spaced teeth near base of upper margin, mostly strongly incubously overlapping, 200-250 mm long and up to 22 mm wide. Megastrobili 2-3, ovoid with apical sporophylls sterile, shortly pedunculate with exposed peduncle 3040 mm long, glaucous green, glabrous, about 300 mm long and 180 mm diam.; bullae of sporophylls moderately projecting, terminal facet centrally situated and about 1/3 the horizontal diameter of bulla, median facet differentiated in most sporophylls, ridges separating facets clearly differentiated and simple, terminal facet smooth but other facets radially rugose. Microstrobili 54, emerging and maturing in succession, each carried on a stout peduncle up to 300 mm long; strobili glaucous green, glabrous, about 300 mm long and 90 mm diam. at maturity; bullae of sporophylls moderately projected, slightly drooping, only terminal facet differentiated and about 1/3 the horizontal diameter of bulla, smooth. Seed covered with orange (not red) sarcotesta, about 45-50 mm long and 25-30 mm wide; with sarcotesta removed about 40 mm long and 18-24 mm wide. Variation. A concentration of 3 to 4 closely spaced teeth near the base of the upper margin is present in most (Foig. 2B), but not all (Fig. 3), leaflets. Likewise, the majority of plants have strongly overlapping leaflets; but through a quirk of fate the frond collected for the type specimen has wellspaced leaflets it probably developed in a situation where it was shaded by other plants and thus became etiolated. Phenology. During October the plants had fresh male and female cones, and seeds from the previous season were scattered about. A mature megastrobilus collected at this time disintegrated in mid-November, suggesting that the megastrobili take slightly more than a year to mature. Geographical distribution and habitat. Known This content downloaded from 157.55.39.177 on Wed, 16 Nov 2016 04:34:13 UTC All use subject to http://about.jstor.org/terms