Mapania imeriensis (T.Koyama) R.Gross
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Authority
Maguire, Bassett. 1967. The botany of the Guayana Highland--Part VII. Mem. New York Bot. Gard. 17: 1-439.
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Family
Cyperaceae
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Scientific Name
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Description
Species Description - Tufted from short erect rhizome. Leaves basal and the uppermost one on the culm, conspicuously petiolate, 30-100 cm long; blades linear-oblong to narrowly lanceolate, 2-3 cm wide, unicostate, subcoriaeeous, gradually attenuate above to linear caudate apex, attenuate below to petiole 3-5 cm long, the margins smooth for most of length, serrulate-scabrous toward apex; sheaths 10-15 cm long, dilated below, yellow-brownish, the margins membranous dark brown; cauline leaves without petiolate portion, the sheath 5-7 cm long. Basal sheaths bladeless, 6-10 cm long, yellow-brown with purple-brown membranous margins. Culms central, taller than leaves, 30-100 cm tall, 2.5-3 mm thick below the middle, distinctly and acutely 3-angled, 1-leaved at the middle or below the inflorescence, the angles smoothish except immediately below the inflorescence. Inflorescence corymbose, sometimes slightly racemose with elongated axis, up to 6 cm long, 9 cm in diam, with 6-22 glomerules of spikes; bracts 2-3 leaf-like, the rest setaceous, scarcely sheathing; blades up to 20 cm long, 7-20 mm wide, attenuate from above the base to a long linear caudate apex, the margins serrulate-scabrous for most length; axis 2-3 cm long, hispid-scabrous on angles, densely hispid on sides with brown adpressed hairs; primary rays arising from ocreate prophyll, 1.5-4 cm long, spreading, terminated by 1 to 3 glomerules, secondary rays if present up to 1 cm long; prophyll ca 5 mm long, bicostatc, the mouth oblique; glomerules spherical, 7-12 mm diam, sometimes slightly lobed, rust-brown at maturity, with many spikes, each spike consisting of 7-10 spikelets, 4-5 mm long. Scales subtending spikelet ovate-elliptic, 2.5-2.75 mm long, 1-1.25 mm wide, shallowly navicular, chartaceous, brown, glabrous, abruptly acute at apex, ciliolate on upper margins; 2 lateral squamellae oblong, 2.25 mm long, 0.8 mm wide, strongly folded, hyaline, blunt at apex, ciliolate on upper margins, the keel distinctly spinulose above the middle, usually holding a stamen; 2 inner squamellae dorsiventral, linear or lanceolate, 2.5-3 mm long, hyaline, generally empty. Fructifications ovoid to lance-ovoid often ellipsoid-ovoid, 2-3.5 mm long, nearly 1 mm wide, biconvex, the basal part containing achene ca 1 mm long, brown, the spongy portion cream-colored, spotted with tannin-co’ored lineolae, the stigmas 2cleft almost to the base of style, 1-1.25 mm long.
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Discussion
Hypolytrum imeriense R. Gross, Repert. Sp. Nov. 50: 210. 1941. Hypolytrum sandwithii Gilly, Bull. Torrey Club 76: 291. 1949. Syn. nov
Type. Western foothills of Serra Imeri, near Salto de Hua, alt 800 m, near Brazilian-Venezuelan Boundary (Venezuela), E. G. Holt & E. R. Blake 509 (US).
Gilly apparently overlooked Hypolytrum imenense when he described this species as H. sandwithii. The fructifications of Mapania imeriensis are variable especially in the length of the spongy portion. The individuals called H. imenense and H. sandwithii represent two extremes in a continuous variation range of the fructification length, which tends from 2.5 mm to 4.5 mm excluding the stigmas.
Three species of South American Mapania, here treated as M. tepuiana, M. imeriensis, and M. condensata, stand distinct from the rest of the members of the genus by their fructifications, which have a long-extended spongy portion over the base containing an achene. Because of this peculiar feature Gilly claimed the taxonomic affinity of his Hypolytrum sandwithii ( = Mapania imeriensis) to H. strictum, of which the fructifications also have a well developed spongy portion over the base. This view, however, merely shows that the spongy fructifications of this type may occur in both genera.
The valid differences between Hypolytrum and Mapania consist in the leaf blades, which are tri-costate vs uni-costate, and the number of squamellae in a single spikelet. In Hypolytrum a spikelet has two lateral squamellae only, while a spikelet in Mapania always bears 4 to 6 squamellae. The spikelets of the three species mentioned above consist of 4 squamellae, of which the two lower ones are lateral and folded with spinulose keel the other two being dorsiventral, an arrangement typical of that of digynous spikelets in Mapania. The leaf blades of the three species are conspicuously uni-costate making no difference from other species of Mapania.
The presence of elongated rays in both M. tepuiana and M. imeriensis might have been the basis for the original authors to place these species in the genus Hypolytrum. Although the presence of such elongated rays seems to be confined to Hypolytrnum as far as the South American Gyperaceae are concerned, it does not warrant generic separation between Hypolytrum and Mapania in the Old World species since a number of Old World Mapanias have rayed inflorescence as well as those of Hypolytrum. The transfer of the three species from Hypolytrum to Mapania is thus properly justified.
Gillys original description of Hypolytrum sandwithii involves a considerable inaccuracy as to the structure of spikelets. The spikelets of H. sandwithii as described by Gilly are supposed to have “flores masculi 4-6 in parte spiculae inferiori,” a structure that fits neither Hypolytrum nor Mapania as these two genera have spikelets with 2 and 2 to 4 staminate flowers respectively. Another part of Gilly's description stating “flores feminei in parte spiculae superiori et media” gives the impression that a spikelet of H. sandwithii bears two pistillate flowers on the rhachilla toward the upper part. This is contradictory to the fundamental morphology of spikelets in the tribe Mapanieae, where a spikelet is terminated by a single pistillate flower. These errors have been corrected in the emended description.