Monographs Details: Exochogyne amazonica C.B.Clarke
Authority: Maguire, Bassett. 1965. The Botany of the Guayana Highland. Mem. New York Bot. Gard. 12 (3): 1-285.
Description:Distribution and Ecology - Distribution. K n o w n from relatively few localities in eastern Guayana from Cerro Duida eastwards to Tafelberg in Suriname and southwards to the Rio Negro Valley. VENEZUELA. Amazonas: between Esmeralda Savanna and southeastern base of Cerro Duida, alt. 200 m, Steyermark 57805 (F, holotype of E. amazonica var. esmeraldensis; N Y , isotype); between Esmeralda Savanna and southeastern base of Cerro Duida, in swampy woods, alt. 200 m, Steyermark 57820 (F, holotype of S. steyermarkii; N Y , photo). Bolivar: Sabana de Triana, Rio Chicanan, 50 k m S E of El Dorado, alt. 300 m, Steyermark 89696; Alto Rio Cuyuni, Rio Chicanan, in savannas 2 k m S of Rio Chibau, at alt. 100 m, Maguire, Steyermark & Maguire 53554; infrequent in savanna thickets, on SE escarpment of Cerro Piton, alt. 400 m, Cordillera Epicara, Maguire, Steyermark & Maguire 53650. BRITISH GUIANA. Potaro River, Kaietuk Savannah, in rather open dry sandy ground, Tutin 634 (BM, holotype of E. megalorrhyncha; K, isotype) ; Kaieteur Savanna, on sphagnum and damp sandy ground, ca. alt. 1200 ft, Sandwith 1405 (K, N Y ). SURINAME. Tafelberg: small savanna NW of Savanna No. VIII, Maguire 24433; grassy area in small rock savanna, low bush 0.5 km NW of Savanna No. VIII, alt. 760 m, Maguire 24601.
Discussion:Lagenocarpus amazonicus (C. B. Clarke) H. Pfeiffer in Fedde, Eepert. Sp. Nov. 21: 35. 1925.
ExocTiogyne megalorrhyncha Tutin, Hook. lc. Plant. 33: t. 3374. 1935. Syn. nov.
Exochogyne decandra Tutin, Hook. lc. Plant. 33: *. 3375. 1935. Syn. nov.
ExocTiogyne amazonica C. B. CI. var. esmeraldensis Gilly, Pieldiana Bot. 28(1): 53. 1951. Syn. nov.
Exochogyne steyermarTcii Gilly, Pieldiana Bot. 28(1): 53. 1951. Syn. nov.
In the genus Exochogyne four names have been proposed, viz. E . amazonica, E. decandra, E. megalorrhyncha, and E. steyermarkii. W e interpret all of them as representing the same taxon, of which the correct name should be E. amazonica. Tutin, who is responsible for two of these names, is of opinion that species of Exochogyne can be discerned by the mode of pubescence of leaves and the number of staminate and pistillate spikelets in an involucre. He then segregated E. decandra from E. amazonica by the number of staminate and pistillate spikelets that are 10 vs. 6 and 3 vs. 2 respectively. E . megalorrhyncha Tutin was separated from the above two chiefly by the long-pilose leaves, as contrastive with glabrous or nearly glabrous ones, and by the number of staminate spikelets that is 2 to 4 vs. 6 to 10. The last name, E. steyermarkii Gilly, was said to differ from E. megalorrhyncha in ''glabrity" of habit. But as shown in the scatter diagram of Fig. 9 and in Table 4, columns 1 and 3, none of these characters is clearcut, nor is there any correlation between the mode of pubescence and the number of staminate and pistillate spikelets in an involucre. Furthermore, we have also investigated the variability in the number of stamens in a flower and fruit size (see Table 4, columns 2 and 4), which we found useless for making taxonomic distinction.
Distribution:Guyana South America
| Suriname South America
| Venezuela South America