Maguire, Bassett. 1972. The botany of the Guayana Highland--part IX. Mem. New York Bot. Gard. 23: 1-832.
Cyperaceae
Distribution and Ecology - Distribution. Widespread from southern Mexico and West Indies, through the Guayana and the Guiana regions and lower Andean region southwards to southern Brazil and northern Argentina. The following are the specimens examined from the Guayana and the Guiana regions. VENEZUELA. Táchira: between Tabor and Villapaez, along Rio Tachira, along Colombia-Venezuelan boundary, 1820-2130 m alt, Steyermark 57155 (F, NY); Monagas: ca 7.5 km SW of Santa Barbara, 245 m alt, Pursell et al 8287 (NY); Sucre: Isla de Margarita, 600 m alt, Johnston 310 (GH, NY); Bolívar: Auyan-tepuí, near El Geñoá, 1600 m alt, Schnee 1653 (MAR), Savanna between Hato de Nuria and Quebrada Caballape, 380 m alt, Steyermark 88700 (NY, VEN), Roraima formation in the valley of Río Cuyuní, 130-131 km S of El Dorado, 1290-1300 m alt, Steyermark et al 104086 (NY, VEN), Sororopán-tepuí, crest of cerro between east and west end, 2255 m alt, Steyermark 60115 & 60146 (F, NY), Mt. Roraima, Glycon Swamp and vicinity, 1830-1920 m alt, Steyermark 58627 (F, NY), 102 km from El Dorado toward Santa Elena, Foldats 2887 (VEN), Cerro Upuima, 1300 m alt, Cardona 2230 (VEN), Trail between Km 134 and 150, near headwaters of Río Aponguao, NE of Luepa, 1200 m alt, Steyermark & Nilsson 727 (NY, S, VEN). GUYANA. Upper Mazaruni River Basin, Ayanganna Plateau, Haieka Savanna east side of Haieka River, Tillett & Tillett 45211 (NY), East Coast Water Conservancy, SE of Georgetown, canal SE of Lamaha Drop-off, Hitchcock 16990 (NY).
Syntype consisting of Martius 3193 (M, lectotype chosen here) from Sebastianopolis, Rio de Janeiro, Brazil; Sellow (B) from San Antonio do Monte, Rio Grande do Sul, Brazil; and Macrae (K) from Bahia, Brazil.
[Schoenus marisculus Lindley ex Nees, FI. Brasil. 2(1): 142. 1842. Invalid name published as a synonym.]
[Rhynchospora rigida Schrader ex Nees, FI. Brasil. 2(1): 142. 1842. Invalid name published as a synonym.]
Rhynchospora jubata Liebmann, Kongl. Dansk. Vidensk. Selsk. Skrift. 5(Afd. 2): 254. 1851. Type. Liebmann (C, NY) from S. Antonio Hautusco, Mexico.
Rhynchospora tenuiseta C. Wright ex Sauvalle, Anal. Acad. Ci. Med. Fis. Nat. Habana 8: 83. 1871. Type. C. Wright 5870 (GH) from Cuba.
Rhynchospora marisculus Nees var elatior Böckeler, Vidensk. Meddel. 1869(9-13): 149. 1869. Type. Warming (C) from Lagoa Santa, Brazil.
Rhynchospora uleana Böckeler, Allg. Bot. Zeitschr. 2: 110. 1896. Type. Ule 1394 (B) from Tubarao, Santa Catarina, Brazil.
Rhynchospora weberbaueri C. B. Clarke, Bot. Jahrb. 37: 518. 1906. Type. Weberbauer 4765 (B) from Berge östlich von Moyobamba, Loreto, Peru.
Rhynchospora borinquensis Britton, Bull. Torrey Club 42: 387. 1915. Type. Shafer 3515 (NY) from Rio Icaco and adjacent hills, Sierra de Naguabo, Puerto Rico.
Dichromena marisculus (Nees) Macbride, Publ. Field Mus. Bot. 11: 5. 1931. Based on Rhynchospora marisculus Nees.
Type. Martius 3193 (M, lectotype) from “pratis sylvaticis ad Sebastianopolis, prov. Rio de Janeiro,” Brazil.
In Venezuela, this species has previously been reported only from Isla de Margarita, Sucre. The specimens cited above indicate that it actually occurs quite widely in Venezuela.
The differentiation between R. marisculus and R. rugosa is often difficult. According to Kükenthal, who classified the two into different sections, the achenes of R. marisculus are coarsely rugose with few transverse ridges, while those of R. rugosa are rugose with many transverse ridges. In my opinion, this difference in achenes’ surfaces is invalid, since the achenes of both species are extremely alike and are wrinkled, with 10 to 16 ridges making no such difference. Gale separated these two species chiefly on the basis of the shape of style-bases in addition to the length of perianth bristles relative to the height of the style-base, ie, in R. marisculus, the deltoid attenuate style-bases are well exceeded by the bristles, while in R. rugosa, the deltoid style-bases are equalled or are only slightly exceeded by the bristles. The difference in the shape of the style-bases is acceptable, since the elongated style-base in R. marisculus ranges from 0.8 to 1 mm in length in contrast to the short ones in R. rugosa, ranging from 0.3 to 0.6 mm in length. However, whether or not the style-bases are surpassed by the bristles becomes rather vague in South American plants because one population of R. rugosa, generally classified as R. brasiliensis, bears appreciably elongated bristles that conspicuously surpass the style-base.
My own observation adds a few more points of distinction. In R. marisculus, its lanceolate to lance-oblong spikelets are 6 to 8 mm long, its rusty- or somewhat straw-brown fruiting glumes are 5 to 6 mm long by 1-1.2 mm wide, and its elliptic-obovate achenes are usually 0.9 to 1.2 mm wide, whereas in R. rugosa, its ovoid spikelets are 4 to 5 mm long, its ovate to elliptic ovate fruiting glumes are 3 to 4 mm long by 1.7 to 2 mm wide, and its obovate achenes are as a rule more than 1.2 mm wide. In normally developed individuals, the culms of R. marisculus attain the height of 1.2 to 2 m, while in R. rugosa, the culms are 0.5 to 1.3 m high. The two species in discussion are without doubt very closely related to one another, and, therefore, I am in agreement with Gale in placing them in the same section.
Examination of an isotype of R. jubata of Mexico confirms Kükenthal’s assumption that it is identical with R. marisculus.
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