Schoenus nigricans, L.

Elliott, T. L. & Muasya, A. M., 2017, Taxonomic realignment in the southern African Tetraria (Cyperaceae, tribe Schoeneae; Schoenus clade) *, South African Journal of Botany 112, pp. 354-360 : 356

6.1. Schoenus nigricans L.

Schoenus nigricans ( Fig. 2A ) is the type species of one of the first 100 genera described by Linnaeus ( Linnaeus, 1753; Hitchcock, 1923), and a formal lectotype of this species was later designated by Simpson based on a Linnean specimen (LINN 68.6) collected from Gotland, Sweden ( Åsberg and Stearn, 1973; Jarvis, 1993). Key characters of S.nigricans include black basal sheaths that are notably wider than the leaf blades and loosely ovoid inflorescences with one or two bracts ( Tucker, 1993). In addition, S. nigricans generally has 10–25 flattened, oblong-ellipsoid spikelets with two to three sterile basal scales ( Fig. 2F ), as well as three to eight medially 1-veined floral scales (i.e. glumes) with acute apices ( Tucker, 1993). Furthermore, S. nigricans plants have whitish, ovoid to ellipsoid achenes that are glossy with obtuse apices ( Tucker, 1993).

Schoenus nigricans is a sub-cosmopolitan species found in North America, Eurasia, Africa and Australia, often found growing in damp grasslands ( Fig. 3a : Tucker, 1993; Goetghebeur, 1998). In South Africa, S. nigricans specimens have been recorded and databased from the Western and Eastern Cape provinces (Copenhagen: Global Biodiversity Information Facility, 2014).

Figures

Fig. 2. Examples of plants from each of the four clades of Schoenus found in southern Africa, showing the corresponding spikelets beneath each plant: A and F—S. nigricans, B and G—T.compar, C and H—Epischoenus sp. and D and I—T.cuspidata.A ‘reticulate-sheathed’ Tetraria of the Tricostularia clade is shown in E, with its spikelet shown in J.The black scale bar beneath the spikelets in F–J represents 1 mm.

Fig. 3. Documented locations of Schoenus nigricans and accepted southern African Tetraria and Epischoenus species in the Schoenus clade of Cyperaceae, based on data downloaded from GBIF (Copenhagen: Global Biodiversity Information Facility, 2014). The following groups of species are included in each map: A, S.nigricans; B, T. compar and allies; C,Epischoenus and allies; and D,T.cuspidata and allies. Schoenus nigricans has a cosmopolitan distribution (A), whereas the distribution of the other three groups is limited to southern Africa (B, C, and D).