Schoenus rigidus T.L.Elliott & Muasya, 2020

Elliott, T. L. & Muasya, A. M., 2020, A taxonomic revision of the Epischoenus group of Schoenus (Cyperaceae, tribe Schoeneae), South African Journal of Botany 135, pp. 296-316 : 308-309

5. Schoenus rigidus T.L.Elliott & Muasya , sp. nov.

Type: South Africa, Western Cape Province, 3322 (Oudtshoorn): Montagu Pass between Toll house and bridge, (‒CD), 28 Sep 1944, Fourcade 6472 ( BOL! [ BOL_5450 ], holo.; BOL! [ BOL_6107 ], K! [2 sheets], NBG! [ NBG_0181112 ], PRE! [ PRE_0239816 ], iso.) .

Caespitose, perennial graminoid, aphyllopodic ( Fig. 3E and 3J ). Culms (340 —)498 — 1166(‒1370) £ (0.3 —) 0.6 — 0.8 mm. Leaves usually absent, rudimentary if present, 27 — 30 £ 0.5 — 0.8 mm, straight, margins serrate. Sheaths reddish-black, longitudinally striate, open, central vein terminating in a mucro up to several mm long (when rudimentary leaf not present), firm. Ligule usually absent, (0.6 —)1.6‒ 2.8(‒3.0) mm if present. In fl orescence an erect pseudolateral panicle, (13 —)17‒21(‒24) £ 3.0‒5.0(‒8.0) mm, proximal rachis length (3.5 —) 4.8‒7.0(‒9.0) mm, proximal primary inflorescence bract appressed to central axis but subsequent bracts not ( Figs. 3J and 7E ). Proximal primary in fl orescence bracts (15 —)20‒25(‒32) mm long, narrow, lateral chartaceous extensions at base, involute, apex acute, exceeding length of inflorescence slightly. Spikes 2, (8 —)10‒13(‒18) mm long, aggregated into clusters along rachis, mostly overlapping. Spikelets linear-lanceolate to lanceolate, 1 — 4 spikelets per spike, (5.7 —)6.6‒7.4 (‒8.9) £ (1.1 —)1.4‒1.5(‒2.3) mm, pedicellate, colour reddish-brown, texture firm and opaque, slightly concealed by lateral chartaceous extensions of primary inflorescence bracts, varying number of sterile glumes at spikelet base ( Fig. 8E ). Proximal spikelet prophyll sometimes present, (0.7 —)1.5‒2.6(‒3.7) mm, mucros absent. Rachilla (0.6‒)1.6‒ 2.9(‒7.1) mm long. Glumes 5‒9 per spikelet, texture opaque and firm, sometimes with narrow hyaline margins, lower glumes varying in length, proximal glume (0.7‒)2.0‒2.9(‒3.9) mm long, subproximal glume (1.1‒)1.7‒2.9(‒5.3) mm long, upper glumes longer than basal ones, apex acuminate to obtuse. Glume mucros often absent, proximal mucro 0‒0.2(‒1.1) mm long, subproximal mucro 0‒ 0.6 mm long. Stamens 3 per floret, anthers 2.8‒3.3(‒3.7) mm long. Stigmas 3-branched, vestigial stigmas absent (i.e. yet to be observed). Perianth bristles absent (i.e. yet to be observed). Suprafloral axis sometimes thickening and strengthening, eventually curving. Nutlet 2.3‒2.7 £ 1.1‒1.4 mm, broad elliptic, trigonous, stipitate, shiny, yellowish in colour when young and turning reddish-brown with maturity; nutlet beak 0.1‒0.3 mm ( Fig. 10E ). ( Figs. 3 , 7 , 8 and 10 )

Flowering: May to October, but flowering specimens have also been collected in February

Distribution and ecology: Schoenus rigidus is known to occur relatively close to the southern coast of South Africa, with a reported distribution ranging from the Grahamstown area in the east to near George in the west ( Fig. 15 ). Based on herbarium label information, S. rigidus has been collected from both wet and dry habitats on mountainous slopes, flat areas and in forests. This species has a broad elevational tolerance, ranging from 75 — 1375 m.

Diagnosis: Other southern African Schoenus species closely resembling S. rigidus include S. selinae and S. schonlandii . Schoenus selinae also has lateral chartaceous extensions on the primary inflorescence bracts, but compared to S. selinae , the inflorescences of S. rigidus are more laterally branched. In addition, the chartaceous extensions of the primary inflorescence bracts tend to cover only the bases of the spikes in S. rigidus , whereas they cover more of the entire spike length in S. selinae . Schoenus schonlandii is a species partially overlapping in distribution; however, it lacks chartaceous extensions on the primary inflorescence bracts.

Additional collections examined

South Africa. EASTERN CAPE: 3323 (Willowmore): Kouga Mts., near Smutsberg , (‒CA), 12 Nov 1944, Esterhuysen 10,781 ( BOL) . 3326 (Grahamstown): Paradise Kloof , (‒BC), 31 May 1949, Rhodes University Collection 2910 ( BOL) ; kloof leading into Howieson's Poort , (‒BC), 25 Sep 1949, Rhodes University 3102 ( BOL) ; Osmunda Kloof ; marshy area near head of kloof, (‒BC), 25 Sep 1949, Martin 3102 ( GRA) ; Osmunda Kloof , S-facing slope, (‒BC), 8 Nov 2017, Elliott & Betz TE 2016_257 ( BOL) , Elliott & Betz TE 2016_258 ( BOL) , Elliott & Betz TE 2016_259 ( BOL) . 3424 (Humansdorp): Witte-Els Bosch, (‒AA), Jun 1921, Fourcade 1374 (BOL [2 sheets], K); P.E. to Storms River , Witelsbos , (‒AA), 13 Sep 1982, Getliffe 1155 ( NU) ; near Storms River , (‒BA), 3 Jul 1955, Levyns 10,245 ( BOL) ; Storms River Bridge, (‒BA), 24 Jul 1956, Levyns 10,483 ( BOL) ; Humansdorp , (‒BB), 17 Apr 1979, de Kock 20 ( PRE) . WESTERN CAPE: 3322 (Oudtshoorn): Montagu Pass , (‒CD), 21 Nov 1944, Esterhuysen 10,864 (BOL, K); 25 Jul 1956, Levyns 10,502 ( BOL) ; George, Forest Reserve , (‒CD), 3 Aug 1956, Levyns 10,575 ( BOL) . 3423 (Knysna): Noetzie , (‒AA), Apr 1925, Phillips 8A ( GRA) ; in forest near Brackenhill Falls , (‒AA), Jul 1946, Levyns 7861 ( BOL) ; Sparrebosch , (‒AA), 13 Jul 1946, Levyns 7868 ( BOL) ; near Noetzie , (‒AA), 30 Jul 1951, Levyns 9642 ( BOL) .

Figures

Fig. 3. Examples of plants from five species of the Epischoenus group found in southern Africa, showing the corresponding inflorescences beneath each plant: A and F—S. dregeanus; B and G—S.complanatus; C and H—S. quadrangularis; D and I—S.selinae; and E and J—S.rigidus. The black scale bar adjacent to the inflorescence in L represents 10 mm.

Fig. 7. Diagrammatic representations of the inflorescences of 11 species in the Epischoenus group, with spikelets illustrated in dark grey, primary inflorescence bracts in white and chartaceous (membranaceous) lateral extensions of the primary inflorescence bracts in light grey. Illustrations are not drawn to exact scale and stippling represents hairs. Inflorescences of the following species are shown: A—S. dregeanus; B—S. complanatus; C—S. quadrangularis; D—S. selinae; E—S. rigidus; F—S. crinitus; G—S. adnatus; H—S. gracillimus; I—S. schonlandii; J—S. lucidus; and K—S.neovillosus.

Fig. 8. Examples of spikelets from 11 species of the Epischoenus group found in southern Africa: A—S.dregeanus; B—S.complanatus; C—S. quadrangularis; D—S. selinae; E—S.rigidus; F—S.crinitus; G—S.adnatus; H—S.gracillimus; I—S.schonlandii; J—S.lucidus; and K—S.neovillosus. The black scale bar beside K represents 1 mm.

Fig. 10. Examples of nutlets from 11 species of the Epischoenus group found in southern Africa: A—S. dregeanus; B—S.complanatus; C—S. quadrangularis; D—S. selinae; E—S.rigidus; F—S.crinitus; G—S.adnatus; H—S.gracillimus; I—S.schonlandii; J—S.lucidus; and K—S.neovillosus. The black scale bar beside K represents 1 mm. Fully formed, mature nutlets of S.crinitus and S. neovillosus have yet to be observed.

Fig. 15. Documented locations of S.rigidus.