Schoenus riparius T.L.Elliott & Muasya, S.

Elliott, T. L. & Muasya, A. M., 2020, A taxonomic revision of Schoenus cuspidatus and allies (Cyperaceae, tribe Schoeneae) - Part 2, South African Journal of Botany 130, pp. 327-347 : 344-345

8. Schoenus riparius T.L.Elliott & Muasya, S. African J. Bot. 112: 359 (2017).

Tetraria paludosa Levyns, J. S. African Bot. 13: 85 — 87 (1947).

Type: South Africa, Western Cape Province, 3318 (Cape Town): Camps Bay, round edge of a marshy spot, (— CD), 28 Oct 1945, Levyns 7915 (BOL!, holo. [ BOL139430 ]).

Tetraria cuspidata (Rottb.) C.B.Clarke f. robustior K uk €., Repert. Spec. Nov. Regni. Veg. 29: 187 (1931). Type: South Africa, Western Cape Province, 3419 (Simonstown): Hout Bay, (— AB), 10 Jan 1921, Pillans 4864 (BOL!, lecto. [ BOL5071 ], here designated; K! [K000244907], iso.). [Note: K ukenthal € (1931) cited two specimens that he had examined under this taxon: Zeyher 84 and Pillans 4864. We were not able to locate Zeyher 84, so it is not possible to confirm if it is S. riparius , although it was collected from ‘Tafelberg’ (Table Mountain), which is from the same region as Pillans 4864.].

[Note: A lectotype was designated by T.L. Elliott as neither of the two specimens collected by Pillans were stored at B (the herbarium of the Botanic Garden and Botanic Museum Berlin-Dahlem) — the herbarium where K ukenthal € primarily worked. It is possible that K ukenthal € did examine Pillans 4864, and it was later destroyed during World War II.].

Caespitose, phyllopodic perennial graminoid, tall and robust ( Fig. 4C ). Culms terete, robust, relatively tall for this clade, (390 —) 630 — 886(— 1030) X (0.8 —)1.3 — 1.9(— 2.3) mm. Leaves basal, less than half the culm height or more, 1 — 2, (62 —)230 — 540(— 715) X 0.6‒0.9 (— 1.3) mm, straight, proximally channelled, margin serrate above sheath. Sheaths dark reddish-black at base but paler above, firm, longitudinally striate. Ligule 2-lobes not evident, firm, relatively short, 0.5 — 1.0(— 1.3) mm long. In fl orescence a pseudolateral panicle, long, dense and relatively wide, with many spikes, (49 —)60‒89 (— 114) X (6 —)12‒15(— 19) mm, proximal rachis length (20 —)28‒40 (— 53) mm ( Fig. 4G ). Proximal primary in fl orescence bracts firm, apex acute to acuminate, usually channelled, narrow at base, (80 —)96‒167 (— 204) mm long, exceeding length of inflorescence at least slightly. Spikes often many and aggregated into dense clusters along rachis, 5‒13, (9.0 —)12.0‒18.0(— 24.0) mm long, overlapping. Spikelets lanceolate, aristate, (4.8 —)5.4‒5.9(— 6.2) X 1.0‒1.4(— 1.6) mm, pedicellate, 2 — 4 spikelets per spike, dark reddish-brown in colour ( Fig. 5H ). Proximal spikelet prophyll 1 per spikelet, well-developed, with notable, raised vein extending to mucro, 0.8‒1.0(— 1.6) mm long, prophyll mucro sometimes long giving inflorescence a ‘bearded’ appearance, (1.8‒)2.9‒4.4(— 6.4) mm long. Rachilla (0.4‒)1.0‒2.1(— 3.5) mm long. Glumes 5‒8 per spikelet, proximal glume (0.8‒)1.3‒1.8(— 2.2) mm long, subproximal glume (1.0‒)1.4‒1.7(— 2.5) mm long, narrow hyaline margins, upper glumes longer than basal ones, apex acute to obtuse. Glume mucros shortly cuspidate, proximal mucro (0.3‒)0.9‒ 1.5(— 2.2) mm long, subproximal mucro (0.1‒)0.1‒0.7(— 0.9) mm long. Stamens 1‒3 per floret (usually 3), anthers 2.5‒3.0 mm long. Stigmas 3-branched, vestigial stigmas of second bisexual floret absent (i.e. yet to be observed). Perianth bristles absent (i.e. yet to be observed). Nutlet broad elliptic, trigonous, yellowish in colour when young but maturing to reddish-brown in colour, 2.3‒3.2(— 3.8) X 0.7‒ 1.3 mm ( Fig. 6H ). Nutlet beak 0.8‒1.5(‒2.5) mm long, hispid.

Flowering: October

Distribution and ecology: Schoenus riparius has been reported from two locations (Camps Bay and Hout Bay) on the Cape Peninsula of South Africa ( Fig. 15 ). Collections of this species have been made from damp sites between 150 and 200 m.

Schoenus riparius was last collected in 1946, and its existence has not been confirmed since that year. Recent searches by T.L. Elliott in 2017 and 2018 in the Camps Bay and Hout Bay areas were not able to locate this species. Land transformation on the Cape Peninsula has reduced the amount of suitable habitat for S. riparius , so there is the possibility that S. riparius is now extinct.

Diagnosis: Schoenus riparius is a robust species, with relatively long and wide panicles ( Fig. 4C and G ). It is most like S. loreus , but it has channelled leaves that become terete distally compared to the non-channelled and flat leaves of S. loreus ( Fig. 3D ). Schoenus australis is also a relatively large and robust species ( Fig. 4D ), but it occurs on sites with coarse-textured soils, whereas S. riparius occurs on damp sites on the Cape Peninsula. The inflorescences of S. australis ( Fig. 4H ) are also shorter and thinner compared to those of S. riparius . Schoenus crassus is a third species that could be confused with S. riparius ; however, S. crassus usually has firmer and stiffer basal leaves ( Fig. 3C ) compared to those of S. riparius . In addition, S. crassus has lighter reddish-brown coloured culm bases, inflorescences and spikelets than S. riparius ( Figs. 3 , 4 and 5 ).

Levyns (1947) described the spikelets of S. riparius as cuspidate; however, the spikelets examined by T.L. Elliott were more aristate in shape.

Additional collections examined

South Africa. WESTERN CAPE: 3318 (Cape Town): Camps Bay, (— CD), 19 Oct 1946, Levyns 8721 ( BOL, K); 17 Nov 1946, Levyns 8715 ( BOL [2 sheets], K); ‘ Ad lat. Mont tabular. Infra Vam Campsbay’ , (— CD), Jul without year, Zeyher 4432 ( SAM) .

Figures

Fig. 4. Examples of plants from four species of the S.cuspidatus and allies group found in Southern Africa, showing the corresponding inflorescences beneath each plant: A and E—S. cuspidatus; B and F—S.graciliculmis; C and G—S.riparius; and D and H—S.australis. The black scale bar adjacent to the inflorescence in H represents 10 mm.

Fig. 5. Examples of spikelets from nine species of the S. cuspidatus and allies group found in Southern Africa:A—S. brunnescens; B—S. compactus; C—S. crassus; D—S.loreus; E—S. gal- pinii; F—S.cuspidatus; G—S.graciliculmis; H—S.riparius; and I—S.australis. The black scale bar represents 1 mm.

Fig. 6. Examples of nutlets from nine species of the S.cuspidatus and allies group found in Southern Africa:A—S. brunnescens; B—S. compactus; C—S. crassus; D—S. loreus; E—S. galpinii; F—S.cuspidatus; G—S.graciliculmis; H—S.riparius; and I—S.australis. The black scale bar represents 1 mm.

Fig. 15. Documented locations of S.riparius.

Fig. 3. Examples of plants from five species of the S. cuspidatus and allies group found in Southern Africa, showing the corresponding inflorescences beneath each plant: A and F—S. brunnescens; B and G—S.compactus; C and H—S.crassus; D and I—S.loreus; and E and J—S.galpinii. The black scale bar adjacent to the inflorescence in J represents 10 mm.