Schoenus exilis (Levyns) T.L.Elliott & Muasya, S.

Elliott, T. L., Barrett, R. L. & Muasya, A. M., 2019, A taxonomic revision of Schoenus cuspidatus and allies (Cyperaceae, tribe Schoeneae) - Part 1 *, South African Journal of Botany 121, pp. 519-535 : 527-528

4. Schoenus exilis (Levyns) T.L.Elliott & Muasya, S. African J.Bot.112: 359 (2017).

Tetraria exilis Levyns, J. S. African Bot. 13: 88 (1947).

Type: South Africa, Western Cape Province, 3318 (Cape Town): Camps Bay, (–CD), 18 May 1941, Levyns 7566 (BOL, holo! [BOL139424]; BOL! [BOL139425], iso.).

[Note: Nees (1835c) cited Sieber 107 (BM, H[H 1454909], K[K000244953, K000244956], S[S 13-18896]) in his protologue of Elynanthus gracilis Nees. This collection has been identified as S. exilis after examination of the specimens from BM and K by T.L. Elliott. However, Sieber 108 (BM, S[S 13-18897, S 13-18898]) — which was also cited in the same protologue—appears to be a specimen of S. cuspidatus or a closely related species that will need to be resolved through revision of that species complex. Since E. gracilis is already a synonym of T. cuspidata (see Elliott and Muasya, 2017), and the original species description does not clearly correspond to our circumscription of S. exilis , we have decided to maintain E. gracilis as a synonym of S. cuspidatus and preserve the name S. exilis .].

Caespitose, phyllopodic perennial graminoid. Culms terete, relatively short, (77–)202–340 × 0.2–0.6 mm. Leaves basal, 1–3(—5), (17–) 62–112(—164) × 0.2–1.5 mm, usually straight, proximally channelled, margin usually serrate above sheath. Sheaths firm, reddish-brown, longitudinally striate. Ligule ranging from a membranaceous flap to firm, 0.1–1.0(—2.2) mm long. In fl orescence a narrow, pseudolateral panicle, 12–25(—45) × 2–7 mm, proximal rachis length varying in length, 5–10(—23) mm. Proximal primary in fl orescence bracts sometimes channelled proximally, apex acute to acuminate, not widened at base, (13–)24–35(—57) mm long, exceeding length of inflorescence, longitudinal veins not notable. Proximal and subproximal primary inflorescence bracts without membranaceous extensions at base. Spikes 2–5 (—11), (3.0–)6.0–17.0 mm long, usually dispersed along rachis. Spikelets linear-lanceolate to lanceolate, relatively short, 3.4–4.9 × 0.6–1.2 mm, pedicellate, 1–4(—6) spikelets per spike. Proximal spikelet prophyll 1 per spikelet, with thin inconspicuous vein extending to mucro, 0.1–1.0 mm long, prophyll mucro 0.8–2.2(—4.0) mm long. Rachilla (0.3–)1.0– 2.7 mm long. Glumes 4–6(—8) per spikelet, proximal glume 0.6–2.4 mm long, subproximal glume 1.0– 2.5 mm long, upper glumes longer than basal ones, lower glumes rarely over half the length of spikelet, thin hyaline margins, apex obtuse. Glume mucros absent or short, proximal mucro 0.2–0.8(—2.1) mm long, subproximal mucro 0.1–1.4 mm long. Stamens (2–)3 per floret, anthers vary in length, 1.3–2.2(—3.7) mm long. Stigmas 3-branched, vestigial stigmas of second bisexual floret not observed. Perianth bristles not observed. Nutlet narrow elliptic, trigonous, yellowish in colour, 1.8–2.6 × 0.3–0.9 mm. Nutlet beak 0.1–0.4(—1.0) mm long, hispid ( Figs. 2 and 3 ).

Flowering: April–May

Distribution and ecology: Schoenus exilis is found throughout the western part of the Western Cape Province of South Africa ( Fig. 11 ), primarily on dry to damp sites on sandstone-derived soils, but it has also been collected from granite-derived soils. The elevational range of S. exilis is from near sea level to over 400 m.

Diagnosis: The most notable characters of S.exilis are its narrow elliptic nutlets and narrow, lanceolate spikelets. Schoenus ligulatus also has narrow elliptic nutlets; however, it is a taller species (> 350 mm) compared to the shorter S. exilis (<350 mm). Although the spikelets of these two species are similar in shape, those of S.exilis tend to be shorter (mostly <4.5 mm in length), whereas those of S. ligulatus are longer (> 4.5 mm in length). Schoenus quartziticus has lanceolate spikelets that are similar in length to those of S. exilis , but that species has a broad elliptic nutlet and not the narrow elliptic nutlet of S. exilis ( Fig. 2 ).

Variation in spikelet shape and ligule type occur throughout the range of S. exilis , with no distinct breaks allowing the delineation of separate species ( Fig. 12 ). After a close inspection of specimens throughout the range of S.exilis , it appears that the wider lanceolate spikelets of the type specimen of the species (Levyns 7566) are rare compared to the spikelets of other specimens from throughout the range of the species, which tend to be linear-lanceolate. Furthermore, most specimens collected from more easterly locations tend to have a short, membranaceous ligule, while the ligule of the type specimen is firm. Specimens studied from the Cape Peninsula and surrounding areas display both firm and membranaceous ligules, as well as linear-lanceolate and wide lanceolate spikelets; however, as one proceeds eastward and northwards there is a trend towards membranaceous ligules and lanceolate spikelets.

Additional collections examined

South Africa. WESTERN CAPE: 3318 (Cape Town): Camps Bay , (– CD), 4 Apr1937, Levyns 6046 ( BOL) ; 18 May 1941, Levyns 7566 ( BOL [2 sheets]); without date, Burchell 313 ( K); Kirstenbosch, lower slopes N. of Window Stream , cleared of pines, (–CD), April 1946, Esterhuysen 12,761 ( BOL) ; Kirstenbosch, clearing N. of Window Stream , (–CD), April 1946, Esterhuysen s.n. ( BOL) ; Restio harveyi site at Fiskaal Rd. above Camps Bay, (–CD), 5 May 1976, Esterhuysen 34,284 ( BOL, K); First River terrace, Stellenbosch Flats , (–DD), May 1925, Duthie 1633 ( BOL) ; Jonkershoek, Jakkalsvlei , (–DD), 4 Apr 1963, Taylor 4666 ( NBG, PRE) . 3319 (Worcester): Slanghoek Mts., Krom R. Dome , (–CA), 31 Mar 1945, Esterhuysen 11,518 ( BOL, K); Limietberg Nature Reserve , Happy Valley trail, (–CA), 27 Apr 2017, Elliott, Muasya & Betz TE2016_189 ( BOL) ; Riviersonderend Mountains , N. slopes immediately below radio mast on Jonaskop , (–DC), 30 Jan 2004, Verboom 694 ( BOL) . 3418 (Simonstown): near Constantia Nek , (–AB), May 1923, Adamson s.n. ( BOL) ; Muizenberg , (–AB), 9 May 1937, Levyns 6229 ( BOL) ; Froggy Farm , (–AB), 2 Apr 1965, Taylor 6231 ( NBG) ; Silvermine Nature Reserve , Steenberg Peak area , (–AB), 9 Jun 2002, Verboom 535 ( BOL) ; Table Mountain , Back Table , E. slope of Grootkop , (–AB), 1 Dec 2002, Verboom 623 ( BOL) ; Silvermine Nature Reserve , Silvermine West , c. 650–700 m to S.W. of reservoir on Noordhoek Peak trail, (– AB), 6 Jun 2017, Elliott, Muasya & Muthaphuli TE2016_192 ( BOL) ; ‘ in summo monte Constantiaberg’ , (–AB), 6 Mar 1892, Schlechter 440 ( BOL) ; Steenbras area , (–BB), 1 May 1948, Levyns 8868 ( BOL) , Levyns 8869 ( BOL [2 sheets]); Upper Harmony Flats between Lwandle Township and Strand foam factory, (–BB), 5 Jan 1978, Boucher 3436 ( NBG) ; Palmiet River, (–BD), 4 Feb 1896, Schlechter 7325 ( BM, BOL, K, NSW, SAM, WAG); Palmiet River Mouth, (– BD), Feb 1940, Levyns 7172 ( BOL) ; Feb 1943, Levyns 8712 ( BOL) ; 17 Feb 1948, Levyns 8809 ( BOL) ; 6 May 1948, Levyns 8887 ( BOL [2 sheets]); Palmiet River , near quarry, (–BD), 19 Feb 1957, Levyns 10,638 ( BOL) ; Kogelberg Forest Reserve , Platberg plot (03/28), (–BD), Feb 1968, Boucher 33 ( NBG) ; Kogelberg Nature Reserve , near Highlands parking area, (–BD), 17 Nov 2002, Verboom 610 ( BOL) ; c. 3–3.5 km S.E. of Rooi Els: about 100–200 m E. of R44, on S. side of small road heading to Kogelberg Sonchern Link Nature Reserve , (–BD), 18 Nov 2016, Elliott & Muasya TE2016_138 ( BOL) ; Kogelberg Nature Reserve , along small vehicle trail between Kogelberg Nature Reserve Reception and Louwsrivier, (–BD), 18 Nov 2016, Elliott & Muasya TE2016_157 ( BOL) . 3419 (Caledon): Palmiet River, Elgin , (– AA), Dec 1941, Stokoe 8458 ( BOL) ; Elgin Basin, Arieskraal Farm (portion Solva ), on Bokkeveld Shales in horseshoe bend of Palmiet River , (–AA), 24 Apr 1993, Rode & Boucher 101 ( NBG) ; Hottentots Hollands Nature Reserve , c. 800 m from Nuweberg parking lot along jeep track to Landdroskop Hut , (–AA), 18 Feb 2017, Elliott & Muasya TE2016_170 ( BOL) ; Highlands Forest Reserve , Perdeberg , (–AC), 10 May 1982, Getliffe 1108 ( NU) , Getliffe-Norris 1108 ( PRE) ; on a mountain near Genadendal, (–BA), 12 Apr 1811, Burchell 8622B ( K); Rooi Els , (–BD), 2 May 1949, Levyns 9390A ( BM) ; slopes near Rooi Els , (–BD), 2 May 1949, Levyns 9390A ( BOL) ; Rooi Els – lower slopes, (–BD), 2 May 1949, Levyns 9390A ( BOL) ; sandy foothills of Soetanysberg on farm Hangnes , (–DB), 24 Mar 1982, van Wyk 887 ( NBG) .

Figures

Fig.2. Examples of nutlets from 11 species of the Schoenus cuspidatus and allies group found in southern Africa:A—S.auritus; B—S.graminifolius; C—S.ligulatus; D—S.exilis; E—S.bolusii; F— S.submarginalis; G—S.crassiculmis; H—S.quartziticus; I—S.limosus; J—S.purpurascens; and K—S.calceolus (immature).The black scale bar represents 1 mm.The mature fruits of S.calceolus and S.prophyllus are unknown.

Fig.3. Examples of plants from six species of the Schoenus cuspidatus and allies group found in southern Africa,showing the corresponding inflorescences andspikelets beneath each plant: A, G and M—S.auritus; B, H and N—S.graminifolius; C, I and O—S. ligulatus; D,J, and P—S.exilis; E,K and Q—S.bolusii; and F, L and R—S.submarginalis. The black scale bar adjacent to the inflorescences in G—L represents 10 mm, while the scale bars adjacent to the spikelets in M—R represent 1 mm.

Fig. 11. Documented locations of Schoenus exilis.

Fig. 12. Variation in plant habit and inflorescences in Schoenus exilis, where A illustrates the habit and C the inflorescence of the less robust form of the species, while the habit and inflorescence shape of the more robust form are illustrated in B and D. The black scale bar adjacent to the inflorescences represents 10 mm.