Thesium longicaule Zhigila, Verboom & Muasya, 2019

Zhigila, D. A., Verboom, G. A., Stirton, C. H. & Muasya, A. M., 2019, A taxonomic revision of Thesium section Hagnothesium (Santalaceae) and description of a new species, T. quartzicolum *, South African Journal of Botany 124, pp. 280-303 : 299

5.2.2.4. Thesium longicaule Zhigila, Verboom & Muasya nom. nov.

Basionym: Thesidium longifolium A.W.Hill in Bull. Misc. Inform. Kew 3: 99 (1915).

Thesium longifolium (A.W.Hill) J.C.Manning & F.Forest in Bothalia 43(2): 215 (2013); non Thesium longifolium Turcz. Published in: Bull. Soc. Imp. Natur. Moscou, 11: 100 (1838).

Type: South Africa. Western Cape, Cape Town (3318): Eastern side of Table Mountain (-AB), 365.8 m, July 1880, Bolus 4608 ( BOL! Holotype, HBG! K!, NBG!, PRE! Isolectotypes).

Bolus 4608 was designated as lectotype as it clearly shows the diagnostic characters and has female and male plants present.

A suberect or sprawling perennial suffrutex, 20–30 cm tall, heath-like or growing under other shrubs, green to yellowish green, brittle, particularly when dry, woody taproot with slender fibrous rootstock, branched mainly at base part, 3–15 branches, branching pattern fastigiate, leaves subtending each branchlet. Stems woody at base, herbaceous at distal portion, slender, 1.5–2.5 mm in diameter, sprawling or suberect, sub-hispidulous, conspicuously sulcate in transverse section. Leaves well developed, incurved to adpressed to the stem, golden green, tomentum shortly hispid, without prominent venation, midrib conspicuously raised, leaf apex acute, margins membranous, straight, rarely convex or concavely recurved. In fl orescences arranged along the branch length, in branchlet axils, in spikes, attached to the stem by a short or no pedicel; bracts and bracteoles leaf-like; bracts not fleshy, 5–10 × 2–2.5 mm, linear to acicular, margins entire, cartilaginous or membranous, golden green, acute at tips, longer relative to the flower, concave or convex; bracteoles bract-like but smaller, 3–4 × 0.4–2 mm; flowers campanulate, yellowish green, 2–3.7 × 0.8–1.5 mm, 4-merous, external gland between perianth lobes absent, perianth lobe segments 0.5–1.5 × 0.5–0.9 mm; lobes ovate to triangular, obtuse at tips, not distinctly uncinate, lobulate or straight, tubes inconspicuous. Male and female plants well differentiated. Male plant: branches more slender than female plants, internodes 4–10 mm long; leaves fewer, more slen-der than female leaves, acicular, 5–10 × 0.4–0.8 mm; inflorescences lax; stamen tetramerous, staminal filaments exserted at junction of hypanthium and perianth lobe tubes, hypanthium shallow, about 0.2 mm. Female plant: branches more robust, internode short compared to male counterpart, 1–5 mm; leaves sparse, not imbricate, linear, 8–19 × 0.5–1.5 mm; inflorescences lax; hypanthium tube length less than the perianth lobe tubes; style stout, between 0.2 and 0.4 mm. Fruit a nutlet, subglobose, green, attached to the branch by a white attenuated elaiosome, 1.8–2.5 × 1.7–2 mm, with 10 conspicuous ribs and reticulate veins between ribs, capped with green persistent perianth lobe segments, shorter relative to the fruit length ( Fig. 13 ).

5.2.2.4.1. Diagnostic characters. Thesium longicaule is easily confused with T.fruticulosum or T. hirtum as all have fastigiate branching patterns, leaf-like bracts and bracteoles subtending inflorescences, flowers in spikes, and 10-ribbed fruits with conspicuous veins running between longitudinal ribs. By contrast, T. longicaule differs from both being more slender, particularly the male plants (versus robust), brittle (versus not brittle), with wider internodes, 4–10 mm long (versus internodes short to almost absent, 0.2–2 mm long), stems sulcate with ridge edges sub-hispidulous (versus glabrous in T. fruticulosum and scabrous in T. hirtum ), and leaves sparse, linear or acicular, concave or convex (versus many, dense, almost overlapping straight, rarely incurved in T. fruticulosum and T. hirtum ).

5.2.2.4.2. Distribution and habitat. Thesium longicaule occurs on sandstone in mountain fynbos and on sandstone flats and slopes of the GCFR from the Cederberg to the Swartberg, on rocky mountain slopes. It has been collected in the Olifants Sandstone Fynbos and Cederberg Sandstone Fynbos, North Outeniqua Sandstone Fynbos, South Outeniqua Sandstone Fynbos vegetation ( Fig. 7F ,solid triangles) between elevation 150 and 1200 m.

5.2.2.4.3. Conservation status. With the distinction of T. longicaule from T. fruticulosum , the conservation status of T. longicaule is here assessed as LC (Least concern) as it is abundant over its local geographical range ( IUCN Standards and Petitions Subcommittee, 2017).

5.2.2.4.4. Additional specimens studied. South Africa. WESTERN CAPE: 3218 ( Clanwilliam ): Olifants Rivier, (- DB) , 03 Dec 1950, ♀ plants, Esterhuysen 17862 ( BOL) . 3318 (Cape Town): Table Mountain (- AB) , Dec 1924, ♀ plants, Compton 2117 ( BOL) ; Oct 1940, ♀ plants, Esterhuysen 23237 ( BOL) . 3321 ( Ladismith ): García's Pass (- CC) , 22 Mar 1938, ♀ plants, Compton 8156 ( BOL) . 3322 ( Oudtshoorn ): near Groeneweide Park (- CD) , 03 Dec 1950, ♀ plants, Esterhuysen 17863 ( BOL) . 3418 ( Simonstown ): Near Muizenberg Reservoir (- CA) , 22 Jan 1933, ♂ plant, Salter 2954 ( BOL) ; N of Window stream, Kirstenbosch (- AB) , Jul 1880, ♂ & ♀ plants, Bolus 4608 ( BOL) Contour path near, Kirstenbosch , (- CC) , no precise date, ♂ plant, Compton 8187 ( BOL) ; upper Kirstenbosch, near Diamond stream (- CD) , 22 Mar 1938, ♂ & ♀ plants, Compton 8157 ( BOL) . 3419 (Caledon): Lebanon catchment II (- AA) , 11 Nov 1967, ♂ & ♀ plants, Kruger 562 ( PRE) ; Hermanus (- AB) , 21 Dec 1942, ♂ & ♀ plants, Compton 14, 253 ( NBG) ; Betty's Bay , 02 Feb 1961, ♂ & ♀ plants, Levyns 11, 125 ( BOL) .

Figures

Fig. 13. Thesium minus: (A) post-fire habit, based on Esterhuysen 32490a (K!), (B) detailed rhizomatous stem and roots, (C) male flowering shoot, (D) a female fruiting shoot, (E) fruits. Photographs:Daniel Zhigila.

Fig. 7. Distribution of species of Thesium section Hagnothesium: (A) T.fragile, (B) T.fruticulosum, (C) T.microcarpum, (D) T.minus, (E).T.hirtum •, T.quartzicolum ▲, (F) T.leptostachyum •, T. longicaule ▲.