Ruschia promontorii L.Bolus (1929: 121)

Klak, Cornelia, Schmiedel, Ute & Bruyns, Peter V., 2020, The taxonomic status of Ruschia stricta var. turgida and R. promontorii and a new name for R. vaginata (Ruschieae, Aizoaceae), Phytotaxa 433 (1), pp. 41-54 : 49-50

Ruschia promontorii L.Bolus (1929: 121) .

Type:— SOUTH AFRICA. Western Cape, Simonstown (3418): Cape Peninsula , near Cape Point (- AD), sine die, Rohland sub NBG 1543 /20 (holotype BOL134494 !, the holotype can be viewed at https://plants.jstor.org/search?filter=name&so=ps_group_by_genus_ species+asc&Query=%28 Ruschia+promontorii %29) ( Fig. 8; water colour of the type collection, Fig. 9 ) .

Description:— Perennial, succulent, forming a central clump with trailing branches 20–33 cm long, internodes to 20 mm long, 2–4 mm diam., smooth, ochre, later turning light grey. Leaves trigonous, opposite, spreading, shortly fused at bases, sheath to 1 mm long, 20–25 mm long, 12 mm broad, 8–10 mm thick., without transparent line along margins, smooth and polished, light green, frequently suffused with red, acutely keeled, in side view obliquely ovate, usually recurved at the apex, margins and keel entire, cartilaginous. Flowers 1–3, 30 mm diameter, pedicels short, to 12 mm long; calyx lobes 5, unequal, acute, 7–10 mm long, 3 with membraneous edge; petals magenta, with a central darker stripe, 3-seriate, 7–11× 1–1.5 mm; filamentous staminodes white, tips yellowish, 5 mm long, papillate at bases; filaments and filamentous staminodes collected into a cone, white with yellowish tips, 3–4 mm long, papillate at bases, anthers and pollen white; stigmas 5, subulate, 2.5 mm long, top of ovary almost flat or slightly raised; nectaries a crenulate ring. Fruits 5-locular, light grey, without valve wings, top slightly raised by ± 1 mm, 6.5–7 mm diameter, base obconical, 6–7 mm long, keels brown, smooth, diverging from base, long, opening almost through 180°, covering membranes complete, with a closing rodlet below, closing bodies present, whitish, egg-shaped, largish, but not blocking the exit entirely. Seeds numerous, brown, testa cells colliculate, 1.0 × 0.8 mm.

Flowering time:— June to August.

Taxonomic notes:— Ruschia promontorii was placed in synonymy under Amphibolia laevis ( Aiton 1789: 187) H.E.K. Hartmann (2001: 38) ( Fig. 10 ) by Hartmann (1998b). This decision was based only on their similar leaf surfaces, as fruits are absent from the type specimen of R. promontorii . Our investigations of fresh fruits revealed that they are not typical of Amphibolia . In addition, the two species differ in their ecological preferences: A. laevis is restricted to gravelly or sandy areas among coastal vegetation, R. promontorii is restricted to sandstone cliffs or rocky outcrops amongst fynbos. Notably, A. laevis is absent from the Cape Peninsula and extends from Vredendal to just north of Cape Town. On account of these morphological and ecological differences, we re-instate R. promontorii and place it back in Ruschia .

Ruschia promontorii forms a compact central clump with elongated trailing or hanging branches 20–33 cm long. The leaves are rather short and thick (to 25 mm long and 8–10 mm thick), smooth, light green suffused with red, with entire margins and a prominent keel ( Fig. 9 ). Amongst the species of Ruschia that occur on the Cape Peninsula, it is similar to and may be confused easily with R. rubricaulis (Haw. 1803: 77) L.Bolus (1928: 132) , which differs in having larger leaves (2–4 cm long) with finely serrulate keels and margins and a glaucous-green colour.

History:— There is no information available about the identity of J. Rohland, who brought the plants to the National Botanical Garden in 1920, which subsequently flowered at Kirstenbosch in July 1921. The water-colour of the type collection by M. Page ( Fig. 9 ) is dated from this year, although the species was described by L. Bolus only eight years later in 1929.

Distribution and ecology:— Ruschia promontorii is endemic to the Cape Peninsula ( Fig. 5 ). It is associated with sandstone rocks among fynbos, with plants either sprawling over the rocks or hanging from ledges on cliffs ( Fig. 11 ). Collections were made at altitudes ranging from 100 to 200 m. It is locally common and roots readily when portions fall off rocks onto the soil below.

Conservation status:— Ruschia promontorii has a very narrow distribution and is currently protected within the boundaries of the Cape Point Nature Reserve. As the plants are only found on rocks or cliffs, this also protects them from fires. The species has been assessed as “Rare” by Van Jaarsveld et al. (2009).

Additional specimens examined: — SOUTH AFRICA. Western Cape, Simonstown (3418): South of Smitswinkel, just inside Cape Point Nature Reserve (- AD), 200 m, 30 July 2000, Helme 1736 ( BOL) ; Dias Point (- AD), 150 m, 26 August 1998, Desmet 1540 ( BOL) ; Cape Point , slopes below the lighthouse (- AD), 26 June 1948, Hall sub NBG s.n. ( BOL) ; Cape Point (- AD), July 1980, Manchip s.n. ( BOL) .

Ruschia vaginella Klak , nom. nov. pro Mesembryanthemum vaginatum Haworth (1821: 127) , nom. illeg. non Mesembryanthemum vaginatum Lamarck (1788: 478) ≡ Ruschia vaginata (Haw.) Schwantes (1927: 19) , comb. illeg. Type (lectotype designated by Hartmann 1999: 70): painting 1024/565 by T. Duncanson dated 03 March 1824, (K!, Fig. 12 ).

Taxonomic notes: — Chesselet & Pignal (2005: 32–33) stated that Mesembryanthemum vaginatum of Lamarck (1788: 478) belongs to the Mesembryanthemoideae . Clearly, therefore, it cannot be conspecific with M. vaginatum Haw. , which belongs to the Ruschioideae . Although M. vaginatum Haw. is poorly known, the drawing by Duncanson ( Fig. 12 ) depicts a plant with smooth leaves that are basally fused into a sheath, so that it clearly belongs in Ruschia . The name Ruschia vaginata (Haw.) Schwantes is invalid since M. vaginatum Haw. is illegitimate and so we provide a new name here for this species in Ruschia .

Figures

FIGURE 5. Distribution of Ruschia promontorii (circle) and R. turgida (square).

FIGURE 9. Ruschia promontorii, Cape Point, Western Cape, South Africa, Rohland sub NBG 1543/20 (drawing by M.M. Page).

FIGURE 10. Amphibolia laevis, Saldanha Bay, Western Cape, South Africa, Hutchinson 288 (BOL) (drawing by B.O. Carter).

FIGURE 11. Habitat of Ruschia promontorii, rocky outcrops among fynbos. Cape Point Nature Reserve, August 2006, South Africa (photo by N. Helme).

FIGURE 12. Lectotype illustration of Ruschia vaginella (drawing 1024/565 by T. Duncanson (K!).