Rubus rigidus Smith (1819

Beek, Abraham Van De, 2021, Rubi Capenses: a further contribution to the knowledge of the genus Rubus (Rosaceae) in South Africa, Phytotaxa 515 (1), pp. 1-71 : 25-27

8. Rubus rigidus Smith (1819 : nr. 5).

Type:—Caput Bonae Spei, s. coll. (holotype LINN 653.23 [http://linnean-online. org/6372/])

Epitype (designated here):— SOUTH AFRICA. Western Cape: Grabouw, Vyeboom , along the R 321 , 28 November 2019 , Beek 2019.100 (L).

Primocane ( Figs 6A–C ) arching, diam. 5–8 mm, furrowed to obtuse angular, densely appressed stellate brownish grey hairy, with many stipitate glands; prickles unequal, 11–30 per 5 cm, declining or curved, conic, subulate or slightly compressed, longest ones up to 4–5 mm; stipules linear, 12–15 mm long, hairy and with stipitate glands. Leaves 2- jugate pinnate, with divided basal leaflets, adaxially glabrous, abaxially short white tomentose ( Fig. 6D ), with whitish grey veins; serrature fine, very sharp, unequal, double, with long (almost) straight mucros; petiole 4–6 cm, with stellate hairs and some stipitate glands, with 13–16 curved prickles; basal leaflets with 10–20 mm petiolule, pedate divided at 1–10 mm; central leaflet 60–76 mm, from attenuate or sometimes almost rounded base (ob-)ovate or elliptical, gradually attenuate into long tip, sometimes lobate, width–length index 0.55–0.69. Flowering branch ( Figs 6E–F ) furrowed, densely stellate hairy, with stipitate glands; prickles 3–6 per 5 cm, conic, subulate or slightly compressed, declining or curved, up to 2–3 mm long; stipules 9–12 mm, lanceolate. Leaves pinnate 3-foliolate or 2-jugate, apical one sometimes simple, adaxially glabrous, abaxially grey tomentose; serrature (for comparison with holotype see also Fig. 6D ) short periodical, fine, (rather) sharp; petiole 3–4 cm, hairy, with 5–11 curved prickles; central leaflet of pinnate leaves 57–67 mm long, narrow elliptic-obovate, with attenuate or rounded base, short pointed, width–length index 0.52–0.56, length of petiolule 16–26% of length of leaflet; central leaflet of 3-foliolate leaves 43–89 mm long, width–length index 0.53–0.74, length of petiolule 16–32% of length of leaflet; petiolule of basal leaflets 4–6 mm. Inflorescence ( Figs 6G–H ) narrow pyramidal or cylindric, with 2–6 axial branches, lowest with 4–20 flowers, often fasciculate, angle of basal peduncles very sharp, apical ones (almost) patent; bracts lanceolate; pedicels shorter to slightly longer than sepals, white tomentose and hairy, with some stipitate glands. Flowers: sepals ( Fig. 6I ) ovate-lanceolate, long pointed, patent, tomentose and hairy with some stipitate glands; petals pinkish red, ovate, 5–6 × 8–9 mm; stamens as long as to somewhat longer than styles, deep purple red; styles deep purple red; svaries glabrous; receptacle with some hairs. Fruit black.

Notes: — Smith (1819) gives as details for the petals: ‘The petals seem to be awl-shaped, and very small’. They are not visible on the type presently, and the word ‘seem’ indicates that Smith was not certain about their shape and size.

It was difficult to identify the type specimen with one of the taxa that presently grow in the Cape. It was even more difficult because it is only an inflorescence, and inflorescences are often very similar in different taxa and diverse within one and the same taxon. Furthermore, stipitate glands are often more abundant on the primocane than in the inflorescence, to such an extent that the inflorescences can be almost eglandular, while glands are abundant on the primocane. The type of R. rigidus has some short stipitate glands, thus both glandular and eglandular taxa were compared to check its taxonomic position.

Initially, the focus was on the direct environment of Cape Town, because the type was collected very early. However, no similar plants were found. This could be expected because most of the natural environment at the end of the eighteenth century is now within the city and likely transformed. Extension of the searched area resulted in the finding of a population of plants at Vyeboom near Grabouw, which produced a satisfactory match. This is a region where plants were collected as early as the eighteenth century [see e.g. Masson (1776); plants of his collection are in the Linnaean Herbarium, Stafleu & Cowan (1981); Ecklon & Zeyher (1836) refer to Grabouw under the old name Grietjesgat). The plants from Vyeboom have glandular primocanes and narrow leaves. Inflorescences have only a few short stipitate glands, small prickles and a similar composition as the type. A sample from this population was selected as epitype.

Ecology: —Roadsides, hedges.

Distribution: — Rubus rigidus was found on several localities between the Theewaterskloof and Grabouw on both sides of the R321, Western Cape, South Africa.

Figures

FIGURE 6. Rubus rigidus. A. Primocane with leaves. B. Primocane with leaves. C. Primocane. D. Leaf, abaxially. E. Flowering branch. F. Flowering branch. G. Inflorescence. H. Inflorescence. I. Flowers. Photographs: A. van de Beek.