Keywords

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Arenifera Herre SKK 1948: 35; Hartmann 1996: 29–56; Hartmann 2001: 68–70 Typus A. pillansii (L.Bolus) Herre Etym La arena, sand, ferre, to carry, describing the fact that the leaves of the type species collect sand on their surfaces.

Shrubs to 40 cm h, lateral short shoots annulate from scars of leaves; L trigonous to triquetrous, epidermis cells lowly papillate, the outer wall with varying amounts of crystal sand inside, the stomata overarched and thus somewhat sunken; Fl in bracteolate and bracteate Inf, K 4–5, petals pink, 0–25 filamentous staminodes completely purple or white below, surrounding the stamens in a loose cone, nectary as a lophomorphic ring; Fr base funnel-shaped, the low turret-shaped top dipping from a raised outer rim into the centre, from where the persistent remains of long stigmas rise like a crown, covering membranes complete, convex, rising from a deeper centre towards the outer rim, closing rodlet broad and conspicuous, a narrow columella in the centre, valve wings broad to absent, closing body as a narrow, small hood, 6–8 locules; S elongate pear-shaped; Ecol in gravelly flats or on gentle, rocky slopes, <100 mm rainfall p.a. mainly in winter (Fig. 1); Distr NW NC and W WC, S Africa.

Fig. 1
figure 1

Distribution of Arenifera lies strictly in the winter rainfall region, not reaching the coast nor the inland March and November rainfall regime areas (Copyright H.E.K. Hartmann)

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Note: When Herre (1948: 38) described the genus with one species as new, he based his decision mainly on the higher number of locules, the covering membranes and their distal closing device, and on the central crown formed by the bases of the stigmas persisting on top of the capsule. He also suspected that the glue on the leaves of A. pillansii differed from that on leaves of Psammophora, in which genus the species had originally been placed, but this feature of a sticky surface of the leaf was not diagnostic.

Also based on the typical character states of the fruit three more species are placed in Arenifera now (Hartmann 1996). These develop spines in different ways, known also from A. pillansii. The complex has been treated under “Eberlanzia stylosa” by Hartmann & Stüber (1993) because at that time a better founded position could not be offered with good reasons.

Key to the Species of Arenifera

1.

Leaves and calyx sticky, sand adhering to the surface with age, calyx 4-lobed

A. pillansii

–

Leaves and calyx only sticky when sectioned, dark green and free of sand, calyx 5 (–6)-lobed

2

2.

Complete fruits breaking off their stalks when ripe, pedicels remaining as spines on the plants

A. spinescens

–

Fruits falling out of their bases which remain on the plants, the spines developed from pedicels with dried buds

3

3.

Spines rectangularly arranged or spreading at an obtuse angle, forming a pungent veil over the plant

A. pungens

–

Spines mostly only two below the terminal fruit, mostly spreading at an angle of c. 45°

A. stylosa

  • A. pillansii (L.Bolus) Herre SKK 1948: 35 ≡ Psammophora pillansii L.Bolus FPSA 1927: t. 280 T Pillans 5714 (BOL).

Open shrubs with occasional regeneration from the base, old leafless branches sticking out on aged plants, branchlets turning into blunt, stout spines; L shiny green at first, later brown from adhering sand grains, triquetrous, epidermis papillate and becoming warty with age by elevations above tannin idioblasts, to 25 mm l, 4–5 mm b and t; Fl ∅ 30–35, petals 35–50, pink or pink with white bases, 15–25 basally white, apically pink filamentous staminodes, 100–120 stamens with white bases and pale pink upper parts; Fr c. 15 mm l, ∅ 5–6 mm, 4–5 mm h; S 1.3–1.4 mm l, 0.65–1 mm b; Ecol in gravelly flats, <100 mm rainfall p.a. in winter; Distr N Namaqualand, NC, S Africa.

Note: The species differs from the also sand-collecting species of Psammophora in the construction of the epidermis, which here seems to develop the sticky substance inside the cuticle. The surface appears shiny early in the leaf ontogeny, but almost warty later from raised elevations. Collected sand colours the leaves brown, and with age the glue disappears gradually, not in patches as in Psammophora. No reasons to include the taxon in Psammophora can be found when growth form, leaves, the production of the sticky substance on the surface, flower structure, fruit, and seeds are compared.

A. pillansii seems to have been overlooked often in habitat due to its inconspicuous loose shrubby form. Furthermore, the plants grow dispersed in low shrubby karroid vegetation, never in conspicuous, monotypic stands. Beside the sticky leaf surface, the formation of stout spines formed by the withering upper branches of the inflorescence (not the pedicels only, as in the other species) is typical of these plants in habitat.

  • A. pungens H.E.K.Hartmann 1996: 37 T Hartmann et al. 25739 (HBG!).

Shrubs to 15 cm h, ∅ to 20 cm, covered conspicuously in spines during most of the year, the spines of subsequent nodes at angles of c. 90° to each other (Fig. 2); L dark green, triquetrous with a triangular recurved tip, epidermis with low papillae, overarching the stomata to some extent, 7–10 mm l, appressed in young state, 3–4 mm b and t; Fl buds developing completely into flowers only in the central positions of the spiny Inf, K 5, 30–40 purple petals, 3–18 purple filamentous staminodes, 70–120 stamens, stigmas 1.6–2.5 mm l; Fr ∅ 4.5–6 mm, 4–5 mm h, 6–8 locules; S smooth, c. 1.3 mm l, c. 1 mm b; Ecol in shaly flats or in loamy pockets on rocky slopes, <100 mm rainfall p.a. mainly in winter; Distr Calvinia, Namaqualand, NC, S Africa.

Fig. 2
figure 2

Arenifera pungens with the terminal capsules above fierce spines spreading mostly at right angles, always branched; note the trigonous leaves with red keels and margins (Copyright H.E.K. Hartmann)

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Note: In habitat, the stout, pungent, white spines form a conspicuous veil over each plant, but in cultivation the spines have been found to be thinner, thereby appearing more fragile; in order to retain their cushion-shape, the plants must be kept dry and very sunny.

A. spinescens (L.Bolus) H.E.K.Hartmann 1996: 38 ≡ Ruschia spinescens L.Bolus NM2 1930: 175 T Compton 19081 (BOL!).

Shrubs to 30 cm h, rarely to 40 cm ∅, spines developing only after the ripe fruits have fallen off (Fig. 3), the spiny compound Inf pushed to one side by the mostly only single ongrowing branch developing on the other side of the Inf; L trigonous, epidermis with low papillae, 10–20 mm l with a smooth basal sheath of c. 4 mm, 3–4 mm b and t; Fl in elongate Inf of several storeys, each with mostly 3-flowered dichasia, the terminal one rarely 5 Fl, K 5, petals pink to purplish-pink, few filamentous staminodes, filaments pink; Fr sometimes with very narrow valve wings, broadest in their middle, ∅ 4–6 mm, 4–6 mm h; Ecol mostly in flats, <100 mm rainfall p.a. in winter or in March and November; Distr Clanwilliam, Laingsburg, Vanrhynsdorp, WC, S Africa.

Fig. 3
figure 3

Arenifera spinescens bearing capsules in small infructescences, branching alway at angles of 45° or less, resulting in a slender growth form (Copyright H.E.K. Hartmann)

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Note: The species has probably been confused with Ruschia spinosa occurring in part of the area; the latter develops very sharp spines from pedicels and their withering buds only, whereas the spines of A. spinescens are blunt since they are derived from pedicels after having lost their ripe fruits.

A. stylosa (L.Bolus) H.E.K.Hartmann 1996: 38 ≡ Ruschia stylosa L.Bolus NM1 1928: 144 ≡ Eberlanzia stylosa (L.Bolus) L.Bolus NM3 1958: 387 ≡ M. styliferum (L.Bolus) N.E.Br. GC 1930: 32 T Pillans 5742 (BOL) = Ruschia armata L.Bolus NM1 1928: 145 ≡ M. armatum N.E.Br. GC 1930: 32 ≡ Eberlanzia armata (L.Bolus) L.Bolus NM3 1958: 387 T Pillans 5789 (BOL).

Shrubs to 25 cm h, ∅ to 40 cm; L trigonous, almost smooth, 15–25 mm l with a sheath of c. 5 mm, 4–5 mm b; Fl developing only on the central pedicels, buds on the distal branches of the Inf turning into spines by shrinking, rich Inf rare, spines at an angle of 45° to the main pedicel or peduncle (Fig. 4), K 4–5, petals pink to purplish pink, very few to no filamentous staminodes; Fr stalks and base papillate, valve wings absent, 6–8 locules; Ecol in loamy pockets of gentle slopes with rocks, <100 mm rainfall p.a. in winter; Distr N Namaqualand, NC, S Africa.

Fig. 4
figure 4

Arenifera stylosa bearing a terminal fruit above spreading branched spines, angles near 45°; note the less prominently keeled leaves (Copyright H.E.K. Hartmann)

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Note: A. stylosa occurs in the same area as A. pillansii, but higher up on the more rocky slopes and never in close association with the latter.