Heliophila volkii Al-Shehbaz, 2020

Al-Shehbaz, Ihsan A., 2020, Ten new species in the southern African genus Heliophila (Brassicaceae; Cruciferae), Phytotaxa 434 (1), pp. 65-88 : 83-85

Heliophila volkii Al-Shehbaz , sp. nov.

Diagnosis:— Heliophila volkii is readily distinguished by being a shrub with fascicled, terete, fleshy leaves adaxially grooved by involute margin, unappendaged petals and stamens, and prominently veined oblong-lanceolate to narrowly lanceolate fruit.

Type:— SOUTH AFRICA. Western Cape, Central Karoo District, Prince Albert, Droekloof Mts. , summit crest and kranzes on S side in shade, very rare hanging from cracks in rocks, 28 Aug. 1988, J. H. J. Volk s.n. (holotype, BOL-109380; isotype, MO-3760135). Figure 10 .

Description: —Plants subshrubs, glabrous, not glaucous. Trichomes absent. Stems woody, 20–30 cm tall, current-year growth longitudinally striate-muricate with cartilaginous papillae to 0.05 mm high and to 0.1 mm wide, terete, erect to ascending, many branched throughout. Leaves cauline, usually fascicled on short lateral shoots, somewhat fleshy, terete, drying thick, 1-grooved adaxially by involute leaf margins; petiole absent; blade simple, acicular, 1–4 cm × 0.5–1 mm, sessile, not auriculate at base, with a pair of stipule-like glands at node, glabrous, apex apiculate, base not decurrent, articulate. Racemes terminal, corymbose, 6–10-flowered, elongated in fruit, not secund; rachis straight, striate as stem; fruiting pedicels with a pair of basal, bract-like minute glands, articulate at base, glabrous, slender, ascending to divaricate, persistent, lowermost 4–11(–17) mm long; buds oblong. Sepals ascending, oblong, 5–6 mm long, glabrous, caducous, lateral pair not cucullate at apex, slightly saccate at base, median pair slightly cucullate, not saccate. Petals white?, oblanceolate, 10–12 × 3–4 mm, ascending, obtuse at apex, unappendaged, not papillate; claw hardly differentiated from blade, ca. 1 mm long. Stamens slightly tetradynamous; filaments 4–5 mm long, glabrous, unappendaged; anthers oblong, 1.3–1.5 mm long, not apiculate at apex. Nectar glands lateral, median glands absent. Ovary glabrous; ovules 4–8 per ovary. Fruit dehiscent silique, capsular, narrowly oblong-lanceolate to narrowly lanceolate, 1–2.5 cm × 3–4 mm, latiseptate, glabrous, not moniliform straight along replum, slightly torulose or not, erect to ascending, apex cuneate into style; valves papery, midvein and lateral veins prominent, margin not thickened; gynophore 0.5–1.5 mm long; style in fruit 3–5 mm long, cylindrical, slender, glabrous; stigma entire. Seeds uniseriate, ovate-suborbicular, flattened, wingless, not margined, 3–4 × 2.5–3 mm, sinus wide, shallow.

Phenology: —Flowering in May.

Distribution: —Endemic to Droekloof Mts. in Prince Albert Municipality, Central Karoo District.

Etymology: —Named after the South African botanist J. H. J. Volk who gathered three of the four known collections of the species.

Additional specimens examined (Paratypes): — SOUTH AFRICA. Western Cape, Central Karoo District, Prince Albert, Klaarstroom , on crest of Droekloof Mts. , 3900 ft [ca. 1188 m], 28 Aug. 1988, J. H. J. Volk 2011 ( BOL, PRE) ; Top of Droekloof Mts, near Klassrstroom , 3900 ft, 5 Nov. 1986, J. H. J. Volk 1690 ( BOL, PRE) ; Sand River Mts , May 1907, R. Marloth 4482 ( PRE) .

Habitat: —Arid fynbos, hanging from cracks in rocks in shady areas, moist rocky loam in shade of large boulders.

Discussion: — Heliophila volkii is most closely related to H. brachycarpa Meisner (1842: 465) sensu Al-Shehbaz (2019) , not Marais (1970), which it closely resembles, especially in floral morphology, ovule number per ovary, prominently veined fruit valves, and styles distinctly delimited from and not attenuate with fruit apex. Marais, who never examined the type collection of H. brachycarpa , erroneously based the circumscription of the species on plants that correspond perfectly well with the type collection of H. florulenta Sonder (1846: 263) . The last species characteristically differs from H. brachycarpa by having papillate (vs. glabrous) petal claws and staminal filaments, as well as in fruit apex attenuate into (vs. clearly delimited from) styles (0.7–)1–2(–2.7) mm (vs. (4–) 5–10 mm) long.

Heliophila volkii is readily distinguished from H. brachycarpa by being subshrubs 20–30 cm tall and by having stems longitudinally striate-muricate with cartilaginous papillae, acicular leaves usually fascicled on short lateral shoots and 1-grooved adaxially by involute leaf margins, basally articulate pedicels and leaves, narrowly lanceolate to narrowly oblong-lanceolate fruit 3–4 mm wide, and styles 3–5 mm long. By contrast, plants of H. brachycarpa are scrambling shrubs or small trees 1–2 m tall that have stems lacking the muricate cartilaginous papillae, leaves always flat and not fascicled, non-articulate pedicels and leaves, broadly lanceolate fruit (6–) 7– 9 mm wide, and styles (4–) 5–10 mm long.

Except for one collection, Marloth 4482 (PRE), which was made in May 1907, all other collections of Heliophila volkii that I examined were made in 1986 and 1988 by J. Volk and were in fruit. Marais examined the above sheet and annotated it on 10 Feb 1965 and cited it ( Marais 1970: 73) as “…possibly a new species allied to H. scoparia and H. cedarbergenis .” In my opinion this novelty is not closely related to this species pair, though it falls with them in the same group that share the woody habit, paired glands at the bases of pedicels and leaves, latiseptate silique fruit, and distinct styles.

Figures

FIGURE 10. Heliophila volkii. A. Plant. B. Portion of young stem. C. Leaf. D. Fruit and fruiting pedicel. Drawn by Al-Shehbaz from isotype (MO-3760135).