Heliophila biseriata 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 : 68-70

Heliophila biseriata Al-Shehbaz , sp. nov.

Diagnosis:— Heliophila biseriata is readily distinguished from its nearest relatives by having biseriate seeds, strongly latiseptate, oblong fruits 1.3–2 cm × (3–) 4–5 mm, and pinnatisect 3–5-lobed leaves, and by the lack of indumentum and paired glands at the bases of petioles and fruiting pedicels.

Type:— SOUTH AFRICA. [Northern Cape, Namakwa, Hantam], 27 miles S by W of Brandvlei, arid karoo desert, 3100 ft [ca. 944 m], 22 June 1948, J. P. H. Acocks 14421 (holotype, PRE). Figure 2 .

Description: —Plants annual herbs, not glaucous. Trichomes absent. Stems herbaceous, 5–25 cm tall, smooth, terete, decumbent, 3–14 from base, glabrous throughout. Basal and lowermost cauline leaves fleshy; petiole 5–12 mm long; blade pinnatisect, 3–5-lobed; lateral lobes linear, 0.6–2 cm × 0.5–1 mm, terete, not auriculate at base, without a pair of stipule-like glands at node, glabrous, base not decurrent or articulate. Racemes terminal, lax, 8–16-flowered, elongated in fruit, not secund; rachis straight, glabrous; fruiting pedicels without a pair of basal bract-like glands, not articulate at base, glabrous all around, slender, gently recurved or rarely divaricate, curved or rarely straight, persistent, lowermost 1–2 cm long; buds oblong. Sepals ascending, oblong, 4–5 mm long, glabrous, caducous, not cucullate at apex, not or slightly saccate at base. Petals white, broadly obovate, 5–7 × 4–6 mm, ascending, rounded at apex, unappendaged, not papillate; claw absent. Stamens slightly tetradynamous; filaments 2.5–3.5 mm long, glabrous, unappendaged above base; anthers oblong, 1.2–1.5 mm long, not apiculate at apex. Nectar glands lateral, lunar, median glands absent. Ovary glabrous; ovules (34–)48–60 per ovary. Fruit dehiscent silique, capsular, oblong or narrowly so, 1.3–2 cm × (3–) 4–5 mm, strongly latiseptate, glabrous, not moniliform, straight along replum, obscurely torulose to smooth, usually reflexed; valves papery, midvein distinct, lateral veins obscure, margin not thickened; gynophore obsolete to 0.3 mm long; style in fruit 0.9–1.5 mm long, cylindrical, slender, slightly stout, glabrous; stigma entire. Seeds biseriate, orbicular or nearly so, flattened, winged, 1.6–2 mm in diam.; wing 0.08–0.2 mm wide, sinus wide.

Phenology: —flowering late June through July and September into October.

Distribution: —southern Northern Cape and adjacent northeastern Western Cape.

Etymology: —the species epithet is derived from the biseriate seed arrangement per locule.

Additional specimens examined (Paratypes): — SOUTH AFRICA. Northern Cape, [Namakwa, Hantam], Brandvlei to Loeriesfontein , 2 km SE of Lekkeroog, sandy clay flats, 11 July 1986, E. G. H. Oliver 8832 ( PRE) ; 13.5 km N from N27 to Brandvlei, M. Lysák & T. Mandáková 220808/18 ( MO) ; Farm Uitkoms, Calvinia-Middelpos road, 1100 m, 3 Sep. 1986, Burger & Louw 207 ( PRE). [Namakwa, Karoo Hoogland], outside of Williston, 20 July 1967, H. P. van der Schijff 7050 ( A, PRE). [Pixley ka Seme, Ubuntu], Richmond, 26 km N by W of Merriman Street , 1250 m, 7 Oct. 1970, J. P. H. Acocks 24428 ( K) ; Richmond , 4500ft [1372 m], July 1923, Gill 62 ( PRE) . Western Cape, Beaufort West, Ratelfontein , 1219 m, 12 Sept 1986, D. A. M. B. Shearing 1325 ( PRE) .

Habitat: —sandy clay or sandy loam, sandy slopes, arid Karoo desert; 940–1370 m.

Discussion: — Marais (1970: 33) was the first to suspect that this species of Heliophila may represent a novelty by indicating that “ Acocks 14421 from Calvinia and Gill 62 from Richmond district are closely related to H. seselifolia , but are distinguished by their 3.5–4.8 mm broad fruits with seeds in 2 rows, 1.9–2 mm in diameter; the ovules vary from 36–48. Having the seeds in 2 distinct rows is not very common in Heliophila , and I hesitate to name these plants until more material becomes available.” With these substantial differences between the two species, it is surprising that he did describe the above two collections as new. In fact, Acocks 14421 is selected herein as the holotypes because it is more complete than the other paratypes cited above.

Heliophila biseriata resembles H. seselifolia Burch ex Candolle (1821b: 684) in being glabrous annuals with pinnatisect leaves, in lacking the paired glands at the leaf and pedicel bases, and in having flattened, non-moniliform, usually pendent fruits with flattened suborbicular to orbicular seeds. However, from the latter the novelty differs significantly by having oblong (vs. linear to linear-oblong) fruits (3–)4–5 (vs.1.5–3) mm wide, biseriate and winged (vs. uniseriate and wingless) seeds, (34–)48–60 (vs. 12–24(–26)) ovules per ovary, unappendaged (vs. usually appendaged) filament or petal bases, smaller petals (5–7 vs. 6–10 mm long), and nonfleshy (vs. fleshy) 3- or 5-lobed (vs. 3–)5– 11(–13)-lobed) pinnatisect leaves. Although the ranges of both species occupy generally broad areas of the southern Northern Cape, no morphological intermediates have been found.

Biseriate seeds are extremely rare in Heliophila , and they are sometimes found in some plants of the unrelated H. minima ( Stephens 1912: 35) Marais (1964: 166) and, therefore, such seed arrangement evolved independently in these species. Heliophila biseriata is easily distinguished from H. minima by being glabrous, decumbent annuals (vs. puberulent, erect or ascending perennials or rarely annuals), with petiolate (vs. sessile) pinnatisect (vs. undivided or apically 2- or 3-fid) lowermost leaves, leaf and pedicel bases without (vs. with) paired basal glands, smaller petals (5–7 vs. 6.5–10 mm long), oblong (vs. linear) fruits 1.3–2 (vs. (3–)3.5–8.2(–8.8)) cm long, shorter styles (0.9–1.5 vs. (1–)2–5(–7) mm long, and winged (vs. narrowly margined) seeds.

One collection of Heliophila biseriata ( van der Schijff 7050) erroneously recorded the plants as shrubs with yellow flowers. Despite the availability of only nine specimens for this study, the species is variable in the ovule/seed number per ovary/fruit, and Acocks 14421 and 24428 have the highest (60) and lowest (34) numbers, respectively. Furthermore, the holotype has the smallest petals (ca. 5 × 4 mm) compared to Oliver 8832 and Shearing 1325 (all in PRE) with petals ca. 7 × 6 mm.

Figures

FIGURE 2. Heliophila biseriata. A. Plant. B. Basal leaf. C. Petal. D. Fruit and fruiting pedicel. E. Seed. Drawn by Al-Shehbaz:A, B, D–E from holotype (PRE), C from Oliver 8832 (PRE)