Hesperantha eremophila, 2015

Goldblatt, P., Manning, J. C. & van Wyk, P. C. V., 2015, New species, combinations and range extensions in Hesperantha Ker Gawl. (Iridaceae: Crocoideae) from western South Africa *, South African Journal of Botany 98, pp. 114-121 : 119

3.5. H. eremophila Goldblatt & J.C. Manning , new species

Type: South Africa, Northern Cape, Vioolsdrif (2817): Richtersveld National Park, Vandersterrberg , on road to Koeskopfontein within the Venstervalle valley , ± 3 km from Koeskopfontein , (− CA), 13 Aug 2014, P. C. V. van Wyk 477 ( NBG, holo.; MO, iso) .

Plants mostly 150–350 mm high. Corm bell-shaped with flat base; tunics dark brown, softly woody, outer layers irregularly broken, margins minutely toothed. Stem unbranched. Leaves 3, lower 2 basal, falcate, blades 50–100 × 2–6 mm, bright green to slightly glaucous, with thickened, raised main vein, margins translucent-hyaline, uppermost leaf inserted shortly above ground and sheathing stem for most of its length with short blade up to 10 mm long. Spike flexuose, 1- or 2(3)-flowered; bracts ± 12 mm long, pale green flushed red to purple at tip, inner slightly shorter, with 2 green keels, narrowed distally. Flowers crepuscular, radially symmetric, white without darker colouring on reverse, dull yellow-green in throat and tube, tepals remaining cupped when fully open, with sweet, rose-like scent; perianth tube narrowly funnel-shaped, 5–6 mm long; tepals subequal, elliptic, 15–17 × 4–5 mm. Stamens with filaments ± 3 mm long, inserted ± 2 mm above base of tepals; anthers held horizontally, 7–8 mm long, pale yellow, pollen yellow. Ovary ovoid, 3–4 mm long; style dividing 2 mm below mouth of tube, branches ± 12 mm long, diverging, extending well beyond anthers. Capsules and seeds unknown. Flowering time: August ( Figs. 4–6 ).

Distribution and ecology: restricted to the slopes of the Vandersterrberg in the Richtersveld National Park, Northern Cape ( Fig. 2 ), in shaded, seasonally moist sites along seepages in rock crevices and at the foot of sandstone and conglomerate rock slabs. Plants occur in Stinkfontein Quartz Fynbos and Renosterveld (shrubland dominated by fine-leaved Asteraceae , especially Elytropappus ) and Mountain Thicket vegetation at elevations between 800 and 1300 m. Associated plants include Cheilanthes multi fi da (Sw) Sw., Spiloxene scullyi (Baker) Garside , Bulbinella gracilis Kunth , Xenoscapa fi stulosa (Spreng. ex Klatt) Goldblatt & J.C. Manning and Heliophila cornellsbergia B.J. Pienaar & A. Nicholas. Flowering appears to take place only in years with suitable rainfall. Flowers open ±14:30 at elevations above 1 200 m and ±17:30 below 1 000 m and close after midnight.

Diagnosis: the bell-shaped corm of H. eremophila conforms to sect. Hesperantha , a group of some 12 species, mostly of the western half of Western Cape but with outliers to the Kamiesberg of Namaqualand in Northern Cape and southwestern Namibia ( Goldblatt and Manning, 2007). H. eremophila has white flowers lacking dark colour on the reverse of the outer tepals and a funnel-shaped perianth tube 5–6 mm long with the tepals remaining cupped when fully open. The short tube, much shorter than the tepals, and the long style branches ± 12 mm long stand out in the section and in the genus as a whole. The flowers open in the mid to late afternoon, the timing evidently dependent on elevation and associated temperature, and close after midnight and may thus be described as crepuscular.

Among the white-flowered species of the genus, only H. dolomitica Goldblatt & J.C. Manning from southern Namaqualand has similarly cupped tepals also without colouring on the reverse of the tepals, suggesting a possible relationship with H. eremophila . Flowers of H. dolomitica are larger, with a perianth tube 12–14 mm long and tepals about as long, but much shorter style branches, ± 7 mm long, just over half as long as those of H. eremophila .

Figures

Fig. 4. Scan of type specimens of Hesperantha eremophila, Van Wyk 477 (NBG).

Fig. 5. Photograph of floral details of Hesperantha eremophila at type population. Photograph:P.Van Wyk.

Fig. 6. Photograph of plants of Hesperantha eremophila at type population.Photograph: P. Van Wyk.

Fig. 2. Distribution of Hesperantha palustris (○), H. filiformis (●), H. eremophila (Δ) and H. secunda (▲).