Hesperantha filiformis, 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 : 117-118

3.3. H. filiformis Goldblatt & J.C. Manning , new species

Type: South Africa, Northern Cape, Calvinia (3119): Hantamsberg plateau, Farm Vanrhynshoek , in wet red clay among dolerite boulders, 1575 m, (− BD), 25 Sept. 2014, Goldblatt & Porter 14010 ( NBG, holo.) .

Plants 90–150 mm high, with short membranous sheathing cataphyll. Corm obliquely ovoid, flattened on one side in lower third, 8–10 mm diam.; tunics woody, dark brown, notched below into segments. Stem erect, simple. Leaves 3, lower 2 basal, lanceolate to falcate, up to 50 mm long, mostly 3–6 mm wide, firm, margins and main veins slightly thickened, appearing raised when dry, uppermost leaf subbasal, partly sheathing stem and free in upper half. Spike lax, 1- to 3-flowered, internodes 9–12 mm long; bracts green with membranous upper margins, outer ± 10 mm long, inner slightly shorter. Flowers nocturnal, radially symmetric, white, outer tepals mottled grey-brown along midline on reverse, opening after 19:00, tepals then spreading, sweetly scented; perianth tube cylindric, ± 12 mm long, well exserted from bracts; tepals subequal, elliptic, ±11 × 5 mm. Stamens with erect filaments ± 2 mm long; anthers held horizontally, ± 5 mm long, white, pollen white. Ovary ovoid-ellipsoid, ± 3 mm long; style dividing at mouth of perianth tube, branches ± 4 mm long, ascending, reaching to ± middle of anthers in closed flower. Capsules ± ovoid-elliptic, obtuse, ± 11 mm long. Seeds unknown. Flowering time: September ( Fig. 3 ).

Distribution and ecology: known only from the Hantamsberg plateau north of Calvinia, Northern Cape ( Fig. 2 ), in seasonally moist red clay among dolerite boulders. Plants appear numerous but are widely scattered.

Diagnosis: a small and inconspicuous species standing up to 150 mm high, H. fi liformis has lax spikes of 1 to 3 small flowers with a slender perianth tube about 12 mm long and tepals about 11 × 5 mm. Plants consistently have only three leaves, the lower two basal and the uppermost inserted in the lower third of the stem and sheathing the stem for about half its length. The firm-textured leaves are 3–5 mm wide with slightly thickened margins and main veins. The flowers are translucent white and closed during daylight hours so that only the dull grey-brown reverse of the outer tepals is visible. The flowers open after dark between 19:00 and 19:30 and then have a mild, sweet odour. Capsules of H. fi liformis are surprisingly large for so small a plant, 10–11 mm long, but mature seeds are so far unknown.

The asymmetrically ovoid corms are typical of sect. Concentricae ( Goldblatt, 1982). We considered a possible close relationship with the Hantamsberg endemic, H. hantamensis Schltr. ex R.C. Foster , but this acaulescent plant has glossy white flowers that open only during the day, with a relatively long perianth tube 14–20 mm long. It is more likely that H. fi liformis is related to the Namaqualand H. fl exuosa Klatt, which also consistently has three leaves, the uppermost partly sheathing the stem, but the somewhat fleshy leaves of this species are linear and no more than 1.5 mm wide.

Conservation notes: Population numbers are impossible to assess due to the scattered distribution but the species appeared relatively common over a wide area of several square km.

Figures

Fig. 3. Scan of type specimens of Hesperantha filiformis, Goldblatt & Porter 14010 (NBG).

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