Hesperantha palustris, 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 : 116-117

3.2. H. palustris Goldblatt & J.C. Manning , new species

Type: South Africa, Northern Cape, Calvinia (3119): Tierkloof , Bulbinella marsh on dolerite sill NW of farm houses, (− BC), 27 Sept. 2014, Goldblatt & Porter 14040 ( NBG, holo.; MO, PRE, iso.) .

Plants 350–480 mm high, evidently lacking basal sheathing cataphylls at flowering. Corm obliquely ovoid, flattened on one side in lower third, 12–14 mm diam.; tunics woody, ±black, notched below into segments. Stem suberect, simple or more usually 2- or 3-branched from near base, branches arching laxly outward. Leaves 4 or 5, mostly basal, ±linear, mostly 6–8 mm wide, soft and ±succulent, uppermost sometimes inserted shortly above ground and partly sheathing stem. Spike lax, 1- to 3-flowered, internodes 25–35 mm long; bracts green, soft to ±membranous, 12–15 mm long, inner narrower, with transparent margins. Flowers nocturnal, radially symmetric, white, middle half to two thirds of outer tepals mottled grey-brown on reverse, opening after 19:00, tepals then spreading, unscented or at most faintly scented; perianth tube ± cylindric, ± 8 mm long, reaching to ±top of bracts; tepals subequal, elliptic, 16 × 4 mm. Stamens with erect filaments ± 6 mm long; anthers held horizontally, 6–7 mm long, white, pollen white. Ovary ovoid-ellipsoid, 4–5 mm long; style dividing at mouth of perianth tube, branches ± 5 mm long, ascending, reaching to lower third of anthers in closed flower. Capsules ± ovoid-elliptic, obtuse, 12–14 × 6–7 mm. Seeds ± 2 mm long, irregularly angled by pressure, with light brown, loose testa. Flowering time: September to mid October ( Fig. 1 ).

Distribution and ecology: known only from high elevations on the Hantamsberg near Calvinia, Northern Cape ( Fig. 2 ), where it occurs in a seasonal wetland on dolerite among plants of Bulbinella nutans (Thunb.) T. Durand & Schinz ( Asphodelaceae ), which occurs in masses at the locality.

The asymmetric, obliquely ovoid corms are typical of Hesperantha sect. Concentricae ( Goldblatt, 1982) , and we suggest a likely relationship with the widespread and largely western Karoo species, H. cucullata . This is a much shorter species with firm to almost leathery, often relatively broad leaves, and white flowers with the outer tepals usually bright, glossy red on the reverse, the dark pigment usually covering almost the entire outer surface. Flowers of H. cucullata open well before sunset, mostly 16:00–16:30 ( Goldblatt et al., 2004), and produce a strong, sweet odour. The tepals are broader than in H. palustris , usually 12–16 mm long and at least a third to nearly half as wide. Capsules of H. cucullata are also usually smaller than in H. palustris , 8–10 mm long, and the globose seeds are ± 1.2 mm diam. with a smooth surface.

Conservation notes: only 16 plants of H. palustris were seen in flower but population numbers were impossible to assess due to the dense, taller surrounding vegetation. We could not determine whether more plants occurred nearby in similar habitats. The only known locality is not at present under threat.

Diagnosis: distinctive in the marshy habitat, unique for the genus, H. palustris also stands out in its tall stature, up to 480 mm high, long and soft textured leaves, and unusually lax spikes of only one to three flowers. Not unusual for western Karoo species of the genus, the flowers are white with the outer tepals reddish on reverse. In H. palustris the outer tepals are grey-brown with white edges on the reverse and the tepals are narrowly elliptic, ±16 × 4 mm, thus less than one third as wide as long. Flowers of cut stems placed in water opened after dark, ±19:00, and appeared unscented or at most weakly scented. Each flower lasted three days. The capsules are unusually large for the genus, up to 14 mm long.

Figures

Fig. 1. Hesperantha palustris, Goldblatt & Porter 14040 (NBG). A. flowering plant; B. detached flower; C. capsule.Scale bar:10 mm. Artist:J.C.Manning.

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