Achyranthemum argenteum N. G. Bergh 2019, comb. nov.
Creators: name: Bergh, N. G.
name: Manning, J. C.
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Asterales
Asteraceae
Achyranthemum
Achyranthemum argenteum

description: 4.4. Achyranthemum argenteum (Thunb.) N.G.Bergh, comb. nov.
Xeranthemum argenteum Thunb., Prodr. Pl. Cap. 2: 152 (1800). Helichrysum (as ‘Elichrysum’) argenteum (Thunb.) Willd., Sp. Pl., ed. 4, 3 (3): 1906 (1803). Syncarpha argentea (Thunb.) B.Nord. in Comp. Newsl. 17: 6 (1989).
Type: South Africa, Eastern Cape, ‘e Cap. b. Spei’, Thunberg s.n. (UPS-THUNB 19297, holo!)
Low, tangled shrublet, height unknown, branches woody, nodes relatively widely spaced, stems below synflorescences densely leafy, stems with a fine, silver-grey appressed woolly indumentum of slender hairs. Leaves imbricate, narrowly oblanceolate with a distinctly narrowed base, basally somewhat decurrent, lamina flat or conduplicate, recurved at least at the apex, mid-rib somewhat depressed adaxially but prominent abaxially, several smaller lateral veins also abaxially prominent, parallel to the midvein in the narrowed basal portion of the leaf, running outwards away from the midvein in the broader distal leaf lamina, leaf 12–30 mm long × 2.0–8.0 mm wide, apex narrowed to a blunt, strongly recurved point that twists to one side, leaf thin, both surfaces lanate with long (1–2 mm or longer), fine, pale silvery-grey arachnoid hairs cohering to form a thin but dense, tightly appressed antrorsely oriented irregularly reticulating indumentum. Capitula terminal, rarely solitary, usually in corymbs comprising 2 to 3(–6) capitula, depressed-globose, 12–18 mm long and (10–)12–15(–18) mm wide, pedunculate, peduncles 3–60 mm long, densely pale-grey felted with a few small lanceolate bracteoles; involucral bracts white becoming cream-coloured with age, ±90, in ±8–10 series, few outermost erect, broadly lanceolate, 7 × 3 mm, lamina white, smooth, middle series erect to spreading, linear-lanceolate to narrowly oblanceolate, 12 × 3 mm, stereome ± 2 mm long, few bracts in innermost series, linear, 7–9 × 2 mm, stereome 6–8 mm long, lamina very short with obtuse apex. Receptacle ± 7 mm in diameter. Florets ± (75–)85–120(–150), corolla yellow, 4.5–6.0 × 0.7 mm, lobes acuminate; anther apical appendage caudiculate. Cypselae ovoid, 1.2 × 0.8 mm, dark reddish-brown. Pappus bristles united at the base into a smooth ring, scabrid with very slender, regular barbs that are longer and more sparsely and irregularly arranged towards the apex, apices slender, acute. Flowering time: September– November (Fig. 6).
Distribution and ecology: Restricted to sandy seaside habitats mostly in the Eastern Cape, from near the Storms River mouth in the west to the mouth of the Fish River in the east (Fig. 6).
Diagnosis: Achyranthemum argenteum grows in coastal dune habitats and has soft leaves with a very fine, silvery indumentum and large heads with usually>80 florets, with white or cream involucral bracts. It has in the past been confused with A. af fi ne, but that species has involucres white flushed dark pink (see further discussion under A. af fi ne); also, A. af fi ne always has fewer than 80 florets in a capitulum. Achyranthemum argenteum can also be confused with A. sordescens, from which it is distinguished by its much larger, paler capitula and by the thinner, smoother leaf indumentum. The indumentum is very thin and held tight to the leaf surface in A. argenteum, so that the shapes of the leaf veins can be discerned. In contrast, the veins are obscured in A. sordescens by the thicker tangled indumentum.
The large capitula with white bracts and the leaf indumentum recall the distantly related Syncarpha argyropsis, another coastal species, but A. argenteum has leaves that are smaller and distinctly recurved at the tip, smaller heads (12–18 × 10–18 mm in A. argenteum vs. 15–20 × 18–24 mm in S. argyropsis) and pappus bristles that are scabrid versus distinctly plumose in S. argyropsis. In addition, S. argyropsis has fenestrated stereomes on the involucral bracts (Hilliard and Burtt, 1981b), while the stereome is undivided in A. argenteum (as in all other Achyranthemum and Syncarpha species).
Conservation status: The conservation status of this species is not known, since the last conservation assessment treated the taxon Syncarpha argentea, which included plants now segregated as A. af fi ne. The present concept of Achyranthemum argenteum is likely to be of greater conservation concern, having a smaller range and fewer populations, and requires re-assessment.
History: Xeranthemum argenteum was described by Thunberg in 1800 based on a plant he collected during his time at the Cape, most likely between 1772 and 1774, when he is known to have spent time on the Eastern Cape coast (Glen and Germishuizen, 2010).
Additional specimens seen: South Africa. Eastern Cape. –3325 (Port Elizabeth): Uitenhage Div., van Stadens, (– CC), 14 Sept 1930, Holland PRE 51,884 (PRE); 5.5 miles NE of Sea View (– CD), 30 Nov 1960, Acocks 21,702 (PRE); Cape rd. 10th Mile Port Elizabeth (– CD), 7 Aug 1932, Long 697 (PRE); Emerald Hill near Port Elizabeth (– DC), Jan 1886, Bolus s.n. BOL (BOL 46522); Port Elizabeth (– DC), 10 Jan 1949, Theron 573 (PRE). – 3326 (Grahamstown): Woody Cape, slack of high dunes (– CD), 5 Nov 1985, Jacot Guillarmod 9816 (PRE); Bathurst Dist., Kasouga mouth, beach (– DA), 21 Sep 1920, Britten 2294 (PRE); ± 500 m west of Bushmans' River mouth behind first row of dunes, on dune slack (– DA), 12 Mar 2011, Haiden 1 (NBG); 500 m west Bushmans' Rivermouth behind first row of dunes, on dune slack (– DA), 12 Mar 2011, Haiden 2 (NBG); Alexandria Dist., Bushman’ s river mouth, west bank (– DA), 28 Sep 1951, Archibald 3689 (PRE); Bathurst Dist., Bushmans River (– DA), 1 Jan 1936, Dyer 3360B (PRE); ‘ ad nivellam maris ord. fl. Kasouga’ (– DA), MacOwan 1439 (SAM 38125); Bathurst Div., Port Alfred (– DB), Oct 1923, Rogers 28,019 (PRE); Bathurst Div., near sea at Port Alfred (– DB), Sep 1915, Tyson 13,421 (PRE); Albany Div., Kowie West (– DB), Sep 1915, Tyson 13,298 (BOL); Kowie West (– DB), Sep 1916, Tyson 17,220 (PRE). – 3327 (East London): ‘ In arenosis littoris pr. ost. fl. Vischriver’, ‘ad nivellam maris ord. fl. Kasouga’ (– BC), MacOwan 1439 (PRE 0204248 /02994, SAM 38125); Bathurst Dist., Three Sisters, (– CA), 25 Sep 1918, Britten 831 (PRE). – 3423 (Knysna): Plettenberg Bay, just west of Beacon Island Hotel, sand dunes near sea, (– AB), 29 Jun 1978 (herbarium specimen taken ex. hort. 17 Nov 1982), van Jaarsveld E. 3276 (NBG). – 3424 (Humansdorp): Witte Els Bosch, coast slopes, Oct 1920, (– AA), Fourcade 950 (BOL, NBG); Oudebos Strand, 3 Oct 1963, (– AA), Levyns 11,471 (BOL); Eerste River, along the coast (– AB), 20 Sep 1954, Esterhuysen 25,684 (BOL); Oyster Bay, coastal garden in town (– BA), 15 Nov 2013, Bergh 2289 (NBG); Kromme Bay (– BB), 10 Sep 1960, Acocks 21,456 (PRE); Jeffreys Bay, Tokio Sexwale Township, coastal dune, (– BA), 15 Apr 2000, Brand 185 (PRE). – 3425 (Humansdorp): W of Port Elizabeth, Skoenmakerskop, dunes behind first row of houses (– BA), 7 Sep 2002, Koekemoer 2341 (PRE); Cape Recife, on dunes along beach, (– BA), 12 Sep 1977, Olivier 1845 (PRE); Sardinia Bay Reserve, Cape Recife, Marine D., (– BA), Aug-Sep, Vanderplank s.n. (GRA 0054515). – Without precise locality: Eastern Province, Bowker 209 (BOL, PRE 1296, SAM 17894). 1832, Burchell 3736/G00470256 (G-DC [digital image]); ‘in arenosis lapidosis prope Clanwilliam’ (doubtful locality), MacOwan 3292 (SAM); collector unknown (SAM 17894); Curator Pretoria Bot. Gard. 1296 (PRE 204240).
description: Published as part of Bergh, N. G. & Manning, J. C., 2019, Achyranthemum N. G. Bergh, a new genus segregated from Syncarpha DC. (Asteraceae, Gnaphalieae) *, pp. 434-456 in South African Journal of Botany 125 on page 448, DOI: 10.1016/j.sajb.2019.08.015, http://zenodo.org/record/10496693