Senecio racemosus (Bieberstein) Candolle (1838a: 358)

Calvo, Joel, Álvarez, Inés & Aedo, Carlos, 2015, Systematics of Senecio section Crociseris (Compositae, Senecioneae), Phytotaxa 211 (1), pp. 448-450 : 448-450

Phytotaxa 211 (1) © 2015 Magnolia Press • 69 21. Senecio racemosus (Bieberstein) Candolle (1838a: 358) . Cineraria racemosa Bieberstein (1798: 119) . Cineraria caspica Persoon (1807: 439) , nom. illeg. superfl. ( McNeill et al. 2012, ICN Art. 52.1). Senecio caspicus (Persoon) Lessing (1834: 170 , 193), nom. illeg. superfl. ( McNeill et al. 2012, ICN Art. 52.1). Senecio racemosus var. puberus Candolle (1838a: 358) , nom. inval. ( McNeill et al. 2012, ICN Art. 26.2). Branicia insignis Andrzejowski ex Trautvetter (1883: 476) , nom. illeg. superfl. ( McNeill et al. 2012, ICN Art. 52.1). Jacobaea racemosa (Bieberstein) Pelser in Calvo et al. (2013: 137). TYPE: Azerbaijan, Xizi, Altiaghach, ex montibus Schirvanicis, [40º52'N 48º58'E], 1796, F.A.M. Bieberstein s.n. (lectotype, designated by Menitsky & Konechnaya (2001: 95), LE!).

Perennial herb. Rhizome 3.4–6 cm long, 0.7–1 cm in diam., ± horizontal, with swelled fastigiate roots. Stem 32–94 cm, erect, leaved, corrugated, solid, not ramificated, glabrescent to weakly arachnoid, base with fibrous remnants of old leaves and without tufts of hairs, sometimes violet coloured. Basal leaves 7–25 cm long, 1.9–5.2 cm wide, persistent, sometimes withering early, elliptic to oblanceolate (ratio basal leaf width / basal leaf length = 0.15–0.45), obtuse to acute, attenuate to cuneate, with a petiole 2.5–17.5 cm long, irregularly dentate (teeth 0.6–2.4 mm deep, increasing in size towards base), rarely subentire, glabrescent above and covered with scattered trichomes beneath (trichomes 0.1–0.9 mm long), concolorous. Cauline leaves 4–18; middle cauline leaves 4.2–19.6 cm long, 0.6–5.2 cm wide, alternate, lanceolate to oblanceolate (ratio middle leaf width / middle leaf length = 0.05–0.31), acute to obtuse, semi-amplexicaul auriculate to sessile, rarely attenuated into a petiole up to 5.5 cm long, dentate (teeth 0.5–4.7 mm deep), glabrescent to covered with scattered trichomes (trichomes 0.2–1 mm long), tertiary venation sometimes slightly marked; upper cauline leaves 1.2–15.5 cm long, 0.2–2.4 cm wide, lanceolate (ratio upper leaf width / upper leaf length = 0.09–0.42), acute, semi-amplexicaul auriculate, subentire to dentate (teeth 0.4–2 mm deep), glabrescent to covered with scattered trichomes. Synflorescence 7.5–50 cm long, racemose to narrowly paniculate, with oblong-lanceolate bracts, often auriculate. Capitula (7–)10–24(–77), 24.4–46.2 mm in diam.; involucre 10.4–25 mm in diam., 9–14 mm long, obconical; involucral bracts (10–)12–13(–18), 6.9–11 mm long, 2–4 mm wide, with scarious margin 0.4–1.2 mm wide, sometimes slightly fimbriate, lanceolate to oblong, attenuate, weakly 1–3-keeled, apex often with a black spot, glabrescent to weakly arachnoid near the base (trichomes 0.2–0.4 mm long); supplementary bracts (5–)8–10(–12), 3.2–7.7 mm long, 0.6–1.3 mm wide, subulate, without scarious margin, a third to three quarters as long as involucral bracts, glabrescent to weakly arachnoid (trichomes 0.3–0.6 mm long), not imbricated. Ligulate florets 7–13, 14–22.1 mm long, yellow; tubular florets 6–8.9 mm long, 0.8–2.1 mm in diam., yellow. Achenes 3.4–6.2 mm long, 0.8–1.4 mm wide, subcylindrical (ratio achene width / achene length = 0.17–0.28), shorter than pappus (ratio achene length / pappus length = 0.47–0.9), with 9–12 ribs, glabrous to covered with trichomes along ribs 0.1–0.4 mm long; pappus 5–9 mm long, whitish.

Etymology: — The epithet racemosus refers to the synflorescence architecture.

Discussion: — Senecio racemosus is readily distinguishable for displaying a racemose to racemose-paniculate synflorescence, semiamplexicaul cauline leaves, and the stem base covered with brown fibrous remnants of old leaves. It is variable in capitula number, leaf indumentum, and achene indumentum. This last character allows recognition of the two subspecies in the present treatment.

This species may be confused with S. buschianus because both species have a similar habit, obconical involucre, and fibrous remnants of old leaves at the stem base. The characters to differentiate each other are the number of capitula (lower in S. buschianus ), the indumentum of involucre (glabrescent to weakly arachnoid near the base in S. racemosus vs. tomentose to arachnoid, denser towards the base in S. buschianus ), and the synflorescence architecture (racemose to racemose-paniculate in S. racemosus vs. corymbose to pseudoracemose in S. buschianus ). Their ranges of distribution do not strictly overlap, but both species grow in northeastern Azerbaijan, where S. racemosus subsp. racemosus is scarce.