Senecio paludosus Linnaeus (1753: 870)

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

10. Senecio paludosus Linnaeus (1753: 870) . Solidago serratifolia Gilibert (1782: 202) , nom. inval. ( McNeill et al. 2012, ICN Appendix VI Opera Utique Oppressa). Jacobaea paludosa (Linnaeus) Gaertner, Meyer & Scherbius (1801: 211) . Cineraria serratifolia Gray (1821: 469) , nom. illeg. superfl. ( McNeill et al. 2012, ICN Art. 52.1). Doria paludosa (Linnaeus) Fourreau (1868: 404) . Senecio paludosus var. typicus Rouy (1903: 325) , nom. inval. ( McNeill et al. 2012, ICN Art. 24.3). TYPE: Sweden, Scania, sine collector (lectotype, designated by Kadereit (1998: 366), LINN 996.57 image!).

Perennial herb. Rhizome up to 10 cm long, 0.4–0.8 cm in diam., ± horizontal, with swelled fastigiate roots. Stem 58–180 cm, erect, densely leaved, corrugated, fistulous, not ramificated, glabrous to weakly lanate, base without remnants of old leaves or tufts of hairs. Basal leaves absent. Cauline leaves numerous (16–60), the lower ones withering early, ± discolorous; middle cauline leaves 6.8–21 cm long, 0.5–4.4 cm wide, alternate, narrowly lanceolate to lanceolate (ratio middle leaf width / middle leaf length = 0.05–0.27), acute, sessile to subsessile, rarely attenuated into a petiole up to 1 cm long, serrate to dentate (teeth 0.5–5.7 mm deep), glabrescent to floccose above, glabrescent to lanate beneath, tertiary venation inconspicuous; upper cauline leaves 1–14.4 cm long, 0.1–1.5 cm wide, narrowly lanceolate to lanceolate (ratio upper leaf width / upper leaf length = 0.04–0.50), acute, sessile, rarely attenuated into a petiole up to 1 cm long, serrate to subentire (teeth 0.3–1.9 mm deep), glabrescent to floccose above, glabrescent to lanate beneath, rarely glabrescent. Synflorescence 5–33 cm long, corymbose to subcorymbose, with lanceolate-oblong bracts. Capitula (5–)9–25(–150), 23.2–42.4 mm in diam.; involucre 9.7–16.5 mm in diam., 5–8 mm long, bell-shaped to obconical; involucral bracts (16–)20–22(–26), 4–6.8 mm long, 0.7–1.6 mm wide, with scarious margin 0.2–0.5 mm wide, lanceolate, acute, smooth, apex sometimes with a faint black spot, glabrescent to lanate; supplementary bracts (5–)9–13(–17), 2–6.9 mm long, 0.2–0.7 mm wide, subulate, without scarious margin, a third to two thirds as long as involucral bracts, glabrescent to lanate, not imbricated. Ligulate florets 13–24, 10.5–23.1 mm long, yellow; tubular florets 5–8 mm long, 0.4–1.3 mm in diam., yellow. Achenes 2.4–4.9 mm long, 0.5–0.8 mm wide, subcylindrical (ratio achene width / achene length = 0.11–0.28), shorter than pappus (ratio achene length / pappus length = 0.38–0.68), with 7–14 ribs, glabrous to covered with scattered trichomes 0.1–0.2 mm long over the whole surface; pappus 4.9–8.6 mm long, whitish.

SYSTEMATICS OF SENECIO SECTION CROCISERIS

Phytotaxa 211 (1) © 2015 Magnolia Press • 41

Etymology: — The epithet paludosus refers to marshes, the habitat where this species usually grows.

Discussion: — Senecio paludosus is a distinctive species with numerous cauline leaves, sessile to subsessile, dentate, and not abruptly decreasing in size up the stem. The fistulous stem and the corymbose synflorescence with numerous and small capitula are other diagnostic characters. In some cases it was confused with S. nemorensis Linnaeus (1753: 870) (or related species), which belongs to Senecio sect. Doria . However, they may be easily differentiated by the number of ligulate florets: 13–24 in S. paludosus vs. 1–8 in S. gr. nemorensis ( Chater & Walters 1976) . It is a variable species regarding the indumentum of its leaves and achenes, the characters that hold the two subspecies here recognized.