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1. Helosciadium inundatum (L.) W.D.J. Koch map
Koch, Gen. pl. Umbell.: 126 (1824). – Sison inundatum L., Sp. pl.: 253 (1753). – Apium inundatum (L.) Rchb. f. (1863). – Type: Linnaean Herbarium 356.7, right-hand specimen (LINN) lectotype, sel. by Reduron, Nordic J. Bot. 22: 85 (2002).
D Svømmende Sumpskærm. N krypselleri. S krypfloka.
Literature. Lindblad & Ståhl 1989, Mossberg et al. 2003 (ill.).
Helophyte or hydrophyte. Heterophyllous perennial, tiny (when helophytic) or elongated to more than 1 m (when hydrophytic). Stem widely hollow and easily compressed, terete with elevated veins, green or sometimes violet, with a creeping basal part, sometimes rooting at nodes; when growing in water with a 1.5–3.5 mm thick submerged part having 1–7 finely divided leaves, and a 4–11(–27) cm tall, 1–2.4 mm thick aerial part having 2–6 ± broad-lobed leaves. Narrow-lobed leaves 3–4-pinnatifid, with 7–9 pairs of lobes; sheath 0.7–1.3(–1.9) cm, reaching the blade; blade 2–5(–6) × 1.2–3.5(–6.5) cm, with a length/width ratio of 0.9–2(–2.8). Broad-lobed leaves 1-pinnate; sheath distinct, 0.5–1.1(–1.3) cm, not purplish, distinctly membrane-bordered; petiole 0.7–2.1(–3.5) cm; blade 0.9–2.4(–3.1) × 0.8–2.3 cm (length/width ratio 0.8–1.6). Leaflets 1–3 pairs, sessile; angle leaflet/rachis 55–80°. Apical leaflet 1–2-pinnatifid, with (1–)2 pairs of primary lobes, petiolule 2–6(–10) mm; blade 5–9(–13) × 6–11(–13) mm (length/width ratio 0.7–1); base cuneate to truncate; margin not papillose, with cuspidate or sometimes acuminate, usually purplish-tipped teeth; apical lobe usually obtuse, 1–2.6(–4) × 1–1.6(–2.3) mm, with a length/width ratio of 0.8–1.7(–2.3).
[2n=22]
Umbels reduced, opposite the leaf supporting the leading lateral shoot; peduncle (0–)0.5–1.8 cm; rays 0.3–1 cm, glabrous. Bracts 0. Umbellules (1–)2(–3); pedicels 0.9–1.8 mm, glabrous. Bractlets 2–4(–6), persistent, 1.5–3.5(–4.5) × 0.5–1.2(–1.5) mm, obtuse, with 3 veins; membranous border indistinct or absent. Flowers 3–7 per umbellule; sepals absent or indistinct; petals white, 0.6–1 × 0.45–0.65 mm; filaments 0.3–0.5 mm; anthers purplish, 0.2–0.3 mm. Fruit elliptic to oblong in outline; carpophore absent (the adaxial sides of the mericarps are connected via a thin longitudinal membrane, which leaves no trace when the fruit splits at maturity). Mericarps (2.3–)2.7–3.5 × 0.7–1.1 × 0.7–1.1 mm (length/width ratio 2.9–4.3); ridges 5, straw-coloured to light brown, in cross section high, rather broad and rounded; valleculae rather narrow, each with 1 dark brown vitta; stylopodium indistinct, flat, 0.4 mm wide; style 0.2–0.3 mm, directed outwards. – Early summer to mid-summer.
[2n=22]
Distribution. Nem. – Generally declining. D throughout the country; fairly common in NJy and VJy, elsewhere now rare. S scattered all over Sk and in coastal Hl, rare in central Bl, Öl (known from 7 localities), Klm (Söderåkra and Torsås, in running water), southwest SmI (Burseryd and Villstad, Berga and the water system of the lake Åsnen; formerly also Hinneryd and Traryd), southern BhG and southeastern Dls; Vg Bolum (Hornborgasjön) 1949-98, Mårdaklev (Ätran) 1928, Lidköping 1830’s, Östra Frölunda (Ängasjön).
W Europe, NW Africa.
Habitat. In and at shallow freshwater; as an aquatic down to c. 1 m depth, when terrestrial usually on damp, temporarily inundated soil (preferably sand mixed with, or covered by, organic sediments). Light-demanding and very dependent on open soil; in moderately eutrophic as well as oligotrophic habitats, and in lime-rich as well as base-poor areas. Coastal pools and ponds, alvar pools (in S Öl), lake shores, ditches, ponds in pastures, dams; rarely in small streams. A poor competitor, strongly favoured by trampling and grazing, and possibly by short-term water regulation (which creates areas where competition is low or absent), but sensitive to drainage and overgrowth.
Biology. Presumably autogamous; the stamens have short filaments keeping the anthers almost at the same level as the small stigmas, which are receptive at anther dehiscence.
Similar taxa. Helosciadium inundatum in the vegetative state, with only submerged, narrow-lobed leaves present, may resemble a Ranunculus of subgen. Batrachium, but H. inundatum has pinnatifid leaves, with slightly flattened and distinctly veined primary lobes. Batrachium leaves are always palmate and the primary lobes are ± terete, without a distinct vein.
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2. Helosciadium repens (Jacq.) W.D.J. Koch map
Koch, Gen. pl. Umbell.: 126 (1824). – Sium repens Jacq., Fl. austr. 3: 34, t. 260 (1775). – Apium repens (Jacq.) Lag. (1821). – Described from Austria.
D Krybende Sumpskærm. S sumpfloka.
Literature. Tutin 1980 (ill.).
Helophyte. Perennial, 2.5–9(–13) cm. Stem creeping and rooting at nodes, 0.8–1.6 mm thick, widely hollow, violet or pale, ribbed or sulcate. Leaves all cauline (sometimes up to four additional leaves develop from each axillary bud); sheath distinct, 0.4–1.3 cm, membrane-bordered, usually not purplish; petiole 3.4–9.5(–14) cm; blade 1-pinnate, 1.6–4.5(–9) × (0.9–)1.4–2.3 cm, with a length/width ratio of 1.4–2.5(–3.9). Leaflets sessile, 3–5 pairs; angle leaflet/rachis 65–85°. Apical leaflet 1–2-pinnatifid, with 1–2 pairs of primary lobes; petiolule 1.1–7.5 mm; blade 3.2–10 × 3.8–13 mm (length/width ratio 0.6–0.85); base cuneate to truncate, rarely cordate; margin not or indistinctly papillose, with cuspidate to acuminate teeth (tips sometimes purplish); apical lobe acute to obtuse, 0.8–2.5 × 1.2–2.3 mm (length/width ratio 0.7–1.7).
Umbels with a 1.5–7 cm long peduncle; rays 0.9–2 cm, glabrous. Bracts 3–5, persistent, 2.9–5.5 × 1–2 mm, obtuse, white-bordered, with 3–5 veins. Umbellules 4–6; pedicels 1.8–2.6 mm, glabrous. Bractlets 5–6, persistent, 2.2–3.1 × 0.8–1.2 mm, obtuse, not or indistinctly membrane-bordered, with 3 veins. Flowers 13–22 per umbellule; sepals indistinct; petals white, 0.6–0.8 × 0.5–0.7 mm; filaments 0.5–0.8 mm; anthers purplish, 0.25–0.3 mm. Fruit broadly ovate to orbicular in outline; carpophore entire or almost entire. Mericarps 0.9–1.1 × 0.5–0.8 × 0.6–0.8 mm (length/width ratio 1.3–2); ridges 11, low, narrow and rounded, sometimes slightly undulating,; stylopodium indistinct, flat, 0.3 mm wide; style 0.4–0.5 mm, directed outwards. – Mid-summer to autumn.
[2n=22]
Distribution and habitat. Indigenous. D only known from eastern FyL: Midskov since 1811 (pools and wet meadows, latest observation 1998), Hesselager 1926–56 (wet ground between shore ridges). – A record from S BhG Göteborg (Blom 1961) is due to confusion with H. nodiflorum.
W and C Europe.
Similar taxa. Helosciadium repens is similar to H. nodiflorum (rare casual).
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Rare casual
Helosciadium nodiflorum (L.) W.D.J. Koch 1824 ( Apium nodiflorum (L.) Lag. 1821). F koiranselleri. N nikkeselleri. S fränefloka. – Lit.: Tutin (1980; ill.). – Similar to H. repens (2), but stem rooting only at the lowest nodes; umbels without bracts; peduncles shorter than the rays. Fruit as in H. inundatum (1), but mericarps c. 2 mm long, with ridges slightly lower and broader in cross section. – [2n=22]
Docks, partly with ballast. D Sjæ Greve 2005 (weed in nursery). N Ak Oslo 1882, MR Kristiansund 1868. S BhG Göteborg (Frihamnen 1941–44), Ringön 1955. F V Turku 1884 (with ballast). – In and along freshwaters from Caucasus to Britain. Records from Central Asia are uncertain due to confusion with H. repens. - Map (not in the book).
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