Flora of the Canadian Arctic Archipelago


S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, L.J. Gillespie, A.K. Brysting, H. Solstad, and J.G. Harris

Ranunculus aquatilis L. var. diffusus With.

English: White water-crowsfoot,

French: Renoncule de Lapponie.

Ranunculaceae, Buttercup family.

Published in Arr. Brit. Pl. ed. 3, 2: 507. 1796.

Type: Protologue, no type information cited

Synonymy. Ranunculus trichophyllus var. capillaceus (Thuillier) DC., Prodr. 1: 26. 1824.

Ranunculus aquatilis var. capillaceus (Thuillier) L. D. Benson, Amer. Midl. Natural. 40: 237. 1948.

Ranunculus aquatilis L. var. eradicatus Laest., Nova Acta Soc. Scient. Ups. 11: 242. 1839.

Batrachium eradicatum (Laest.) Fr., Bot. Not. 1843: 114. 1843.

Ranunculus trichophyllus Chaix subsp. eradicatus (Laest.) Frew, Thodora, 38:33. 1936.

Ranunculus trichophyllus Chaix var. eradicatus (Laest.) W.B. Drew

Ranunculus trichophyllus Chaix subsp. eradicatus (Laest.) C.D.K. Cook, Mitt. Bot. Staatssamml. München 6: 622. 1967.

Ranunculus. trichophyllus Chaix subsp. lutulentus (E.P. Perrier and Songeon) Vierh., Abh. Zool.-Bot. Ges. Wien 16: 109. 1935.

Batrachium trichophyllum (Chaix) Bosch subsp. lutulentum (E.P. Perrier and Songeon) Janch., Cat. Fl. Austr. 2: 196. 1958.

?Ranunculus subrigidus W.B. Drew, Rhodora 38: 39. 1936.

?Ranunculus circinatus Sibth. var. subrigidus (W.B. Drew) L.D. Benson, Amer. Midl. Natural. 40: 240. 1948.

?Batrachium subrigidum (W.B. Drew) Ritchie, Can. J. Bot. 34: 300. 1956.

?Ranunculus aquatilis L. var. subrigidus (W.B. Drew) Breitung, Amer. Midl. Natural. 58: 32. 1957.

Batrachium circinatum (Sibth.) Spach subsp. subrigidum (W.B. Drew) Á. Löve and D. Löve, Bot. Not. 128: 512. 1976.

Ranunculus longirostris Godron, Mem. Soc. Roy. Nancy 39: 1839(1840).

Batrachium longirostre F.W. Schultz, Arch Fl. Fr. i 71. 1844.

Batrachium trichophyllum (Chaix) Bosch, Prod. Fl. Bot. 7; Des Moul. in Act. Soc. Linn. Bord. xx. 456. 1859.

Ranunculus confervoides (Fr.) Fr., Summa Veg. Scand. 139. 1845.

Batrachium confervoides Fr. Bot. Not. 1845: 121. 1845.

Ranunculus trichophyllus var. confervoides (Fr.) Rikli. 1900.

Ranunculus trichophyllus var. calvescens W.B. Drew, Rhodora 38: 32. 1936.

Ranunculus aquatilis var. calvescens (W.B. Drew) L. D. Benson, Amer. Midl. Natural. 40: 239. 1948.

Ranunculus aquatilis var. harrisii L.D. Benson, Amer. Midl. Natural. 40: 236. 1948.

Ranunculus aquatilis var. porteri L.D. Benson, Amer. Midl. Natural. 40: 236. 1948.

Vegetative morphology. Plants 5–40 cm high (0.3–1(-1.5) mm thick); annual herbs; not caespitose (pale green to whitish green, translucent). Only fibrous roots present. Roots 0.3–0.4 mm in diameter, at lowest nodes on stems. Ground level or underground stems horizontal; stoloniferous (floating stems in the water); elongate; 0.8–1.2 mm wide. Caudex absent. Aerial stems erect (growing up through the water), or prostrate (at the water surface). Leaves present; not heterophyllous (a contrast with subsp. aquatilis: broad-lobed leaves absent; terrestrial plants 5–7(-12) cm high; branches from the base, decumbent, ultimate leaf segments flattened, short); distributed along the stems; alternate; dying annually and non-persistent. Stipules present (ovate); glabrous, or hairy (slightly). Petioles present; 4–11 mm long; glabrous. Leaves not grass-like. Blades 4–11 mm long, 7–23 mm wide (shorter or as long as the corresponding internode), spreading, reniform (to suborbicular, usually 4 times divided, segments in more than one plane; fan-shaped, capillary, ultimate ones narrowing outwards, less than 0.1 mm wide, long in relation to the whole leaf, 4–10 mm), flat, veins palmate. Blade adaxial surface glabrous. Blade abaxial surface glabrous. Hydathodes present but inconspicuous.

Reproductive morphology. Flowering stems two or more per plant. Flowering stems stems have large air chambers in cortex. Flowers solitary (borne in the axils of leaves, 'leaf-opposed', pedicels 1–2 (-5) cm, thin). Flowers medium-sized. Sepals conventional; 5; free; 2–5 mm long; 2–4 mm wide; green (sometimes blue-tipped); herbaceous. Calyx glabrous. Petals conventional; free; 5; white, or white and yellow; petals white with yellow claws; obovate, or spatulate (not contiguous); unlobed; 3.5–7 mm long; 2–3(–5) mm wide (caducous). Stamens 4–8(–10); stamen filaments glabrous. Anthers yellow; ellipsoid; 0.5–0.7 mm long. Nectaries present (nectary scale forms a shallow pocket or sometimes greatly reduced; luneate). Receptacle 1.5–2.5 mm high; surface hairy (densely pubescent). Ovary carpels 15–25; apocarpous. Ovaries elliptic; abruptly tapering to style; glabrous, or hairy. Styles 0.2–0.4 mm long. Stigmas per ovary 1. Placentation parietal. Ovules per ovary 1. Fruit sessile; dry; an aggregate of achenes; obovate; yellowish, or black (achenes glabrescent or with some hairs persisting on or near the dorsal sutures); 1–1.8 mm long; 0.8–1.2 mm wide; surface venation reticulate (roughly transversely ridged); indehiscent. Achenes elliptic in outline, slightly compressed 1–1.5 × 0.7–1.2 mm. Styles remaining straight; persisting in fruit 0.2–1.2 mm long. Seeds 1; surfaces reticulate (finely on the achenes or with low transverse ridges; beak 0.1–0.3 mm).

Chromosome information. 2n = 16, or 32, or 48.

2n (2x) = 16. Sørensen and Westergaard, in Löve and Löve (1948, 1956, Iceland? Greenland?);

2n (3x )= 24. Zhukova et al. (1977, northeastern Asia);

2n (4x) = 32. Böcher and Larsen (1950); Löve and Löve (1956, Iceland); Jørgensen et al. (1958, Greenland); Zhukova and Petrovsky (1971, Wrangel Island); Löve and Löve (1982, Arctic Canada);

2n (6x) = 48. Zhukova (1982, northeastern Asia).

Ploidy levels recorded 2x/3x/4x/6x.

Ecology and habitat. Substrates: around the margins of ponds, along streams, seashores; aquatic, imperfectly drained moist areas; acidic, or calcareous (saline, clayey or sandy seashores and salt marshes). Porsild (1957) reported this species from shallow ponds or sometimes in running water, less commonly in brackish lagoons.

North American distribution. Alaska, Yukon, Northwest Territories Islands (?), continental Northwest Territories, Nunavut Islands, continental Nunavut, northern Quebec, Labrador. Range in the Canadian Arctic Archipelago limited. Uncommon. Low Arctic. Arctic islands: Baffin, Devon, Ellesmere, Victoria.

Northern hemisphere distribution. Circumpolar, or circumboreal. Northern Iceland, Northern Fennoscandian, Kanin–Pechora, Polar Ural – Novaya Zemlya, Yamal–Gydan, Taimyr – Severnaya Zemlya, Anabar–Olenyok (?), Kharaulakh, Yana–Kolyma (?), West Chukotka, South Chukotka (?), West Alaska, North Alaska – Yukon, Central Canada, Labrador – Hudson Bay, Ellesmere Land – Peary Land, West Greenland, East Greenland.

General notes. Ranunculus aquatilis var. diffusus belongs to the subgenus Batrachium (DC) A. Gray (Flora of North America, Whittemore 1997). There has also been evidence presented to raise it to genus Batrachium Gray (Elven et al. 2005). Although recognition of Batrachium as a genus separate from Ranunculus is not in accordance with the work of Johansson (1998), [Pl. Syst. Evol. 213: 253–261] based on cpDNA restriction analysis, Elven et al. (2003) proposed keeping the name Batrachium in a northern context because it is a fairly distinct segregate. We follow the former treatment here.

Ranunculus aquatilis shows many variants based on achene beak length and pubescence of the receptacle, which intergrade with each other so only two varieties are recognised in North America (Whittemore 1997). This variety has all of its leaves filiform-dissected while var. aquatilis has laminate and filiform-dissected leaves.

Whittemore divided R. aquatilis into two subspecies, and his R. aquatilis var. diffusus was quite inclusive. He commented "Ranunculus aquatilis var. diffusus shows geographical variation, and some regional forms have been recognised as varieties. Dwarf creeping arctic plants m ay be called R. aquatilis var. eradicatum, plants with linear non-capillary leaf segments from the northern Great Basin may be called R. aquatilis var. porteri, and very robust plants from Oregon and northern most California may be called R. aquatilis var. harrisii. Extreme forms of these races are recognizable, but they intergrade and many specimens cannot be confidently assigned to one or another of them" (Whittemore 1997, p 132).

Elven et al. (2005) split off some of the entities included here into Batrachium eradicatum, which encompass the synonym epithets "eradicatus," lutulentus" "subrigidus," and "confervoides."

Ranunculus aquatilis var. diffusus is self-compatible, largely cleistogamous, with flowers pollinated in the submerged state; the fruit setting is very rich.

Brayshaw (1989) noted that the variation in leaf form in this and related species, is of a kind that has given rise to endless confusion regarding the identities and limits of species and varieties; a large number of species had varieties have been described based on the diversity of form, accounting for some of the difficulties in coming to an agreement about the taxonomic treatment of this group.

Illustrations. • Habitat: Baffin. Plants stranded on damp mud where a shallow pool has dried up. Nunavut, Baffin Island, Iqaluit, Sylvia Grinell Park. 19 August, 2006. Aiken 06–035. CAN. • Close-up of flower and fruit. Flower with white petals that have a yellow splash of colour at the base Nunavut, Baffin Island, Iqaluit, Sylvia Grinell Park. 19 August, 2006. Aiken 06–035. CAN. • Close-up of plant. Terrestrial form with small leaves on short petioles and small flowers on short pedicels. Norway, Finnmark, Porsanger, Trollholmsund. 6 July, 1984. Phototograph by R. Elven. • Leaves and stipules. Note ovate glabrous, membranous stipules at the base of finely divided leaves. Nunavut, Baffin Island, Mallik Island. CAN 342871. • Surface view of flower. Note spatulate petals with greatest width about 2/3 from the base and the limited number of stamens. N.W.T. CAN 216235. • Close-up of receptacle. Receptacle with achenes removed. Note long hairs. Nunavut, Cape Dorset. CAN 55333. • Arctic Island Distribution.

This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.

Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.

Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa.