Ranunculus confervoides (Fr.) Fr.
White water-buttercup.
Ranunculaceae, buttercup family.
Summa Veg. Scand. 139. 1845.
Nomenclatural section used by Flora of North America project Batrachium confervoides Fr., Bot. Not. 1845: 121. 1845.
Type: Finland: Oulu, leg. Ångström (UPS) lectotype, selected by Jonsell, Nord. J. Bot. 16: 7. 1996.
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.) C.D.K.Cook, Mitt. Bot. Staatssamml. München 6:
622. 1967.
Ranunculus. trichophyllus Chaix subsp. lutulentus
(E.P.Perrier & Songeon) Vierh., Abh. Zool.-Bot. Ges. Wien 16: 109. 1935.
Batrachium trichophyllum (Chaix) Bosch subsp. lutulentum
(E.P.Perrier & Songeon) Janch., Cat. Fl. Austr. 2: 196. 1958.
?Batrachium circinatum (Sibth.) Spach subsp. subrigidum (Drew)
Á. Löve & D. Löve, Bot. Not. 128: 512. 1976.
Ranunculus subrigidus W.B.Drew, Rhodora 38: 39. 1936.
?Ranunculus circinatus Sibth. var. subrigidus (W.B.Drew)
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(Sibthorp) Spach subsp. subrigidum (W.B.
Drew) A. Löve & D. Löve;
B. flaccidum (Persoon)
Ruprecht;
B. longirostris (Godron) F.W. Schultz;
B.
trichophyllum (Chaix) Bosch;
B. trichophyllum subsp.
lutulentum (Perrier & Songeon) Janchen ex V.V. Petrovsky;
Ranunculus aquatilis var.calvescens (W.B. Drew) L.D. Benson;
R. aquatilis var. capillaceus (Thuillier) DC;
R.
aquatilis var. eradicatus Laestadius;
R. aquatilis var.
harrisii L.D. Benson;
R. aquatilis var. longirostris
(Godron) G. Lawson;
R. aquatilis var. porteri L.D. Benson;
R. aquatilis var. subrigidus (W.B. Drew) Breitung;
R.
circinatus Sibthorp var. subrigidus (W.B. Drew) L.D. Benson;
R. confervoides (Fries) Fries;
R. longirostris Godron;
R. subrigidus W.B. Drew;
R. trichophyllus Chaix;
R.
trichophyllus var. calvescens W.B. Drew;
R. trichophyllus
var. eradicatus (Laestadius) W.B. Drew;
R. trichophyllus
subsp. lutulentus (Perrier & Songeon) Vierhapper.
Vegetative morphology. Plants perennial herbs; 5–40 cm high; totally submerged much branch aquatic with finaly divided flaccid leaves which collapse when withdrawn from water. Roots 0.3–0.4 mm in diameter, at lowest nodes on stem. Caudex absent. Aerial stems erect, or prostrate; stems have large air chambers in cortex; glabrous. Leaves distributed along the stems; alternate. Stipules present; scale-like; not sheathing; colorless. Petioles 4–11 mm long; glabrous. Blades 4–11 mm long; 7–23 mm wide. Blades spreading; herbaceous; filiform-dissected. Blades adaxial surface glabrous. Blades abaxial surface glabrous.
Reproductive morphology. Flowering stems present. Flowering stems conspicuously taller than the leaves; without leaves in the upper half; glabrous. Flowers solitary; medium-sized, 5–15 mm in diameter or length. Perianth present. Calyx sepals 5; free; 2–4 mm long. Calyx green; herbaceous; glabrous. Petals free; 5; white, or white and yellow; petals may be white with yellow claws; obovate; unlobed; 4–7 mm long. Stamens 10–20; filaments glabrous. Anthers yellow; ellipsoid. Nectaries present (nectar scale forms a shallow pocket or sometimes greatly reduced). Receptacle 1.5–2.5 mm high (densely pubescent). Carpels apocarpous; 15–25. Ovaries elliptic; ovary abruptly tapering to style; glabrous, or hairy. Styles 0.2–0.4 mm long. Stigmas per style 1. Ovules 1. Fruit sessile. Fruit dry; an achene; obovate; indehiscent. Fruit 1–1.8 mm long; 0.8–1.2 mm wide; yellowish, or black (achenes glabrate or with some hairs persisting on or near the dorsal sutures); surface venation reticulate (roughly transversely-ridged). Styles remaining straight; persisting in fruit 0.2–1.2 mm long. Seeds 1.
Chromosome information. 2n = 16, 32, 48. 2n= 16
(2x). - Sørensen and Westergaard in Löve and Löve (1948,
1956b Iceland?Greenland?).
24 (3x). - Zhukova et al. (1977a north
eastern Asia).
32 (4x). - Böcher and Larsen (1950);
Löve and Löve (1956b Iceland); Jørgensen et al. (1958
Greenland); Zhukova and Petrovsky (1971 Wrangel Island); Löve and Löve
(1982 arctic Canada).
48 (6x). - Zhukova (1982 north eastern Asia).
Distribution. Northern hemisphere distribution: circumboreal; Greenland, St. Pierre and Miquelon, Canada, United States, Eurasia. Low arctic. Range in the Canadian Arctic Archipelago limited. Uncommon. Arctic Islands: Baffin, Devon, Ellesmere, Victoria.
Ecology and habitat. Substrates: around the margins of ponds, along streams, seashores; aquatic, or imperfectly drained moist areas; acidic, or calcareous (saline, clayey or sandy seashores and salt marshes).
Notes. This species 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 (FNA). This variety has all of its
leaves filiform-dissected while var. aquatilis has laminate and
filiform-dissected leaves.
Elven et al. (2002) noted that a caseastern
Canada be made for describing this taxon within the genus Batrachium but
at ths time it is best kept as a Ranunculus. The identity of the arctic
American plants is disputed based on three main 'hypotheses'.
Most
Eurasians, also those familiar with the arctic American plants, identify them
with the arctic-alpine entity named as 'confervoides', described as
variety ('eradicatus') in 1839 by Laestadius and as species
('confervoides') in 1845 by Fries. The 'lutulentus' name is also
assumed to belong to the same entity. Some European authors consider it as a
race of R. trichophyllus or R. aquatilis but Nordic authors (in
the area where both 'aquatilis', 'confervoides' and
'trichophyllus' occur) concur in regarding it as a well differentiated
species. Its species epithet differs within the two genera: either Batrachium
eradicatum (Laest.) Fr. 1843 or Ranunculus confervoides Fr. 1845.
Many North American authors have named it as Ranunculus circinatus
var./subsp. subrigidus, i.e., relating it to the mainly Eurasian species
R. circinatus. However there is little morphological similarity between
the arctic American plants and the European R. circinatus, and there also
is a ploidy difference. Ranunculus circinatus is diploid (2n=16) both in
northern Europe and further south in North America whereas the northern entity
is mainly or exclusively tetraploid (2n=32) both here and there.
Flora of
North America, Vol. 3 places almost all North American plants into Ranunculus
aquatilis var. diffusus. This entity is described from Britain
(Withering 1796) and is currently recognised also in northern Europe but as
distinctly different from the northern plants (see Dahlgren and Jonsell in
Jonsell 2001, Flora Nordica 2). The synonymy in Flora North Amererica shows that
there the taxon is considered in a vastly wider sense than in northern Europe.
Illustrations. • Plant habitat. White flowered butter-cup with flowers borne above the surface of the water and finely divided leaves below the water surface. Manitoba, Churchill. Aiken and Brysting 01–035. CAN. • Close-up of plant. Terrestrial form with small leaves on short petioles and short-pedicelled, very small flowers. Norway: Finnmark, Porsanger, Trollholmsund. 6/7–1984. Photo: R.Elven. • Long aquatic leaves. Herbarium specimen with divided aquatic leaves about 2 cm long, and fl ower buds. N.W.T., Kazan River, below Yathkyed Lake, 16–26 August, 1930, A.E. Porsild. CAN 55386. • Close-up of flower. Herbarium specimen with divided leaves about 0.5 cm long and flower pressed so that the smaller, darker sepals are seen against the petals.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
