Flora of the Canadian Arctic Archipelago

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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 subrigidus W.B. Drew

Ranunculaceae, Buttercup family.

Published in Rhodora 38: 39. 1936.

Type: Quebec, York River, 29 July 1905, Williams, Collins and Fernald. Holotype GH.

Synonymy. Ranunculus aquatilis L. var. subrigidus (W.B. Drew) Breitung

Ranunculus circinatus Sibth. var. subrigidus (W.B. Drew) L. Benson

Vegetative morphology. Plants 5–15(–40) cm high; perennial herbs; not caespitose. Only fibrous roots present. Delciate pale brown aquatic roots 0.3–0.4 mm wide developed along the stem. Ground level or underground stems absent. Leaves present; not heterophyllous; distributed along the stems; alternate; dying annually and non-persistent. Stipules present (as stipular sheaths about 75–100% adnate to the petioles); 3.8–5 mm long; 1.2–2 mm wide; sheathing (adnate to the petiole for about 75% of the length); brown (pale), or colourless; hairy; pilose (tending towards stiffish hairs); apex acute, or rounded. Petioles 1.5–5 mm long (surrounded by the adnate stipule). Sheaths present (as stipular sheaths that are mostly broad and well developed on the majority of the leaves). Leaves not grass-like. Blades 2.5–10 mm long, triangular, flat (or usually with tangled leaf divisions), veins palmate. Blade adaxial surface glabrous (when young) or hairy, hairs villous or strigose, hairs simple, hairs sparse, hairs white, or translucent. Blade abaxial surface hairy, hairs strigose, hairs sparse, hairs white, hairs straight, hairs appressed. Blades cut into linear divisions (initially 3 divisions that are further subdivided; the blades remaining "subrigid" or rather flaccid, on withdrawal from water). Blade margins entire; apices obtuse, or rounded (with a tuft of 2-several stiff trichomes on the top).

Reproductive morphology. Flowering stems without leaves. Flowering stems glabrous. Flowers solitary. Flowers conspicuously larger than the flowers of the European R. circinatus. Sepals conventional; 5; free; 2.5–3 mm long; 1–2 mm wide; green, or brown; herbaceous, or scarious (slightly). Calyx glabrous. Petals conventional; free; 5; white; obovate; unlobed; 5–6 mm long; 2–2.5 mm wide. Stamens 10–22; stamen filaments glabrous. Anthers yellow; 0.6–0.8 mm long. Nectaries present. Receptacle 1.75–2 mm high (c.f. about 1.25 mm in R. longirostris). Ovary carpels 30–80 (average 40 or less in Arctic Island specimens); apocarpous. Styles 0.2–0.5 mm long (persisting in the fruit as a short beak). Stigmas per ovary 1. Placentation parietal. Ovules per ovary 1. Fruit sessile; dry; an aggregate of achenes; ovoid (below the beak); brown, or golden brown; 1–1.5 mm long (average length 1.25 mm, c.f. R. longirostris average length 1.5 mm; surface rather finely rugose); 0.5–1 mm wide; hairy (conspicous stiff trichomes 0.5–0.6 mm long); surface appearing veinless; indehiscent. Styles remaining straight (or somewhat curved). Seeds 30–80 (usually about 40 in achenes).

Ecology and habitat. Substrates: around the margins of ponds, marshes; aquatic; silt; calcareous (waters).

North American distribution. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories, Nunavut Islands, continental Nunavut. Range in the Canadian Arctic Archipelago widespread. Uncommon (or relatively rarely collected). Arctic. Arctic islands: Baffin, Ellesmere, Victoria, Southampton, Coats (Prince Charles).

General notes. In the protologue (1936), Drew noted that the typical form of this species is superficially similar to the European R. circinatus with which it has long been confused. However, the petals are larger than those of the European plant, and consequently, there are a greater number of veins that are usually more forked towards the distal end of the petal. The leaves of subrigidus are only ‘subrigid’ and rather flaccid, whereas those of European R. circinatus are usually very rigid and stiff. Immature carpels of R. subrigidus have long styles, which do not usually persist to any marked extent at maturity. Drew provided illustrations of the leaves, receptacle hairs, and achenes.

Illustrations. • Habitat. White flowered buttercups that are yellow in bud, with flowers borne above the surface of the water and finely divided leaves below the water surface. Approaching 5 to 15 cm in height. Manitoba, Churchill. Aiken and Brysting 01–035. CAN. • Close-up of plant. Aquatic plant with stiffish "subrigid" leaves and flowers conspicuously larger than those of the European R. circinatus with which our R. subrigidus may be confused. Nunavut, Victoria Island. CAN 273630. • Vegetative plant. Vegetative plant with leaves approaching 1 cm long and subrigid. Nunavut, Southampton Island. CAN 255722. • Stem with stipules. Alternate leaves with stipular sheaths that are broad, well-developed and adnate to the petioles about 75 % (lower sheath) and 100% upper sheath. Nunavut, Victoria Island, Cambridge Bay. CAN 273630. • Close-up of stipule and leaf. Note the surface of the stipule, the surfaces of the leaves in bud, and the lower portions of the leaf divisions are covered with stiff hairs. Nunavut, Victoria Island, Cambridge Bay. CAN 273631. • Stem apex with flower buds. Stem apex showing flower bud on conspicuous peduncle, young flower bud surrounded by stipular sheath, and leaf with a stipular sheath. N.W.T., Nahanni National Park. CAN 482970. • Petals with forked veins. Petals 5–6 mm long and 2–2.5 mm wide. Flowers are larger than those of the European species (R. circinatus) with which it may be confused, and consequently also with a greater number of veins that are usually more forked towards the distal end of the petal. Note calyx glabrous and about one half the length of the petals. Nunavut, Victoria Island, Cambridge Bay. CAN 273620. • Type specimen. Label data: Type specimen of Ranunculus codyanus Boivin. Nunavut, Southampton Island, W.J. Cody 1712, 1 Aug. 1948. Petals white, yellow at the base. In muck around drying up pool and in water (3") rooted in muck. Near South Bay Beach. Very common in one pool only. DAO 545932. • Close-up of single plant. Plant on the upper left-hand corner of the type specimen of Ranunculus codyanus Boivin. DAO 545932. • Flower on type specimen. Close-up of the only flower on the type specimen of Ranunculus codyanus Boivin. Note relatively long petals with forking veins, and hairs developing on the receptacle. DAO 545932. • Close-up of fruit. Left, receptacle of fruiting stage covered with long trichomes. Right, two achenes with the characteristic ridges of taxa in subgenus Batrichium. Type of Ranunculus codyanus Boivin. DAO 545932. • 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.

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