Myriophyllum sibiricum Komorov
Water milfoil.
Haloragaceae, watermilfoil family.
Feddes Repert. 13: 168. 1914
Type: Russian Far East: Kamchatka River basin, leg. V.L.Komarov (LE) lectotype, selected by Aiken qne Cronquist Taxon 37: 959. 1988.
Myriophyllum exalbescens Fernald, Rhodora 21: 120. 1919.
Myriophyllum. spicatum L. subsp. exalbescens (Fernald)
E.Murray, Kalmia 12: 22. 1982.
M. spicatum auct., non L. 1753
Myriophyllum exalbescens Fernald
Myriophyllum spicatum
subsp. exalbescens (Fernald) Hultén
Myriophyllum
spicatum var. exalbescens (Fernald) Jepson
Myriophyllum
spicatum var. squamosum (Laestad. ex Hartman) Hartman
Vegetative morphology. Plants perennial herbs (from persisting over-wintering buds or "turions"); 5–20 cm high (in Arctic collections, commonly to 100 cm in southern Canada); aquatic, with submerged, erect stems that may branch at intervals along the stem; rarely flowering in the eastern Canadian Arctic islands; vegetatively proliferating by bulbils or fragmentation (specialized overwintering turions). Ground-level or under-ground stems not developed horizontally or vertically (plants grown from turions have a U-shaped base to the stem). Aerial stems erect; glabrous. Leaves heterophyllous (often with smaller thicker dark green turion leaves at the base of the plant and larger, green summer leaves); distributed along the stems; whorled; simple (pinnately divided); existing for a single season or less (summer leaves), or evergreen (turion leaves persist for more than 12 months in Arctic specimens). Petioles 0.1–0.2 mm long. Blades 10–25 mm long (in Arctic specimens to 4.5 cm long in plants growing in southern Canada); 15–35 mm wide (Arctic). Blades adaxial surface glabrous. Blades abaxial surface glabrous. Blade margins cut into linear divisions. Conspicuous hydathodes present (as dark pores on the stems).
Reproductive morphology. Flowering stems present. Inflorescence spicate. Flowers small, less than 5 mm in diameter or length. Calyx absent (female flowers), or present (male flowers). Petals absent (female flowers), or present (male flowers, caducous); free; 4; pink. Flowers unisexual (female flowers basal usually, male flowers towards the top of the inflorescence, occasionally bisexual flowers occur in the middle of the spike). Stamens 8. Gynoecia superior. Carpels syncarpous. Styles absent. Placentation axile. Ovules 1 (per locule). Fruit dry; a schizocarp (splitting into 4 mericarps); schizocarpous. Fruit 1–2 mm long; 0.8–1.1 mm wide; brown; glabrous (with slight warts). Styles modified and persisting. Seeds 1 (per mericarp); 1–1.9 mm long; white; with surfaces smooth.
Chromosome information. 2n = 42. Löve (1961 North America?, 1983 Iceland); Packer (1964 western Canada); Löve and Ritchie (1966 northern Canada); Aiken (1978); Löve and Löve (1982a central Canada). Supposed basic chromosome number of family 6x.
Distribution. Northern hemisphere distribution: circumboreal; Greenland, Canada, United States, Eurasia, Norden. Low arctic, or boreal. Range in the Canadian Arctic Archipelago limited. Rare. Arctic Islands: Baffin, Victoria, Southampton.
Ecology and habitat. Substrates: tundra ponds; aquatic; calcareous. Habitats: shallow, calcareous streams.
Notes. Porsild (1964) used the species name Myriophyllum
exalbescens Fernald and reported a single collection from the west coast of
Baffin Island as the only collection from the Arctic Archipelago. We are aware
of four other collections since then.
Aiken and Cronquist (1988) explained
why the name M. exalbescens falls into synonymy under M. sibiricum
which they lectotypified.
Plants collected from the Arctic Archipelago
reflect the short and cold growing season available for submerged aquatic
plants. The plants are usually 10–15 cm tall with evidence of the previous
season's turions in a characteristically curved base and smaller, thicker, dark
green leaves. Plants collected on Baffin Island, before the end of August were
already developing the next season's over-wintering turions without having
flowered. Plants on Southampton Island, that were flowering (see image library),
were growing in a very shallow pond, and had experienced a period of weather
with temperatures in the high 20's (°C) for several days.
The
"constipated duck" theory has been employed jokingly by the Aquatic Plant
Management Society as a possible explanation of the spread and distribution of
Myriophyllum spicatum in North America. Given the large flocks of
migrating birds that nest in the Arctic this may explain the occurrence of
Myriophyllum records on the Arctic Archipelago as plants that are
vegetative only and achieve such little annual growth, would be expected to
become weaker and die out over a relatively short period of time. While
definitive identification is difficult on vegetative specimens, the variation in
the shape of over-wintering turions and the transition between turion leaves and
summer leaves in different samples, lead S.G. Aiken to suggest that M.
verticillatum may also be present in the Arctic Archipelago (for turion
information see Aiken et al. (1979); Aiken and Waltz (1979).
Illustrations. • Herbarium sheet. Vegetative plants: note the characteristic U-shape at the base of plants that have grown from turions, longer summer leaves with thinner pinnately divided leaves that have more leaf divisions, and turions forming at the apex. CAN. • Plants in shallow pool. Mark Mallore, Canadian Wild Life Service, reaches into a bed of Myriophyllum sibiricum to try and insert a size marker. The marker tag is about 10 cm high, indicating that the water was very shallow. Nunavut, Southampton Island, Coral Harbour. Aiken and Brysting, 01–067. CAN. • Close up of plants. Young flowering stem above water, and many developing flowering stems underwater on the right hand side of the image. The plants are covered with silt and dust. The lowest whorl on the flowering stem has blooming female flowers. The right hand flower has four fluffy, pale yellow, sessile stigmas. The upper reddish whorls are female flowers in bud. Male flowers develop at the top of the inflorescence. Nunavut, Southampton Island, Coral Harbour. Aiken and Brysting, 01–067. CAN. • Arctic Island distribution.
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).
