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

Haloragaceae R. Br.

English: Water milfoil family.

Haloragaceae, Water-milfoil family.

Vegetative morphology. Plants 5–20 cm high (in Arctic collections, commonly to 100 cm in southern Canada); perennial herbs; sometimes vegetatively proliferating by bulbils on stems or leaves ((specialised overwintering turions), or sometimes vegetatively proliferating by fragmentation. Only fibrous roots present. Roots Roots free-floating fragments developing white roots. Aerial stems erect. Leaves heterophyllous (often with smaller, thicker, dark green turion leaves at the base of the plant and larger, paler, thinner, green summer leaves); distributed along the stems; whorled; dying annually and non-persistent (summer leaves), or persistent (turion leaves persist for more than 12 months in Arctic specimens). Petioles 0.1–0.2 mm long. Leaf blades simple (cut into linear divisions). Leaf blade bases cuneate. Blades 10–25 mm long (in Arctic specimens, to 45 mm long in plants growing in southern Canada), 15–35 mm wide (Arctic specimens), spreading, ovate (broadly, in outline), flat. Blade adaxial surface glabrous. Blade abaxial surface glabrous. Blades cut into linear divisions (fewer than 14 on either side of the midvein). Blade margins deeply divided, glabrous. Hydathodes absent (on the leaves, present as dark pores on the stems).

Reproductive morphology. Flowering stems circular or oval in cross section. Flowering stems with leaves; rooting at the lower nodes (especially in soft mud). Inflorescences without bulbils (in the Arctic, plants sometimes form bulb-like turions without flowering); spicate; terminal; 3–10 cm long; 0.4–0.6 mm wide; elongating as the fruit matures. Inflorescences main axis glabrous. Pedicels absent. Inflorescence 1 spikes (per stem). Bisexual spike(s) with empty bracts at the base (and bracteoles). Flowers small; radially symmetrical (actinomorphic); unisexual. Sepals conventional (male flowers), or absent (female flowers); 4; free; 0.5–1.5 mm long; 0.5–1.5 mm wide; green, or pink; herbaceous (if applicable). Calyx glabrous. Petals conventional (male flowers), or absent (female flowers); free; 4; pink (if applicable); ovate; unlobed; 0.2–0.4 mm long; 0.1–0.2 mm wide (male flowers). Stamens 8. Anthers yellow; 1–1.2 mm long. Ovary inferior; carpels 4; syncarpous. Styles absent (pinkish fluffy, sessile stigmas on the top of each carpel). Ovules per ovary 1. Fruit sessile; dry; a schizocarp (splitting into 4 mericarps), or a mericarp; ovoid, or oblong; brown; 1–2 mm long; 0.8–1.1 mm wide; glabrous; not distinctly flattened; schizocarpous. Seeds 1.


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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