Flora of the Canadian Arctic Archipelago
Tofieldiaceae, Tofieldia family.
Published in Bot. Zhurn. (Moscow and Leningrad) 79(12): 65. Jan.-Jul. 1995.
Vegetative morphology. Plants 5–20 cm high; perennial herbs; caespitose. Only fibrous roots present. Roots pallid-brown. Ground level or underground stems horizontal (rhizomes sometimes present, rarely collected: present on CAN 541779), or absent. Ground level or underground stems scales absent. Aerial stems erect. Leaves mainly basal; alternate; dying annually and non-persistent. Petioles absent. Sheaths absent. Ligules absent. Leaves grass-like. Blades 10–50(–70) mm long, 1–3 mm wide, spreading, straight, linear, veins parallel. Blade adaxial surface glabrous. Blade abaxial surface glabrous. Blade margins entire (sometimes minutely scaberulous on margins), glabrous; apices acuminate, or acute (but without calloses).
Reproductive morphology. Flowering stems circular or oval in cross section. Flowering stems with leaves, or without leaves. Inflorescences head-like; dense; oblong, or globose or sub-globose, or cylindrical; 0.5–1.5 cm long; 5–8 mm wide. Involucral bracts on pedicels with bract leaves (a specialised structure the "calyculus"). Flowers per inflorescence 4–15; small. Sepals conventional (white petaloid tepals); 3; free; 2–3 mm wide; green, or yellow, or purple; petaloid. Calyx glabrous. Petals conventional; free; same length as the calyx; 3; green, or white, or yellow, or purple; obovate; unlobed; 2–3 mm long. Stamens 6. Anthers yellow (and persisting); sub-globose; 0.3–0.4 mm long. Ovary superior; carpels 3; partly fused (incompletely fused at the apex). Ovaries glabrous. Styles absent (or very short with a stubby stigma on each carpel). Ovules per ovary 15–30. Fruit with calyx persisting; dry; a capsule; spherical, or ovoid, or obovate; black, or brown, or yellowish; 1–2 mm long; 1–2 mm wide; dehiscent. Seeds 6–30; 0.5–1 mm long; brown; surfaces smooth.
Ecology and habitat. Substrates: hummocks, snow patches, around the margins of ponds, river terraces, tundra; imperfectly drained moist areas, dry, moderately well-drained areas; gravel, silt, till, moss; with low organic content; acidic, or calcareous.
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. Arctic, Low Arctic. Arctic islands: Baffin, Devon, Banks, Victoria, Southampton.
General notes. This family is named for Thomas Tofield, 1730–1779, English Botanist.
Tamura (1998) placed the genus Tofieldia in the family Nartheciaceae, providing an extensive description of the family and indicating that it comprises 10 genera and about 72 species that are distributed mostly in the northern hemisphere and extending to northern South America. Since then the family Tofieldiaceae has been recognised as comprising 3–5 genera and about 27 species (angiosperm phylogeny website: www.mobot.org/MOBOT/Research/APweb/welcome.html); the remaining 4–5 genera are still within the family Nartheciaceae.
Tofieldiaceae are placed within the order Alismatales, but with only moderate support (Källersjö et al. 1998, Chase et al. 2000). This family has also been placed in the Dioscoreales, also with only moderate support (Chase et al. 2000, Caddick et al. 2002). Revel and Pires (2002) [Introduction to Volume 26, Flora of North America] indicated that Tofieldiaceae is removed from Takhtjan's circumscription of the Melantiales, and this dissociation is well supported by molecular and anatomical data (Zomlefer 1997a, b, Zomlefer et al. 2001).
Remizova and Sokoloff (2003) found additional features shared by Tofieldia and some of Alismatales s.str., Araceae and Acoraceae. In Tofieldia, as well as in species of Araceae with trimerous flowers, the outer median tepal occupies adaxial position (in the majority of monocots its position is abaxial). Tofieldiaceae is characterised by presence of a structure, usually described as calyculus, at the pedicel. The calyculus typically consists of three free or connate scales. The calyculus of Tofieldiaceae resembles the "spathe" of Hydrocharitaceae and (pseudo)whorls of bracts in Alismataceae. However, the calyculus also exhibits important features of a perianth whorl. The situation may be compared to some Alismatales where an exact "boundary" between structures of "flower" and "inflorescence" is often scarcely recognisable. A tendency to produce organs combining features of subtending bract and the first median abaxial phyllome on the pedicel is shared by Tofieldia pusilla, Acorus, Juncaginaceae, and some Potamogetonaceae. The data were found to support inclusion of Tofieldiaceae into the expanded order Alismatales.
In vegetative morphology, members of the tribe Tofieldieae have distichous, equitant, unifacial foliage leaves. The cotyledon has an assimilating elongated hyperphyll (Tamara 1998). The Tofieldieae have unique crystalline inclusions, druses in parenchymatous tissues, and prismatic crystals in the bundle sheaths (Ambrose 1980).
In reproductive morphology the ancestral form of inflorescence in this family may be a raceme which is found in some species of Tofieldia. Two arctic species of Tofieldia have a spike which is considered a derived form of inflorescence. Floral bracts are always present. Bracteoles are always present. The tepals and stamens are often almost free but basally connate in genera other than Tofieldia. The fusion of carpels in this family is often incomplete, the stigmatic tips of the carpels do not meet and no style is formed. The pollen grains are spheroidal, 14–36 microns in the longest axis. The exine is usually reticulate. Tofieldia palustris is homogamous, that is, the stigmas are receptive at the same time as the pollen is shed.
The carpellary sutures are open at anthesis and septal wing tips are loculicidally inrolled in Tofieldia. The ovules have a filiform chalazal hook, which seems to be an extension of the funiculus (Sterling 1978, 1979; Utech 1978). The floral anatomy and embryology are described by Tamura (1998). The fruits of this family are always capsules that dehisce septicidally in the Tofieldioideae. The seeds are always packed obliquely in the capsules in contrast to the horizontal packing of the compressed seeds in Liliaceae and related families. The seeds are often appendaged. Those of Tofieldida lack phytomelan but contain phlobaphene deposits.
The basic chromosome numbers of Tofieldioideae-Tofieldieae are x = 14–16. The basic numbers of x = 14, T. pusilla (Cave 1964), and x = 16, T. coccinea (Zhukova 1967a), seem to be derived. Chromosome size in this family is mostly very small, ranging from 0.7 to 1.7 microns in length at mitotic metaphase, which can be considered a primitive characteristic in monocots (Tamura 1995). The chromosomes at metaphase are all metacentric or submetacentric.
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..