Onagraceae A.L. de Jussieu
Fireweed family.
Onagraceae, fireweed family.
Vegetative morphology. Plants perennial herbs; (2–)5–30(–40) cm high (to 100 cm tall on continental North America); caespitose, or not caespitose. Caudex present, or absent. Ground-level or under-ground stems horizontal, or not developed horizontally or vertically (if applicable). Aerial stems erect, or ascending; glabrous, or sparsely hairy, or densely hairy (hairs inconspicuous, when present); stem hairs appressed, or spreading, or reflexed. Leaves distributed along the stems; alternate, or opposite (or pseudo-opposite); simple; existing for a single season or less. Petioles present, or absent; 0.5–2 mm long (if applicable); glabrous. Leaf blade bases obtuse, or acute, or attenuate. Blades (4–)10–60(–90) mm long; 1–15(–22) mm wide. Blades spreading; linear to oblanceolate; flat; veins pinnate, or appearing single-veined. Blades adaxial surface glabrous, or glabrescent. Blades adaxial surface hairs simple, unbranched. Blades abaxial surface glabrous, or glabrescent, or hairy. Blades abaxial surface hairs sparse, or moderately dense, or very dense. Blades abaxial surface puberulent (if applicable). Blades abaxial surface hairs white, or translucent hairs; curved (if applicable). Blade margins entire, or dentate (or shallowly sinuate, repand dentate). Leaf apices acuminate, or acute, or obtuse, or rounded.
Reproductive morphology. Flowering stems present. Flowering stems with leaves; glabrous, or hairy. Flowering stem hairs puberulent, or pubescent; simple; shorter than the diameter of the flowering stem; white or translucent. Flowers solitary, or in inflorescences. Inflorescence racemose (if applicable); terminal, or axillary; diffuse. Pedicels present; with non-glandular hairs (usually), or glabrous. Flowers per inflorescence 1–8(–20) (or 40 further south); small, less than 5 mm in diameter or length, or medium-sized, 5–15 mm in diameter or length, or large, more than 15 mm in diameter or length; actinomorphic. Calyx sepals 4; free; 3–18 mm long; 0.7–5.5 mm wide. Calyx green and red, or purple; without sessile glands; hairy; puberulent, or pubescent. Calyx hairs non-glandular; white or translucent. Petals free; 4; white, or pink, or purple; obovate, or spatulate; unlobed, or shallowly lobed; 4–25 mm long; 1.5–22 mm wide. Stamens 8; filaments glabrous. Anthers 0.3–2.2 mm long. Nectaries present (sometimes inconspicuous). Gynoecia inferior. Carpels syncarpous; 4. Ovaries glabrous, or hairy; puberulent, or pubescent, or tomentose. Ovary hairs sparse, or dense; white, or translucent. Styles 1. Styles straight; basal portion smooth, or with hairs at the base. Stigmas per style 1, or 4; broad-cylindrical, or strap-like lobes, or receptive surface at the end of an otherwise unmodified style. Placentation axile. Ovules numerous. Fruit stalked; stalk 5–40 mm long. Fruit dry; a capsule; elongate-cylindrical; not distinctly flattened; dehiscent; splitting to the base into separate segments; teeth 4. Fruit 20–70 mm long; 1–3.5 mm wide; black, or brown, or red, or purple, or straw coloured; hairy; surface appearing veinless. Seeds numerous; 0.8–2 mm long; brown, or yellowish; with surfaces smooth, or ridged.
Chromosome information. 2n = 18, 36, 54, 72.
Notes. The name of the genus Epilobium derives from the Greek
words epi (upon) and lobos (a pod), a reference to the relatively
advanced (evolutionarily) position of the floral parts on top of the young,
pod-like ovary.
Baum, Sytsma and Hoch (1994) published a phylogenetic
analysis of Epilobium based on sequences of the ITS regions and the 5.8S
cistron of nuclear ribosomal DNA. They found that section Chamaenerion
(which includes our Chamerion [Epilobium] angustifolium and C. [E.]
latifolium) was sister to the rest of the genus. Holub (1972) had previously
argued that the nine species in this group were easily morphologically
distinguishable and supported treating it as a separate genus. He presented
evidence that the name Chamaenerion (although long used for this group)
was illegitimate and he published the new combinations with Chamerion.
Based on this and other studies, Peter C. Hoch, Missouri Botanical Garden, is
preparing a paper that presents the morphological and molecular data for the
family. In September 2001 this work was tied up in an on-going "tribal"-level
analysis, using some new DNA sequences that were expected to provide evidence at
a more fine-grained level. It was expected to be finished within a year, and the
treatment of this group for FNA is to be based on the monograph that he is in
the process of finishing now. In this treatment it is anticipated that
Chamerion will be treated as a separate genus (Peter Hoch, personal
communication). We follow this treatment here, and use the names Chamerion
angustifolium and C. latifolium for the fireweeds.
The
distribution of the Onagraceae in Greenland was mapped by Fredskild (1985).
Orel (1977) discussed the taxonomic rank of the genera Epilobium and
Chamaenerion in the Family Onagraceae on the basis of investigating the
pollen and the pore openings.
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).