Epilobium densiflorum
Onagraceae tribe Epilobieae
dense boisduvalia, dense spike-primrose, dense willowherb, dense-flower spikeprimrose, dense-flower willowherb, willow herb
erect or ascending, terete, 4–150 cm, simple or branched with strong central axis, proximal branches ascending or suberect, villous or strigillose, often mixed glandular puberulent distally.
opposite and often early-deciduous proximally, alternate and crowded distally, usually subsessile, rarely petiole 1–2 mm, blade usually narrowly lanceolate to sublinear, rarely to lanceolate, 1.4–7.5(–9.2) × 0.5–1.4 cm, base cuneate to attenuate, margins remotely to sharply serrulate, 5–12 teeth per side, lateral veins obscure, 2–5 per side, apex acute, surfaces densely villous and/or strigillose;
bracts broader than cauline leaves, broadly lanceolate to ovate or subrotund, 0.5–2.5 × 0.3–1.8 cm, long-acuminate, sometimes folded on midrib.
opposite at least near base or throughout, alternate distally, or sometimes alternate throughout;
stipules absent.
erect spikes, congested, simple, densely villous and strigillose, sometimes mixed glandular puberulent.
erect, often hidden within subtending bracts, usually chasmogamous;
buds sessile, narrowly elongate, 2–4 mm;
floral tube 1.3–3.8 × 1–2.2 mm, ring of hairs 0.6–2 mm distal to base inside;
sepals 2–7.5 × 0.5–2.2 mm, apex acute;
petals rose-purple, magenta, pink, or white, 3–9.5(–11.5) × 1.2–5(–6.2) mm, apical notch 0.8–3.8 mm;
filaments dark pink, those of longer stamens 1.5–4.5 mm, those of shorter ones 0.5–1.9 mm;
anthers yellow, 0.5–1.2 × 0.3–0.7 mm;
ovary 2–5 mm, densely villous, often mixed glandular puberulent;
style white, 2.2–5.5(–7.5) mm, glabrous, stigma subcapitate to irregularly 4-lobed, 0.3–0.8 × 0.3–1 mm, surrounded by longer anthers.
actinomorphic or slightly zygomorphic, 4-merous;
sepals erect or spreading;
stamens 2 times as many as sepals;
pollen shed in tetrads or monads.
a slender, cylindrical, loculicidal capsule.
cylindrical to subfusiform, 4–11 mm, beak to 0.5 mm, central column persistent, surfaces densely villous;
subsessile or pedicel 1–2.5 mm.
3–8 per locule, irregularly angular-fusiform, 1.2–1.6(–1.9) × 0.4–1 mm, without a chalazal collar, light brown, surface irregularly reticulate with raised cells.
(1 or) many per locule, with tuft of hairs (coma) at chalazal end, sometimes without coma.
= 20.
Epilobium densiflorum
Onagraceae tribe Epilobieae
Epilobium densiflorum is an extremely variable species that changes its aspect through the flowering season. Collections made very early in the season may include only well-spaced, narrowly lanceolate leaves, the proximal ones usually opposite, and a short, sparse, somewhat open inflorescence. A late-season collection, even from the same population, may entirely lack cauline leaves, and consist instead of bare, peeling stems topped by dense, tightly imbricate-bracted inflorescences, with each broad bract enclosing a capsule or flower.
Boisduvalia douglasii Spach is an illegitimate substitute for Oenothera densiflora Lindley and pertains here.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Genera 2, species 173 (2 genera, 43 species in the flora).
Epilobium and its close relatives have been recognized historically either as part of Onagreae (A. P. de Candolle 1828b), sometimes as a subtribe (É. Spach 1834–1848, vol. 4; J. Torrey and A. Gray 1838–1843, vol. 1), or as the distinct Epilobieae (R. Raimann 1893; P. A. Munz 1965; P. H. Raven 1976). The synapomorphies for Epilobieae as currently delimited include its highly condensed, heteropycnotic chromosomes with a base chromosome number of x = 18, sepals held erect or spreading (not reflexed) throughout anthesis, and the presence of a coma of hairs on the seeds (secondarily lost in some species). Molecular support for the tribe is strong (97–100% BOOTSTRAP support; D. A. Baum et al. 1994; R. A. Levin et al. 2004).
Endlicher established Epilobieae and included Oenothera within it; it is unclear how or whether his concept differed from Onagreae of A. P. de Candolle (1828b). É. Spach (1834–1848, vol. 4) recognized these genera as Onagreae and differentiated so-called sect. Oenotherinae from sect. Epilobieae, placing in the latter not only Epilobium and related groups, but also Clarkia and its segregates. J. Torrey and A. Gray (1840) excluded Clarkia from their Epilobiinae and also excluded Boisduvalia, a delimitation also followed by R. Raimann (1893) for his Epilobieae. Epilobieae did not assume its current delimitation, including only Epilobium and its close relatives, until the works of P. A. Munz (1941) and P. H. Raven (1964).
G. L. Stebbins (1971) and P. H. Raven (1976) considered the diverse chromosome numbers in Epilobieae and proposed that the species of Boisduvalia (now a section of Epilobium) with n = 9 or 10 represented the original base chromosome number for the tribe, and that these numbers were derived from x = 11 which is found in Circaeeae, Gongylocarpeae, and Lopezieae (W. L. Wagner et al. 2007). They proposed a series of aneuploid reductions from n = 9 or 10 to n = 6, followed by polyploidy to produce the array of numbers in Epilobium (n = 12, 13, 15, 16, 18, 30) and Boisduvalia (n = 9, 10, 15, 19). D. A. Baum et al. (1994) demonstrated that molecular data did not support that hypothesis and found that a monophyletic Chamaenerion (n = 18, 36, 54) forms a strongly distinct sister branch to Epilobium, within which sect. Epilobium (n = 18) is monophyletic and sister to the rest of Epilobium, including the former segregates Boisduvalia and Zauschneria. The data from Baum et al. suggested that Epilobieae are primitively polyploid, with numbers based on x = 18, which is unique in the family. Using comparable sampling and some additional genes, R. A. Levin et al. (2004) found strong support for the phylogeny proposed by Baum et al.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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