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alpine willow-herb, pimpernel willow-herb, épilobe à feuilles de mouron

Hornemann's willow-herb, épilobe de Hornemann

Habit Herbs with spreading thin, small-leafed epigeous soboles to 5 cm. Herbs with short, scaly hypogeous or leafy epigeous soboles.
Stems

many, ascending, often sigmoidally bent, nodding distally, later erect, clumped or mat-forming, terete, 3–20(–25) cm, simple, subglabrous, sometimes with faint raised strigillose lines decurrent from margins of petioles, rarely mixed strigillose and sparsely glandular puberulent distally.

ascending to erect, clumped, terete, 10–45 cm, usually simple, rarely branched proximally, subglabrous proximal to inflorescence with sparsely strigillose lines decurrent from margins of petioles, ± sparsely mixed strigillose and glandular puberulent distally.

Leaves

opposite and crowded proximal to inflorescence, alternate distally, petioles 1–6 mm, rarely subsessile distally;

blade spatulate to oblong proximally, elliptic to narrowly lanceolate or sublinear distally, (0.5–)0.8–2.5 × 0.3–1 cm, base attenuate to cuneate, margins subentire proximally, sparsely denticulate distally with 2–5 low teeth per side, veins obscure, 2–4 per side, apex obtuse or rounded proximally to subacute distally, surfaces subglabrous;

bracts reduced, usually much narrower.

opposite proximal to inflorescence, usually alternate distally, petioles 3–9 mm proximally to subsessile distally;

blade broadly elliptic to spatulate proximally, ovate to lanceolate distally, ± coriaceous or not, 1.5–6.2 × 0.7–2.9 cm, base attenuate to cuneate or rounded, margins subentire proximally, denticulate distally with 10–25 teeth per side, veins often inconspicuous, 4–7 per side, apex obtuse to subacute, surfaces glabrous or, sometimes, strigillose along margins;

bracts reduced.

Inflorescences

nodding in bud, later suberect, few-flowered racemes, subglabrous to sparsely strigillose and/or glandular puberulent.

erect or nodding, open racemes, mixed strigillose and glandular puberulent.

Flowers

suberect;

buds 2–5 × 1–2 mm;

pedicel 1–6(–15) mm;

floral tube 0.6–1.2 × 0.8–1.8 mm, slightly raised subglabrous ring at mouth inside;

sepals green to reddish purple, 1.5–5 × 0.6–1.5 mm, abaxial surface subglabrous to sparsely glandular;

petals usually pink to rose-purple, rarely white, narrowly obcordate, (1.7–)2.5–6.5(–8) × 1.6–3.5 mm, apical notch 0.5–1.2 mm;

filaments cream to light pink, those of longer stamens 1.4–3.2 mm, those of shorter ones 0.7–2 mm;

anthers 0.3–0.6 × 0.2–0.4 mm;

ovary often reddish purple, 6–20 mm, subglabrous or sparsely strigillose and glandular puberulent;

style white, 1.2–2.5 mm, glabrous, stigma broadly clavate to subcapitate, entire, 0.9–1.5 × 0.4–0.7 mm, surrounded by longer anthers.

erect;

buds 2–5.5 × 2–4 mm;

pedicel 2–5 mm;

floral tube 1–2.2 × 1.3–2.8 mm, sparse ring of hairs at mouth inside or ring absent;

sepals sometimes red-tipped or bright red, 2–7 × 1–2.2 mm, abaxial surface sparsely strigillose and glandular puberulent;

petals usually rose-purple or magenta to light pink, rarely white, 3–10(–11) × 2–6 mm, apical notch 0.7–2.4 mm;

filaments cream to light pink, those of longer stamens 1.4–5(–6) mm, those of shorter ones 1.2–4 mm;

anthers light yellow, 0.4–1.2 × 0.3–0.6 mm;

ovary 15–25 mm, glandular puberulent, sometimes mixed strigillose;

style white or cream, 2–8 mm, stigma cream, clavate or cylindrical, entire, 1.2–3 × 0.5–1 mm, usually surrounded by, rarely exserted beyond, anthers.

Capsules

slender, often reddish purple, 17–40(–55) mm, surfaces subglabrous or with scattered hairs;

pedicel 5–35(–68) mm.

35–65 mm, surfaces glandular puberulent, sometimes mixed strigillose;

pedicel 5–15(–25) mm.

Seeds

narrowly obovoid, 0.7–1.4 × 0.3–0.5 mm, inconspicuous chalazal collar 0.1–0.2 mm wide, light brown, surface reticulate (smooth);

coma persistent, dull white, 2–4 mm.

narrowly fusiform or oblanceoloid, 0.9–1.6 × 0.3–0.5 mm, chalazal collar short, 0.05–0.1 mm, blond to brown, surface distinctly papillose or reticulate/smooth;

coma readily detached, dingy white, 6–11 mm.

2n

= 36.

Epilobium anagallidifolium

Epilobium hornemannii

Phenology Flowering Jun–Sep.
Habitat Moist flats, stream banks, subarctic coastal marsh edges, high montane and alpine meadows and seeps.
Elevation 0–4500 m. [0–14800 ft.]
Distribution
from FNA
AK; CA; CO; ID; ME; MT; NH; NV; OR; UT; WA; WY; AB; BC; NL; NT; NU; QC; YT; Greenland; Eurasia
[WildflowerSearch map]
[BONAP county map]
from USDA
North America; Eurasia
[WildflowerSearch map]
[BONAP county map]
Discussion

Epilobium anagallidifolium is widely but sparsely distributed in high montane-alpine and subarctic Eurasia, including Europe, Russia, China, and Japan.

Epilobium anagallidifolium usually forms low clumps or mats, with stems nodding in bud and usually subglabrous below the inflorescence. Many collections of E. anagallidifolium from eastern Canada and Greenland tend to be unusually tall (to 25 cm) and robust for the species, with somewhat larger, thicker leaves, and longer pedicels (to 60 mm). Similarly large and robust specimens occur scattered in Yukon and Washington, and may result from occasional hybridization and introgression with sympatric species such as E. hornemannii or E. lactiflorum, which also have the CC chromosomal arrangement. In an analysis of Fennoscandian populations of the Alpinae group, I. Kytövuori (1972) found a similar pattern of mostly smaller, sigmoidal plants of E. anagallidifolium with a small proportion of larger ones, and he also suggested the possibility of hybridization and/or introgression.

Plants of Epilobium anagallidifolium, and indeed of the whole Alpinae group, from Haida Gwaii (the Queen Charlotte Islands) of British Columbia (J. A. Calder and R. L. Taylor 1968), are particularly distinctive compared to those on the mainland, and difficult to interpret. The observed differences may be the result of hybridization with other sympatric species or a response to unique ecological conditions on the islands, reinforced by relative isolation from mainland British Columbia.

The Linnaean name Epilobium alpinum has long been a source of nomenclatural confusion and instability, since it circumscribed at least four distinct species, especially E. anagallidifolium. A proposal by P. C. Hoch et al. (1995) to permanently reject the name E. alpinum Linnaeus was approved.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Subspecies 2 (2 in the flora).

Epilobium hornemannii occurs widely in montane and boreal regions in North America and western Eurasia, and also in Japan and the Russian Far East. It is characterized by having the CC chromosome arrangement and is included in the Alpinae alliance with E. anagallidifolium, E. lactiflorum, and others (I. Kytövuori 1972).

W. Trelease (1891) discussed eastern and western forms of Epilobium hornemannii, the latter divided into two variations; however, he did not formally recognize any of these variants.

P. A. Munz (1965) included the Eurasian Epilobium alsinifolium Villars in his North American treatment, noting that it occurred in Greenland. However, B. Fredskild (1984) suggested that, for the most part, these determinations represent misidentifications of E. hornemannii.

The two subspecies recognized here intergrade throughout much of their shared range, but whereas subsp. hornemannii is commonly found in high montane to alpine regions, in the northern part of its range it grows at much lower elevations, and in maritime areasis replaced by coriaceous-leaved forms here designated as subsp. behringianum. The situation is rather analogous to the pattern seen in E. ciliatum in which subsp. ciliatum is wide-ranging and variable, but replaced in Pacific maritime areas by subsp. watsonii, from which it differs consistently in most specimens, but sometimes intergrades.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Parent taxa Onagraceae > subfam. Onagroideae > tribe Epilobieae > Epilobium > sect. Epilobium Onagraceae > subfam. Onagroideae > tribe Epilobieae > Epilobium > sect. Epilobium
Sibling taxa
E. arcticum, E. brachycarpum, E. campestre, E. canum, E. ciliatum, E. clavatum, E. cleistogamum, E. coloratum, E. davuricum, E. densiflorum, E. densum, E. foliosum, E. glaberrimum, E. hallianum, E. hirsutum, E. hornemannii, E. howellii, E. lactiflorum, E. leptocarpum, E. leptophyllum, E. luteum, E. minutum, E. mirabile, E. montanum, E. nevadense, E. nivium, E. obcordatum, E. obscurum, E. oreganum, E. oregonense, E. pallidum, E. palustre, E. parviflorum, E. rigidum, E. saximontanum, E. septentrionale, E. siskiyouense, E. smithii, E. suffruticosum, E. torreyi
E. anagallidifolium, E. arcticum, E. brachycarpum, E. campestre, E. canum, E. ciliatum, E. clavatum, E. cleistogamum, E. coloratum, E. davuricum, E. densiflorum, E. densum, E. foliosum, E. glaberrimum, E. hallianum, E. hirsutum, E. howellii, E. lactiflorum, E. leptocarpum, E. leptophyllum, E. luteum, E. minutum, E. mirabile, E. montanum, E. nevadense, E. nivium, E. obcordatum, E. obscurum, E. oreganum, E. oregonense, E. pallidum, E. palustre, E. parviflorum, E. rigidum, E. saximontanum, E. septentrionale, E. siskiyouense, E. smithii, E. suffruticosum, E. torreyi
Subordinate taxa
E. hornemannii subsp. behringianum, E. hornemannii subsp. hornemannii
Key
1. Leaves not coriaceous, petioles 3–7 mm proximally; sepals 2–4.5 mm; petals 3–9 mm; capsules 40–65 mm; seeds 0.9–1.2 mm, surface papillose.
subsp. hornemannii
1. Leaves ± coriaceous, petioles 4–9 mm proximally; sepals 5–7 mm; petals 8–10(–11) mm; capsules 35–55 mm; seeds 0.9–1.6 mm, surface reticulate.
subsp. behringianum
Synonyms E. alpinum, E. pseudoscaposum E. nutans
Name authority Lamarck in J. Lamarck et al.: Encycl. 2: 376. (1786) Reichenbach: Iconogr. Bot. Pl. Crit. 2: 73. (1824) — (as hornemanni)
Source FNA vol. 10. Treatment author: Peter C. Hoch. FNA vol. 10. Treatment author: Peter C. Hoch.
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