Epilobium siskiyouense |
Epilobium densiflorum |
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Siskiyou fireweed, Siskiyou rock-fringe, Siskiyou willow-herb |
dense boisduvalia, dense spike-primrose, dense willowherb, dense-flower spikeprimrose, dense-flower willowherb, willow herb |
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Habit | Herbs ± suffruticose, shoots from woody caudex with barklike periderm extending to 40 cm below ground, shoots with scaly bases. | Herbs usually with taproot, sometimes with loose network of roots. |
Stems | several to many, erect to ascending, loosely clumped, terete, 10–25 cm, rarely branched distal to base, usually short-villous and strigillose throughout, mixed sparsely glandular puberulent distally, rarely subglabrous proximal to inflorescence. |
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. |
Leaves | opposite proximal to inflorescence, alternate and usually crowded distally, sessile; blade gray-green, narrowly to broadly ovate, 1.3–2.6 × 0.8–2 cm, base rounded to subcordate, margins usually serrulate, 6–12 teeth per side, rarely subentire, veins inconspicuous, 3–5 per side, apex rounded proximally to acute distally, surfaces sparsely short-villous to subglabrous and glaucous; bracts much reduced. |
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. |
Inflorescences | erect, compact racemes, densely canescent and glandular puberulent, or subglabrous, only ovaries pubescent. |
erect spikes, congested, simple, densely villous and strigillose, sometimes mixed glandular puberulent. |
Flowers | erect; buds often purplish green, 9–11 × 3.5–5 mm, blunt; pedicel 6–12 mm; floral tube 2.1–4 × 2.9–5 mm, prominent ring of tissue 0.3–0.6 mm wide, edged by spreading hairs, 0.9–1.8 mm from base of tube inside; sepals purplish green, 5–10.5 × 2–3.5 mm, apex acute; petals pink to rose-purple, obcordate, 10–22.5 × 9.5–15.5 mm, apical notch 2–6.5 mm; filaments cream, those of longer stamens 6.5–14 mm, those of shorter ones 3.5–11 mm; anthers cream 1.9–3.3 × 0.7–1.2 mm; ovary 12–22 mm, ± densely canescent and glandular puberulent; style white to light pink, 10.5–18 mm, sparsely villous just proximal to stigma, stigma broadly 4-lobed, 1–1.8 × 2.4–4.2 mm, exserted beyond anthers. |
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. |
Capsules | 25–45 mm, surfaces canescent and glandular puberulent; pedicel 6–25 mm. |
cylindrical to subfusiform, 4–11 mm, beak to 0.5 mm, central column persistent, surfaces densely villous; subsessile or pedicel 1–2.5 mm. |
Seeds | narrowly obovoid, 1.4–1.9 × 0.6–0.7 mm, with low, obscure chalazal collar, light brown, surface papillose; coma easily detached, somewhat tawny, 4–8 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. |
2n | = 36. |
= 20. |
Epilobium siskiyouense |
Epilobium densiflorum |
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Phenology | Flowering Jul–Aug. | Flowering May–Oct. |
Habitat | Stream banks, moist, rocky slopes, montane ridges, sometimes on serpentine areas. | Vernally wet places, moist pastures, woodlands, meadows, along streams and ditches, alluvial valleys, often on low ground in volcanic or sandy soils. |
Elevation | 1600–2500 m. [5200–8200 ft.] | 0–2600 m. [0–8500 ft.] |
Distribution |
CA; OR
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AZ; CA; ID; MT; NV; OR; UT; WA; BC; Mexico (Baja California)
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Discussion | Epilobium siskiyouense is endemic to the Klamath region in southwestern Oregon (Jackson County) and north-central California in the Salmon, Scott Bar, and Siskiyou mountains of Siskiyou and Trinity counties. As noted by Hoch and Raven, this geographical range and several morphological features appear to be intermediate between those of E. obcordatum and E. rigidum. All three species have unusually large flowers (12–26 mm) with four-lobed stigmas, and as a group are quite distinct from their congeners in the region. Despite these similarities, the three taxa differ substantially in details of floral structure, especially regarding the dimensions of the floral tube. Specifically, E. rigidum has mean petal length 18.2 mm, floral tubes 1–1.6 × 2.5–3.6 mm; E. siskiyouense mean petal length 17.1 mm, floral tubes 2.1–4 × 2.9–5 mm; and E. obcordatum mean petal length 18.6 mm, floral tubes 3.2–5.2 × 2.2–3.6 mm. Thus, in flowers that are similar in overall size and aspect, E. rigidum has a very short, broad floral tube, E. obcordatum has a relatively long, narrow tube, and E. siskiyouense has a tube intermediate in size and shape. In terms of the ratio of tube length to width, the three taxa do not overlap. Although these characters are difficult to include in a key (since they require floral dissection and/or precise measurements), they are diagnostic for these species. Epilobium siskiyouense has an additional diagnostic floral character that is unique in the genus. Whereas most other species of Epilobium have a simple ring of spreading hairs, sometimes with a low ridge of tissue near the mouth of the floral tube, E. siskiyouense has a relatively broad ring of tissue (0.3–0.6 mm wide), shaped like a washer, from which spreading hairs arise; this feature may provide protection for the nectar. Epilobium siskiyouense has two distinct patterns of vestiture on the stems. In some specimens, the lower stems are mixed canescent and glandular puberulent and the inflorescence only glandular puberulent. In other specimens, the stems are subglabrous below a sparsely canescent and glandular puberulent inflorescence. There is no obvious correlation of this difference with any other morphological, ecological, or geographical factors. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 10. | FNA vol. 10. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | E. obcordatum subsp. siskiyouense, E. obcordatum var. laxum | Oenothera densiflora, Boisduvalia bipartita, B. densiflora, B. densiflora var. bipartita, B. densiflora var. imbricata, B. densiflora var. montana, B. densiflora var. pallescens, B. densiflora var. salicina, B. imbricata, B. salicina, B. sparsiflora, B. sparsifolia, O. densiflora var. imbricata |
Name authority | (Munz) Hoch & P. H. Raven: Madroño 27: 146. (1980) | (Lindley) Hoch & P. H. Raven: Phytologia 73: 457. (1993) |
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