Epilobium siskiyouense |
Epilobium lactiflorum |
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Siskiyou fireweed, Siskiyou rock-fringe, Siskiyou willow-herb |
milk-flower willowherb, white-flower willow-herb, épilobe à fleurs blanches |
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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 with short, leafy epigeal soboles. |
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. |
ascending to suberect, often clumped, terete, 15–50 cm, usually simple, rarely branched proximally, subglabrous proximal to inflorescence except for raised densely strigillose lines decurrent from margins of petioles, usually mixed strigillose and 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 proximal to inflorescence or just proximal 1/3, alternate distally, petiole 3–12 mm, ± winged; blade broadly spatulate to ovate proximally, narrowly ovate to narrowly lanceolate distally, 2–5.5 × 0.8–2.4 cm, base attenuate to cuneate, margins subentire proximally to denticulate distally with 7–16 teeth per side, more marked distally, lateral veins inconspicuous, 4–8 per side, apex obtuse proximally to subacute distally, surfaces glabrous except for strigillose margins; bracts reduced and narrower. |
Inflorescences | erect, compact racemes, densely canescent and glandular puberulent, or subglabrous, only ovaries pubescent. |
nodding in bud, later erect, ± open racemes, mixed strigillose and 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. |
suberect; buds 2–5 × 1.5–3.5 mm; pedicel 5–15 mm; floral tube 1–2.2 × 1–3 mm, inner surface glabrous without ring; sepals often flushed purplish red, frequently keeled, (2–)3–5.5 × 0.9–1.8 mm, abaxial surface sparsely glandular puberulent, sometimes mixed strigillose; petals white, rarely with red veins or flushed light pink, 3–8.5 × 1.6–4.5 mm, apical notch 0.7–1.4 mm; filaments white to cream, those of longer stamens 1.4–4 mm, those of shorter ones 1.1–3 mm; anthers light yellow, 0.4–0.9 × 0.3–0.6 mm; ovary 20–40 mm, glandular puberulent; style cream or white, 1.4–4.6 mm, stigma clavate or rarely subcapitate and indented apically, entire, 1.2–2.5 × 0.4–1.6 mm, surrounded by anthers. |
Capsules | 25–45 mm, surfaces canescent and glandular puberulent; pedicel 6–25 mm. |
slender, sometimes flushed reddish green, ± ascending, 50–100 mm, surfaces sparsely glandular puberulent; pedicel 15–45 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. |
narrowly obovoid, 1.1–1.7 × 0.4–0.6 mm, chalazal collar 0.05–0.1 mm, blond or light brown, surface reticulate or sometimes barely rugose; coma easily detached, white, 7–14 mm. |
2n | = 36. |
= 36. |
Epilobium siskiyouense |
Epilobium lactiflorum |
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Phenology | Flowering Jul–Aug. | Flowering Jun–Sep. |
Habitat | Stream banks, moist, rocky slopes, montane ridges, sometimes on serpentine areas. | Montane stream banks, moist crevices and ledges, gravelly roadsides, burned-over woodlands, sandy moraines, subalpine forests, alpine meadows. |
Elevation | 1600–2500 m. [5200–8200 ft.] | 50–3800 m. [160–12500 ft.] |
Distribution |
CA; OR
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AK; AZ; CA; CO; ID; ME; MT; NH; NM; NV; OR; UT; VT; WA; WY; AB; BC; NB; NL; NS; NT; ON; QC; YT; Greenland; Eurasia
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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 lactiflorum has a nearly circum-subarctic distribution in North America (including coastal Greenland) and Eurasia, extending south into alpine and cool montane habitats along mountain axes. This distribution is similar to that of E. anagallidifolium and E. hornemannii (all with CC chromosomal arrangement), and these species commonly grow in similar habitats as well. Petal color can be variable in many Epilobium species, but E. lactiflorum (white flowers) differs quite consistently from E. hornemannii (rose-purple to light pink or rarely white) in that feature. Mature fruits and pedicels are also fairly longer in E. lactiflorum. Despite their morphological similarities and broadly overlapping ranges and habitats, E. lactiflorum and E. hornemannii subsp. hornemannii do not appear to hybridize with much frequency, although intermediates, with only moderately reduced seed fertility, might be difficult to detect. (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 | E. alpinum var. lactiflorum, E. canadense, E. canadense var. albescens, E. hornemannii var. lactiflorum |
Name authority | (Munz) Hoch & P. H. Raven: Madroño 27: 146. (1980) | Haussknecht: Oesterr. Bot. Z. 29: 89. (1879) |
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