Polystichum acrostichoides |
Polystichum kruckebergii |
|
---|---|---|
Christmas fern, polystic faux-acrostic |
holly fern, Kruckeberg's holly fern, Kruckeberg's sword fern, Kruckeberg's sword fern fern |
|
Stems | erect. |
ascending. |
Leaves | dimorphic (only in this species); fertile pinnae distal, much contracted; sterile leaves arching, 3–8 dm; bulblets absent. |
erect, 1–2.5 dm; bulblets absent. |
Petiole | 1/4–1/3 length of leaf, densely scaly; scales light brown, diminishing in size distally. |
1/10–1/5 length of leaf, sparsely scaly; scales light brown, gradually diminishing in size distally. |
Blade | linear-lanceolate, 1-pinnate; base narrowed. |
linear, 1-pinnate-pinnatifid, base narrowed. |
Pinnae | oblong to falcate, not overlapping, in 1 plane, 2–6 cm; base oblique, acroscopic auricles well developed; margins serrulate-spiny with teeth ascending; apex acute or blunt with subapical and apical teeth same size; microscales filiform, lacking projections, dense, on abaxial surface only. |
rhombic-ovate to short-falcate, proximal pinnae ± triangular; pinnae overlapping, twisted somewhat out of plane of blade, 0.5–1.5 cm; base oblique, acroscopic auricle well developed; margins shallowly incised to merely dentate or serrulate, teeth spreading and spiny at tip; apex acute with subapical and apical teeth same size; microscales lanceolate with few projections, confined to costa, on abaxial surface only. |
Indusia | entire. |
|
Sori | confluent, completely covering abaxial surface of pinnae (only in this species); indusia entire. |
|
Spores | light brown. |
dark brown. |
2n | = 82. |
= 164. |
Polystichum acrostichoides |
Polystichum kruckebergii |
|
Habitat | Forest floor and shady, rocky slopes | Rocks and cliffs in subalpine to alpine habitats |
Elevation | 0–1500 m (0–4900 ft) | 1500–3200 m (4900–10500 ft) |
Distribution |
AL; AR; CT; DC; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; NE; NH; NJ; NY; OH; OK; PA; RI; SC; TN; TX; VA; VT; WI; WV; NB; NS; ON; PE; QC; Mexico; naturalized in Europe
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CA; ID; MT; NV; OR; UT; WA; BC
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Discussion | Polystichum acrostichoides is a common species most closely related to P. munitum (G. Yatskievych et al. 1988), which also occurs extensively on forest floors. The dimorphic pinnae of Polystichum acrostichoides are not unique to the genus; they are found also in some Asian species. Numerous variants have been named, mostly as forms, but none are of taxonomic consequence. Hybrids are known with P. braunii (P. × potteri Barrington) and P. lonchitis (P. × hagenahii Cody). The latter hybrid is rare, known only from its type locality in Ontario, where it grows with both parents. It is recognized by its intermediate morphology (leaves wider than P. lonchitis, narrower than P. acrostichoides, with slightly contracted sorus-bearing pinnae) and malformed sporangia and spores. Polystichum × potteri is much more widespread, from Nova Scotia, New Brunswick, and Quebec through New England to Pennsylvania. It resembles P. braunii but has narrower leaves bearing malformed sporangia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Polystichum kruckebergii is widely but sporadically distributed in small numbers in both the Sierra-Cascade and Rocky Mountain systems. Populations sometimes consist of only two or three dwarfed plants that are difficult to distinguish from P. scopulinum, with which they may occur. The spreading teeth of equal size at the pinna apex will usually distinguish this species. Polystichum kruckebergii is a tetraploid presumed to be of hybrid origin, with P. lonchitis and P. lemmonii as its diploid progenitors (W. H. Wagner Jr. 1973), although this hypothesis has not been confirmed. The hybrid with P. munitum has been found in Washington (P. S. Soltis et al. 1987) with both parents, and it is distinguished by intermediate morphology and abortive sporangia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 2. | FNA vol. 2. |
Parent taxa | Dryopteridaceae > Polystichum | Dryopteridaceae > Polystichum |
Sibling taxa | ||
Synonyms | Nephrodium acrostichoides | |
Name authority | (Michaux) Schott: Gen. Fil. plate 9. (1834) | W. H. Wagner: Amer. Fern J. 56: 4. (1966) |
Web links |
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