Lemmon’s holly fern (Polystichum lemmonii) COSEWIC assessment and status report: chapter 3

Species Information

Name and classification

Scientific name:

Polystichum lemmonii Underw.

Synonym:

  • Polystichum mohrioides auct. non (Bory) C. Presl.
  • Polystichum mohrioides (Bory) C. Presl. var. lemmonii (Underw.) Fern.

Common name:

Lemmon’s holly fern

Family:

Dryopteridaceae

Major plant group:

fern

Description

Lemmon’s holly fern, Polystichum lemmoniiUnderw.Footnote1, is a member of a cosmopolitan genus of over 175 species (Smith and Lemieux 1993). It is one of eight Polystichum species occurring in British Columbia (Ceska 2000; Douglas et al. 2002b) and nine occurring in Canada (Cody and Britton 1989; Wagner 1993). Generally, American authors treated P. lemmonii as a synonym of P. mohrioides (Bory) C. Presl. until Wagner (1979) demonstrated that the North American plant was different from the South American plant. Polystichum lemmonii was first recorded in Canada by Cody and Britton (1984). The absence of earlier records in Canada prior to 1984 likely reflects the lack of botanical fieldwork on these ridges consisting of a relatively depauperate flora. The species’ occurrence on two nearby ridges would indicate that it has been present for some time allowing it to spread from what was likely a single long distance dispersal event.

Polystichum lemmonii is an evergreen, perennial, tufted fern arising from a short, stout rhizome (Figure 1; Ceska 2000). The decumbent to ascending fronds are 10-40 cm long, 3-7 cm wide and 2-pinnate. The 20-35 pinnae on each side of the rachis are ovate with rounded pinnules. The ultimate segments are entire or weakly toothed. The round sori are attached near the midvein with entire or minutely toothed indusia.

In British Columbia, P.lemmonii may be confused with either Kruckeberg’s holly fern (P. kruckebergii) or Mountain holly fern (P. scopulinum). It may be distinguished from the latter two species by the lack of spines on the teeth of the ultimate segments of the pinnae (Hitchcock et al. 1969; Wagner 1993; Ceska 2000).

Figure 1. Illustration of Polystichum lemmonii. (Courtesy of University of Washington Press.)

Figure 1.  Illustration of Polystichum lemmonii.  (Courtesy of Universityof WashingtonPress.)

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