Polystichum omeiense C. Christensen 1906

Polystichum omeiense C. Christensen (1906: 67), cons. prop. (Fig. 5.) Basionym: — Aspidium caruifolium Baker (1888: 228) ≡ Polystichum caruifolium (Baker) Diels (1900: 194). TYPE:— CHINA. Sichuan province: Mt. Emei (Mount Omei), 3000–8000 ft, December 1887, E. Faber 1027 (holotype K001040166!; isotypes MO-255603!, NY00128113!). Main characters (based on N. T.Lu 35_HG2021): Petiole scales not appressed; lamina tripinnate, narrowly elliptic or broadly elliptic-lanceolate, middle or upward broadest; pinnae approximate, about 28 pairs, pinnae below narrowed gradually toward lamina base; ultimate lobes linear; rachis scales ovate or lanceolate. Notes:— This species is easily identifiable, as there are only two species in Polystichum with linear ultimate lobes: P. alcicorne (Baker 1888: 229) Diels (1900: 194) and P. omeiense. These linear-leaved species were both described in 1888 from China. The Vietnamese material of P. omeiense was not collected until 2021. It was first discovered in the Bat Dai Son’s Cave where there were only few individuals. It’s conservation in Vietnam needs attention. Polystichum omeiense is a member of P. sect. Sphaenopolystichum Ching ex W.M.Chu & Z.R.He in Kung et al. (2001: 223), a section with 13 species known so far (Zhang & Barrington 2013, Wang et al. 2022). There are three members in Vietnam: P. auriculum Ching (1949: 309), P. omeiense, and P. tonkinense (Christ in Christ & Billet 1898: 268) W.M.Chu & Z.R.He in Kung et al. (2001: 169). The name Polystichum omeiense was proposed for conservation against P. caruifolium in our earlier study (Lu et al. 2017). Additional specimens examined:— VIETNAM. Ha Giang Province: Dong Van District, Ta Lung commune, Ha Chua La Village, inside a cave, June 2021, Ngan T. Lu 35_HG2021 (VNMN!). CHINA. Sichuan Province: Emei mountain, 02 September, 2014, Xiao-Jie Li s.n. (CSH05680!).Published as part of Lu, Ngan Thi, Zhang, Liang, Thanh, Nguyen Trung, Toan, Le Chi & Zhang, Li-Bing, 2023, Three new species and one new record of the fern genus Polystichum (Dryopteridaceae) from Vietnam, pp. 85-94 in Phytotaxa 607 (1) on pages 91-92, DOI: 10.11646/phytotaxa.607.1.7, http://zenodo.org/record/821224