Lastreopsis

  • Authority

    Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.

  • Family

    Dryopteridaceae

  • Scientific Name

    Lastreopsis

  • Description

    Genus Description - Terrestrial, rarely epiphytic; rhizomes short- to long-creeping or suberect, scaly; fronds monomorphic, clumped; stipes scaly at base, with two prominent ridges adaxially, the channel between ridges with abundant short, erect, ctenitoid hairs (short, articulate, unbranched, catenate, hyaline to reddish hairs), rachises with similar channels continuous with channels of costae, ridges continuous with thickened margin of ultimate segments; blades firm-herbaceous, (2–)3–5-pinnate, pentagonal, proximal pinnae more developed basiscopically in many species (ours), pinnae catadromous, apices pinnatifid; indument of adpressed glandular hairs on abaxial blade surfaces; buds present near apices of rachises or costae in many species (ours); veins free, readily visible on both sides, simple or forking, ending before the blade margins; sori usually round, indusiate or exindusiate, indusia roundreniform; sporangia often with 1–2 stalked glands on sporangial pedicels or within sori; spores bilateral with cristate perispore; x=41.

  • Discussion

    Type: Lastreopsis recedens (J. Sm. ex T. Moore) Ching [= Lastrea recedens J. Sm. ex T. Moore] [= Lastreopsis tenera (R. Br.) Tindale].

    Polystichum sect. Parapolystichum Keyserl., Polyp. Herb. Bunge. 11, 45. 1873. Parapolystichum (Keyserl.) Ching, Sunyatsenia 5: 239. 1940. Type: Parapolystichum effusum (Sw.) Ching [= Polypodium effusum Sw.] = Lastreopsis effusa (Sw.) Tindale.

    Lastreopsis is a pantropical genus of about 36 species of southtemperate and rain forest regions, of which five to six are American; only two species, both wide-ranging, occur in Mexico. Species are most numerous in the Australasian area, especially Australia, with 15 species (Jones in McCarthy, 1998). The genus is often said to be closest to Ctenitis, which has similar (but not identical) hairs and very dissected fronds. However, the configuration of the ridges on the minor axes and rachises in Lastreopsis is distinctive; in Ctenitis such ridges are lacking or, if present, they are interrupted and not decurrent onto the axes above or below. Preliminary molecular data place Lastreopsis within the large dryopteroid clade, perhaps allied to Megalastrum and Rumohra more closely than to Ctenitis (Cranfill, unpubl. data).