Brachiolejeunea laxifolia (T.Taylor) Schiffn.

  • Authority

    Gradstein, S. Robbert. 1994. Lejeuneaceae: Ptychantheae, Brachiolejeuneae. Fl. Neotrop. Monogr. 62: 216. (Published by NYBG Press)

  • Family

    Lejeuneaceae

  • Scientific Name

    Brachiolejeunea laxifolia (T.Taylor) Schiffn.

  • Type

    Type. Ecuador. Mt. Pichincha, Jameson s.n. (holotype, FH-TAYL; isotype, BM).

  • Synonyms

    Phragmicoma laxifolia Taylor, Thysananthus mexicanus Taylor, Brachiolejeunea mandoni Steph., Brachiolejeunea uleana Steph., Lejeunea latifolia Herzog

  • Description

    Species Description - Paroicous. Plants 2-5 cm long × 1.7-2.5 mm wide, olive green when alive, becoming light to dark brown when dry. Stems 0.15-0.2 mm in diam., in cross section composed of ca. 15-25 epidermal cells surrounding 30-60(-80) medullary cells; ventral merophyte 4-6(-8) cell rows wide; dorsal side of the stem with a (l-)2-4 cells high ridge. Leaves laxly imbricate, convex to subsquarrose when moist, lobe ovate-falcate, 1-1.4 × 0.6-0.9 mm, apex narrowly obtuse to apiculate, ventral margin when spread out forming an angle of 90-125° with the keel; median cells 25-45 × 17-28 µm; oil bodies homogeneous, ellipsoid-fusiform, 5-7 µm long, 16-27 per cell, in stem cells smaller and more numerous. Lobules broadly ovate-triangular, ca. 0.3-0.45 mm long, l/3-2/5× lobe length, apex oblique, short continuing into the ventral leaf margin, keel curved, free margin plane and straight, usually with 3-4 regularly spatiated teeth, teeth 2-3 cells long, upper cell inflexed. Underleaves subimbricate, orbicular, 0.5-0.7 mm long, ca. 3× stem width, margins plane or narrowly recurved, bases distinctly folded, insertion line deeply arched, 0.15-0.2 mm deep. Gynoecia with two innovations (exceptionally only one), bracts narrowly winged along the keel, lobule ca. l/2× lobe length. Perianths up to 2 mm long, exserted to 1/2-2/3, beak 5-6 cells long. Sporophyte: spores rectangular, 70-105 µm long, without rosettes; elaters 320-470 µm long.

  • Discussion

    Chemistry: two sesquiterpene alcohols, three oxygenated sesquiterpenoids and the flavonoid luteolin-7-O-glucoside have been detected as major constituents of this species (Gradstein et al., 1981, 1988).

    Brachiolejeunea laxifolia is recognized by its 3-4-dentate lobule, the distinct longitudinal ridge or "lamellate paraphyllium" on the dorsal side of the stem (van Slageren & Gradstein, 1981), and the constant presence of two innovations. The species is paroicous but the androecia are easily overlooked as the male bracts are almost identical to vegetative leaves and the antheridia vanish as soon as the gynoecium matures. To observe the antheridia, leaves of young innovations should be examined.

    The species is closely related to B. leiboldiana and the two may be confused. For differences see under the latter. Brachiolejeunea laxifolia may grow together with Blepharolejeunea securifolia and B. incongrua, which are habitually rather similar but have a very different lobule. Blepharolejeunea incongrua also has a very characteristic, short obconical brownish perianth with sharp lateral keels. The perianth of B. securifolia, however, is almost identical to that of B. laxifolia. Differences between the two species are discussed under Blepharolejeunea securifolia.

    Brachiolejeunea laxifolia varies somewhat in size and, as in many other liverwort species, plants tend to become bigger with increasing altitude. Innovations are normally paired but single innovations have been observed in material from the Dominican Republic (Buck 7823).

  • Distribution

    Throughout the cordilleras of Central and tropical South America, at elevations ranging from (1500-)2000 to 3500 m; also at high altitudes in the Greater Antilles (Jamaica, Dominican Rep.) and in SE Brazil. Brachiolejeunea laxifolia is particularly common in the high Andes and grows on bark and rock, occasionally on leaves, in rather open habitats: forest edges, scrubby vegetations, etc.

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