Thuidium delicatulum (Hedw.) Schimp. var. delicatulum

  • Authority

    Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part Two: Orthotrichales to Polytrichales. Mem. New York Bot. Gard. 69 (2)

  • Family

    Thuidiaceae

  • Scientific Name

    Thuidium delicatulum (Hedw.) Schimp. var. delicatulum

  • Description

    Species Description - Rather robust, green or yellowish plants. Stems spreading or arched-ascending, 2-pinnate and ± frondose; paraphyllia very abundant (especially on stems and primary branches), polymorphous but mostly filiform and branched, the papillae not restricted to cell ends, the terminal cell with several rather small papillae. Stem leaves appressed when dry, erect-spreading when moist, 0.6-1.4 mm long, triangular-ovate, gradually or abmptly narrowed to a broad acumen, not particularly phcate; margins papillose-serrulate, revolute from the base to the acumen; costa ending in the acumen well below the apex; upper cells irregularly oblong-hexagonal, 6-10 x 8-12 µm, moderately incrassate, coarsely unipapillose at back. Leaves of primary branches erect-spreading, up to 0.5 mm long, acute; costa 1/2-2/3 the leaf length; cells 6-8 x 8-12 µm, rhombic, incrassate, stoutly unipapillose at back, the papillae 4-12 µm high, curved and often ± forked, the apical cell tmncate and pluripapillose. Leaves of secondary branches similar to those ofthe primary branches but smaller. Dioicous. Perichaetial leaves up to 5 mm long, cihate below, denticulate above. Setae 15-45 mm long, reddish, smooth; capsules 1.8-4 mm long, suberect and moderately curved to horizontal and arcuate, cylindric, asymmetric; operculum long-rostrate; cilia of endostome in 2s and 3s. Spores 12-24 µm, smooth.

  • Discussion

    Fig. 652

    T. delicatulum (Hedw.) B.S.G., Bryol. Eur. 5(fasc. 49/51). 1852.

    Hypnum delicatulum Hedw., Sp. Muse. 260. 1801.

    ?Thuidium schlumbergeri Schimp. ex Besch., Mem. Soc. Sci. Nat. Cherbourg 16: 236. 1872.

    T. erectumDuby, Mem. Soc. Phys. Geneve 24: 370. 1875.

    ?TamariscellaventrifoliaC. Müll., Bull. Herb. Boissier 5: 220. 1897.

    ?Thuidium ventrifolium(C. Müll.) Par., Index Bryol. 1294. 1898.

    ?T. subrobustum Card., Rev. Bryol. 37: 53. 1910

    Thuidium delicatulum var. delicatulum has stem leaves rather broadly acuminate and perichaetial leaves cihate at the margins. The var. radicans has stem leaves finely acuminate and ending in a slender point consisting of 2-8 hyaline cells in one row. The perichaetial leaves, though usuaUy characterized as eciliate, usually have a few short ciha and sometimes rather numerous well-developed ones. The var. radicans is wide-ranging, and its variability is such that determinations are often arbitrarily made. The var. peruvianum is rather more robust and has deeply phcate, finely acuminate stem leaves. It too is often difficult to separate from the variability of the var. delicatulum, but its more limited distribution is indicative of some value as a geographic segregate.

    In the American Southeast occasional specimens of T. delicatulum have leaf papillae more or less forked. In Mexico such expressions are common, with only a few papiUae forked or sometimes with most or all of them bifid or otherwise forked. It is difficult to separate the extreme form from an intergrading series, and it is not clear whether a name exists for such a form, although oneof the specimens originally cited as T. schlumbergeri C. Müll. (Orizaba, F. Mueller, MICH) is that form. In view ofthe considerable variability of T. delicatulum and the variability of this forked-papillose form, it seems best to include T. schlumbergeri in synonymy, at least provisionally.

    The legitimacy of the name Thuidium delicatulum has been called into question. Reasons why the name seems allowable are given in Crum (1984) and Crum and Anderson (1981).

  • Distribution

    On moist, shaded soil, humus, rock, logs, or stumps, less commonly on bark at the base of trees or even well up the trunks in particularly moist places, 1000-4200 m alt.; Chiapas, Chihuahua, Distrito Federal, Durango, Guerrero, Hidalgo, Mexico, Michoacan, Morelos, Nayarit, Oaxaca, Puebla, San Luis Potosf, Sinaloa, Sonora, Tabasco, Tamaulipas, Veracruz.—Mexico to northern South America; Newfoundland to Manitoba, south to Florida, Texas, and Arizona; Alaska, the Yukon, and British Columbia; Euro

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