Monographs Details: Tortula fragilis T.Taylor
Authority: Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part One: Sphagnales to Bryales. Mem. New York Bot. Gard. 69 (1)
Description:Species Description - Plants variable in size, (5-) 10-25 mm high, in dense, lightto dark-brown tufts, or occasionally scattered among other mosses. Leaves crowded, longitudinally folded and spirally twisted around the stem (but httle crisped) when dry, wide-spreading when moist, 2-3.5 mm long, 0.75-1 mm wide, oblong-lingulate to spatulate, truncate to acute, brittle, with sheets of cells breaking off, sometimes along lines of weakness; margins revolute below (as much as 1/2 the leaf length) to plane, entire or crenulate; costa strong, yellow or red, finely to strongly papillose at back, abruptly tapered, percurrent or slightly excurrent as a mucro 1—3(—5) cells long; upper cells 9-15 µm, quadrate-hexagonal, with moderately thick walls, not particularly collenchymatous, bulging, with 3-8 papillae per cell; upper marginal cells not or weakly to strongly differentiated as a border of brownish, thicker-walled cells in about 2-3 rows; basal cells abruptly differentiated, becoming rather abruptly short-rectangular near the margins. Dioicous. Setae 10-15 mm long, red; capsules (1.5-)2-4 mm long, slightly curved, rather gradually tapered to the seta or with a distinct neck, red; operculum 1-1.5 mm long, red; peristomes 1-1.5 mm long, the upper divisions yellow, twisted about 1/2 turn, the basal membrane pale, about 1/4 the total length. Spores 13-20 µm, densely papillose. Calyptrae 3-3.5 mm long, brown.
T. fragilis Tayl., London J. Bot. 6: 333. 1847.
T. confusa Card., Rev. Bryol. 36: 87. 1909.
T. pringlei Card., Rev. Bryol. 36: 87. 1909.
T. chiapensis Broth, ex Card., Rev. Bryol. 36: 88.1909.
T. parva Card., Rev. Bryol. 36: 88. 1909.
T. parva var. latifolia Ther., Smithsonian Misc. Collect. 85(4): 22.
Tortula fragilis is widely distributed in Mexico except west of the Sierra Madre Occidental and in the Yucatan Peninsula. It shows considerable variability in size and leaf shape (apparently correlated with habitat conditions). Several populations from Mexico, Michoacan, and Oaxaca have leaf borders of thick-walled cells. Brood bodies have been reported. I have seen none, but detached leaf fragments do regenerate and probably serve as propagula. In some small, corticolous plants (Sharp 1588, Smith 2779, TENN), extreme fragmentation is evident, with an abnormal development of the lamina beyond the usual outline of the leaf (Fig. 253b). In such plants, several regions of each leaf seem to remain meristematic and produce scalloped or ruffled extensions eventually breaking off. In general, however, fragility of leaves should not be overemphasized as a diagnostic character. Some plants of T. fragilis have quite firm leaves, and the leaves of some other species, particularly when old, may become erose or broken.
Reports of Tortula glacialis (Kunze ex C. Müll.) Mont.
from the Pico de Orizaba (Veracruz) seem to be based on
misdetermined material of T. fragilis.
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