Tortula mucronifolia Schwägr.

Authority

Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part One: Sphagnales to Bryales. Mem. New York Bot. Gard. 69 (1): 1-452.

Family

Pottiaceae

Scientific Name

Tortula mucronifolia Schwägr.

Description

Species Description - Plants 2-5(-10) mm high, in yellowish- to bluish-green tufts. Leaves contorted and ± infolded and twisted when dry, loosely spreading when moist, 2.5-4 mm long and 0.75-1.5 mm wide, oblong to spatulate, acute to acuminate; margins revolute in the lower 1/2-3/4, entire; costa strong, yellow, smooth, excurrent into a smooth apiculus, short spine, or hair point; upper cells 14-24(-30) µm, irregularly rounded, hexagonal, quadrate, or rectangular, with firm walls somewhat thickened at the corners, smooth; marginal cells in the lower portion of the leaf long-rectangular in 1-2 rows, forming a weak border, those above similar in size to median cells (or slightly smaller) but thicker-walled in several rows, often forming a ± yellowish border; basal cells gradually differentiated. Autoicous. Setae 10-15 mm long, yellow or brown; capsules 2.5-4 mm long, slightly curved, with neck tapered to the seta, brown; operculum 1.5-2 mm long, brown; peristome about 1.5 mm long, the divisions red, strongly twisted in 1 or more turns, the basal membrane pale, 1/2-2/3 the total length. Spores 13-16 µm, finely papillose. Calyptrae about 3 mm long, yellow. [Description based on plants of the southwestern United States.]

Discussion

Fig. 242

T. mucronifolia Schwaegr., Sp. Muse. Suppl. 1(1): 136. 1811.

Features of note are the smooth, yellow costa ending in a smooth apiculus or short hair point, smooth cells, and revolute leaf margins weakly bordered at least below (and with upper marginal cells sometimes thicker-walled).

Some plants from the Pacific coast region of the United States are intermediate between this species and T. subulata Hedw., which is sporadic in occurrence in the mountains of the western United States and Canada (and to be expected in Mexico). The latter has leaves more strongly bordered by elongate cells and smaller, papillose upper median cells.

Two other species of the Pacific coast of the United States of some similarity to T. mucronifolia are T. amplexa (Lesq.) Steere and T. bolanderi (Lesq.) Howe. Both have leaves irregularly crisped w h e n dry, costa ending at or below the apex, or sometimes forming a mucro, and a border of isodiametric, thick-walled cells. Tortula amplexa has larger, less papillose leaf cells than T. bolanderi. A specimen of T. bolanderi from Baja California (Lightowlers & Davis 706, MEXU). was seen too late to be treated here.

Distribution

On soil over calcareous rock, among boulders or on cliff ledges; to be expected in Baja California.-Circumboreal and widespread across Canada and the western and northern United States. A specimen recorded from Guadalupe Island, Baja California (Moran 6731, SD, MICH), can be referred to T. californica.

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