Tortella fragilis
Tortella rigens
brittle crisp-moss, fragile tortella moss
tortella moss
leaves firm, coarse, rigid, uniform in size and shape along the stem and apex, lowermost leaves mostly without leaf tips, leaves typically fragile only at base of deciduous apical subula, stiffly erect-appressed, incurved (or stem-apical leaves somewhat twisted around the stem when dry);
erect and weakly spreading when moist, narrowly lanceolate to linear, narrowing gradually into the distal region until contracting into a narrower propaguloid region up to 1/2 the distal leaf length; broadly to narrowly concave, keeled toward the apex in nonpropaguloid leaves, 4–6 mm;
base broadly oblong;
margins plane to erect, not to somewhat undulate;
apex narrowly acute, those of nonmodified leaves shallowly channeled to subnaviculate, not cucullate, those of modified leaves long-subulate, fragile, the subula obtusely thickened and multi-stratose distally and often broken off, youngest leaves arising from the stem apex fully propagulose and subulate;
costa short-excurrent as a smooth or weakly denticulate mucro of 1–5 rhomboidal cells, in propaguloid leaves, internal cells in section appearing undifferentiated in the subula;
adaxial surface covered by quadrate to short-rectangular, papillose laminal cells throughout the leaf except in the propaguloid leaf portion where a narrow medial groove is covered by elongate (8:1) smooth cells;
cross section lunate and broad, adaxial epidermal cells may be interrupted in the center, exposing the adaxial stereid layer by about two cells in width, in propaguloid leaves stereid layers appear undifferentiated in the subula;
proximal laminal cells rather abruptly differentiated from distal cells, yellow-hyaline, elongate, firm to laxly thin-walled, smooth;
margin with a narrow line of firm- to thin-walled cells extending a short way up the lamina or to mid-leaf;
distal laminal cells frequently 2-stratose on one or both laminae beside the costa, or equally extending toward the margins in various degrees, and becoming completely 2-stratose and ultimately undifferentiated in the, deciduous leaf tips, rounded-quadrate or hexagonal, (9–)10–12(–13) µm wide, strongly papillose, areolation more or less distinct;
marginal cells in median leaf region undifferentiated, papillose-crenulate, along the distal median margin and into the subula differentiated as one or two rows of smooth, thick-walled, short-rectangular, (4–3:1), epapillose, yellowish cells leading into the subulate region and extending to the apex distinctly visible in at least some leaves, sometimes present only in young leaves on mature stems.
1–3 cm, rarely to 4 cm, densely foliose, leaf bases not evident between the leaves, central strand absent, tomentum rufous, dense, visible between the leaf bases especially along the lower stem.;
stem leaves firm, somewhat rigid, stiffly erect, especially proximal leaves, to loosely twisted and moderately contorted when dry, erect and somewhat spreading when moist, gradually larger and more crowded toward the stem tips, distal-most leaves usually more spreading than the erect leaves or leaf bases proximally;
leaf shape variable within clumps and on the same stem: short stems with leaves short, ovate-lanceolate, margins inwardly tapering to acute apices, longer stems with longer, more narrowly lanceolate leaves with more acuminate apices, the proximal leaves frequently narrowly lanceolate, distal leaves ovate or broadly ovate-lanceolate, generally narrowing gradually, but often some distal-most leaves with an abrupt narrowing with parallel sides in the distal quarter, leaf tips fragile, the older ones usually eroded; deeply concave to canaliculate-tubulose in longer leaves, 1.5–3(–4) mm;
base undifferentiated in shape to broadly ovate proximally narrowing gradually or abruptly to the lanceolate distal lamina;
margins variously plane, erect, to incurved, infrequently undulate in some leaves, apex fragile, acute to acuminate, abruptly ending before a sharp apiculus or narrowly acute and confluent with a conical, nearly mucronate apiculus; in shorter leaves naviculate to nearly cucullate, distinctly cucullate in the awl-shaped youngest leaves arising from the stem apex;
longer, narrow leaves with erect to broadly incurved margins extending to the leaf apex;
costa short-excurrent into a sharp, narrow, denticulate or smoothly conical mucro of 1–5(–10) cells, adaxial surface covered by quadrate, papillose laminal cells except for a narrow groove of elongate (8:1) smooth cells continuous throughout length of the leaf, in cross section, adaxial epidermal cells interrupted in the center, exposing the adaxial stereid layer by about two cells;
proximal laminal cells abruptly differentiated from distal cells, yellow-hyaline, elongate, 6–8:1, firm to laxly thin-walled, smooth;
marginal angle of differentiated cells steep due to the quadrate laminal cells extending juxtacostally far down into the proximal cell region, with a marginal row of firm to thin-walled, quadrate to short-rectangular smooth cells extending a short way up the lamina or to mid-leaf;
distal laminal cells frequently 2-stratose on one or both laminae juxtacostally or extending marginward as one to two pairs of cells, but never extending to the margins even in longer leaves with narrowed apices, rounded-quadrate or hexagonal, with slightly thickened walls, (12–)14(–17) µm wide, strongly papillose, areolation more or less distinct, differentiated distal marginal cells absent except in longer leaves possessing a somewhat differentiated and deciduous apex, these having obscure (due to erosion) to distinct thicker-walled, less papillose to smooth, elongate marginal cells.
1.5–2 cm, occasionally two per perichaetium.
dioicous;
perigonia not seen;
perichaetial leaves setaceous, fragile, with propaguloid modifications as in stem leaves.
apparently dioicous: only sterile and perichaetiate plants seen.
1.8–3 mm;
annulus none or of 1–2 rows of weakly vesiculose cells, operculum ca. 1.5 mm;
peristome teeth long, spirally wound, twisted 1–3 times.
asexual reproduction by deciduous, subulate, rigid, smooth-sided, distally thickened apices of all leaves.
asexual reproduction apparently by means of fragile leaf tips in the longer leaves.
terminal, leaves long-lanceolate, costa excurrent into a long awn or subula.
unknown.
Tortella fragilis
Tortella rigens
The long, subulate, rigid, usually fragile leaves with propaguloid tips that are not or only slightly contorted when dry are distinctive of Tortella fragilis. In ambiguous cases, the 2-stratose cross section of the distal leaves is diagnostic, but usually all that is necessary for identification is to demonstrate the smooth, elongate, thicker-walled cells along the leaf margin near the apex. The leaves may be stiff and merely arcuate in some plants, in others variously to strongly contorted-circinate, but not crisped. Such plants may be difficult to distinguish from Tortella tortuosa var. fragilifolia, which, however, has a fragile leaf lamina in addition to fragile leaf apices
Quadrate, papillose epidermal cells across the adaxial portion of the costa occur throughout the leaf of Tortella fragilis except in the proximal cell region and in the propaguloid-setaceous part of the leaf where the costa is often exposed in a continuous groove of elongate cells. This character is useful in distinguishing the species from T. rigens, which has a continuous band of smooth, elongate cells on the adaxial surface of the costa throughout the length of the leaf.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Tortella rigens is known in Europe from the alvars of the circum-Baltic states and central Europe. In North America, alvars appear confined to substrates of Ordovician and Silurian limestones and dolomites, being areas of exposed rock adjacent to bodies of water. The exposures occur around the Great Lakes and St. Lawrence River and associated lakes, such as Lake Simcoe in Ontario and Lake Champlain in New York and Vermont. The epithet refers to the somewhat rigid character of the leaves (but not as rigid as in T. fragilis). The proximal stem leaves when dry, however, may be as rigidly erect and straight as those of T. fragilis. Tortella rigens may have an adaxial epidermis in the proximal part of the leaf and the adaxial stereid layer is less exposed (usually by two stereid cells), hence there is a somewhat more narrow groove or channel running the length of the leaf. Tortella inclinata var. inclinata is regularly cucullate whereas T. rigens is distinctly cucullate usually only in the smallest leaves or on the smallest stems, or in the first whorl of leaves at the stem base. The leaf apices of T. inclinata var. inclinata may be acute to narrowly so, the distal laminal cells, however, are only 10–12 µm, while in section, the leaves are not 2-stratose juxtacostally, the leaves keeled beside the costa and broadly incurved distally. Tortella rigens has 2-stratose cells juxtacostally in the median portion of the leaf, and therefore the laminae spread out in a broadly concave leaf cross section, the distal cells 14 µm or more in width. Although T. rigens was not recorded as part of the Canadian flora by R. R. Ireland et al. (1987), it does appear in the most recent checklist of North American mosses (L. E. Anderson et al. 1990). The species has previously been reported from Colorado by W. A. Weber (1973), but several specimens collected and determined as that species can be assigned to other species, mainly T. alpicola and depauperate plants of T. fragilis. The cells sizes are undoubtedly large in T. rigens, to 14 or rarely 17 µm, but sizes to 14 µm correlated with reduced apical propagula can be demonstrated in T. fragilis.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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