Tortella humilis
Tortella rigens
tiny tornado moss, tortella moss
tortella moss
leaves densely foliose in rosulate habits, abruptly larger distally, the whorl-bases consisting of small leaves, loosely and variously incurled and contorted, occasionally somewhat crisped when dry, widespreading to patent when moist, typically oblong or oblong-spathulate, most leaves flat at mid leaf, somewhat concave and weakly keeled near the apex, not cucullate; 1.5–3.5(–4) mm;
base subclasping and often appearing narrower than the limb to somewhat broader and elliptic;
margins flat to weakly and broadly undulate, erect or broadly incurved near the apex;
apex typically obtuse to broadly or occasionally narrowly acute, usually stoutly mucronate;
costa short-excurrent, adaxial surface papillose, adaxial epidermal cells typically quadrate to short-rectangular and similar to the laminal cells throughout, sometimes smooth and narrowly elongate cells (8:1) toward the apex due to exposure of the stereid band or, in the extreme apex, exposure of the guide cells; in cross section adaxial epidermis present, often interrupted in the extreme distal portion of the leaf, proximal laminal cells yellow-hyaline, elongate, laxly thin-walled, gradually distally papillose, marginal basal cells longer and larger than median cells, occasionally approximating a band of differentiated cells;
proximal cells interior to the marginal gradually differentiated from the distal laminal cells;
distal laminal cells small, typically 6–7(–9) µm wide.
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.
about (0.5–)0.7–1.7 cm;
one per perichaetium, but often three to four per plant from different branches.
autoicous;
perigonia small, distinctive, stalked, flattened, usually single, rarely geminate, frequently yellow or orange, foliose buds of 2–6 leaves in axils of the distal leaves alongside and proximal to the perichaetium;
inner perichaetial leaves little differentiated from stem leaves.
apparently dioicous: only sterile and perichaetiate plants seen.
1.5–3 mm;
annulus deciduous in fragments;
operculum 1.2–1.5 mm;
peristome teeth, to over 1 mm, spirally wound 2 or 3 times.
asexual reproduction none.
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 humilis
Tortella rigens
Uniquely among species of the genus in the flora area, except for var. arctica of Tortella tortuosa, in T. humilis the proximal laminal cells of the leaf are typically gradually differentiated from the distal cells with a zone of cells intermediate in color, cell size, cell wall thickness and papillosity, the angle of hyaline marginal cell differentiation typically shallow across the leaf base, then extending up the margins in a U shape. This character is typical of the genus Trichostomum, with which Tortella is closely allied. Small (depauperate) plants of T. flavovirens may share this character. Typical basal cell differentiation in Tortella is abrupt, the angle of differentiated cells steep, the proximal echlorophyllose and distal chlorophyllose cell boundary sharp.
In cross section, the costa of Tortella humilis diminishes in size toward the leaf tip: sectioning distally along the leaf, the epidermal layer first disappears, leaving up to two stereid cells in width exposed. In some instances at the extreme apex, even the stereid layer disappears leaving the guide cells exposed. The well-developed peristome—elongate and conspicuously twisted—will distinguish Tortella humilis from specimens of T. flavovirens and Trichostomum species, whose peristomes are either not or little twisted, or are rudimentary. Any specimen without fruit is unlikely to be Tortella humilis. H. A. Crum and L. E. Anderson (1981) well described and illustrated the rare species Trichostomum spirale from the Great Lakes region (Ontario, Wisconsin, Minnesota) that, like Tortella humilis, is a nearly stemless plant with gradually differentiated proximal cells and a similar leaf shape. It also has stalked perigonial buds and is autoicous. It may be distinguished by the peristome teeth said to be short, erect and smooth or marked with spiral lines rather than spiculose papillae, the latter characteristic of peristomes of the genus Tortella.
(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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