Tortella humilis
Tortella tortuosa
tiny tornado moss, tortella moss
tortured 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.
leaves rather soft, uniform in size, strongly crisped or contorted with spirally curled tips when dry, flexuose- to widespreading when moist, long-lanceolate to linear-lanceolate, broadly to narrowly concave or nearly plane proximally to more or less keeled in the apical region, (2–)3–6.5(–7) mm;
base somewhat broader than limb, oblong;
margins usually shortly and strongly undulate, evenly crenulate-papillose, gradually subulate-acuminate, apex acumination confluent with the mucro, leaves at the extreme stem apex surmounted by a stout, multicellular mucro;
costa excurrent as a long, smooth or denticulate mucro or short awn, usually composed of 5–10 rhomboidal cells, adaxial cells of the costa variable, costa distal to the leaf base to the distal median region covered by an epidermis of quadrate to short-rectangular (2:1) papillose cells, in the distal adaxial region variously with a narrow or broader central groove of exposed, smooth, elongate (8:1) stereid cells, occasionally the groove conspicuous and extensive;
proximal laminal cells abruptly differentiated from distal cells, hyaline, laxly thin-walled;
distal laminal cells 1-stratose, quadrate, 7–10(–13) µm wide, marginal cells undifferentiated.
about (0.5–)0.7–1.7 cm;
one per perichaetium, but often three to four per plant from different branches.
0.9–2.7(–3.5) cm.
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.
dioicous, but seldom fruiting; perigoniate plants rare;
perigonia apparently few per stem, inner perigonial bracts ovate and abruptly apiculate, scarcely longer than the antheridia, 0.5 mm; perichaetiate plants common;
perichaetia numerous on the stem;
perichaetial leaves differentiated even in unfertilized perichaetia, slender and erect at the base, long, 5–5.5 mm, somewhat sheathing, distal part, consisting mostly of costa, setaceous-subulate, erect, in fertile plants, stiff and slightly flexuose, distinct and conspicuous above the tightly crisped cauline leaves when dry.
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.
1.5–3.3 mm;
annulus not vesiculose;
operculum 1.5–2 mm;
peristome teeth long and spirally wound 2 or 3 times, 1.1–1.4 mm.
asexual reproduction none.
asexual reproduction none except possibly through fragility of the lamina in some populations, or weakness toward the apex.
Tortella humilis
Tortella tortuosa
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.)
Varieties ca. 20 (3 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Plants red-green, appearing black proximally, densely foliose with a thick apical coma, leaf bases hidden; stems appearing atomentose but tomentum hidden in the bases of branch innovations; leaves not fragile, intact; leaves often strongly squarrose-recurved when wet, plane, not undulate; proximal laminal cells thick-walled and brownish, intergrading in shape and size with the distal cells, which are often nonpapillose in the area of merger; leaves broadly concave in section; costa at midleaf exposed adaxially by as much as four stereid cells | var. arctica |
1. Plants green or yellow-green, appearing brown proximally, loosely foliose, some leaf bases exposed, only slightly comose at stem apex; stems conspicuously tomentose; leaves fragile or not, erect- to erect-spreading when wet; undulate or plane; proximal laminal cells thin-walled and hyaline, sharply differentiated in shape and size from the papillose distal cells, which are papillose in the area of contact; leaves keeled in section, costa in apical region exposed adaxially by up to 2 stereid cells in width or completely covered with an adaxial epidermis of quadrate papillose cells | → 2 |
2. Leaves in tight, complex spirals when dry, appearing soft or lax throughout the stem length, not fragile or erose, leaf tips nearly all present; conspicuously undulate; leaf cross section without 2-stratose areas beside the costa, the lamina uniformly 1-stratose, lamina intact, the costa always differentiated into guide cells, stereids and epidermal cells, adaxial stereid layer never disappearing toward the apex, adaxial epidermal layer typically absent apically in a medial groove to two stereid cells in width. | var. tortuosa |
2. Leaves in loose, simple spirals or once circinate when dry, appearing firm or rigid, often fragile and erose, leaf tips often absent; inconspicuously undulate, especially when dry; leaf cross section with 2-stratose areas beside the costa, the lamina irregularly 2-stratose in patches, lamina tattered, costa occasionally appearing undifferentiated in apical region of the leaf, adaxial stereid layer occasionally disappearing toward the apex, epidermal layer may be continuous throughout the leaf length. | var. fragilifolia |
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