Basionym: Barbula tortuosa var. angustifolia Jur., Laubm.-Fl. Oesterr.-Ung.: 123. 1882. ≡ Mollia tortuosa var. angustifolia (Jur.) Braithw., Brit. Moss Fl. 1: 253, 37Cg. 1887. ≡ Tortella tortuosa var. angustifolia (Jur.) Limpr., Laubm. Deutschl.1: 606. 1888. Type: [Austria]: ‘780. Barbula tortuosa β angustifolia, Tirol: Lienz, auf Kalkblöcken am Steige in die Kerschbaumeralpe, 5/8 1875, Gander’ (lectotype, designated here: W-2014-0004973!).

Note

Juratzka's understanding of his var. angustifolia was poorly conceived and the syntypes belong to more than one species. The chosen lectotype with well-developed, sporophyte-bearing cushion-sections seems to fit the protologue best. Barbula tortuosa var. longifolia Renauld may belong to the same species. It was described from the Pyrenees in the same year but in the last issue of Revue Bryologique 9 (Renauld 1882), whereas a handwritten remark on the cover page of HK´s personal copy of Juratzka (1882) gives 1 July 1882 as the date of purchase. Hence, var. longifolia would be, if the same, a later synonym. Tortella tortuosa var. setifera Velen. may be a further synonym. Unfortunately, both types could not be located.

Description

Plants medium-sized to large, in loose to dense cushions or turfs, light green (in shade), yellowish or brown (in full sun), interior of cushions pale greyish brown. Shoots erect, up to 8 cm long, densely or loosely and evenly foliated, irregularly branched. Narrow-leaved branch innovations with restricted growth absent. Stems red-brown when mature, in transverse-section circular to triangular, up to 350 µm wide, hyalodermis distinct, cortex red-brown, of 1–3 rows of distinctly thick-walled cells, cylinder cells thin- to thick-walled and rather large, central strand absent. Leaves 3.0–12.0 × 0.3–1.0 mm, linear-lanceolate to linear, length-width ratio 8–15:1, when dry contorted around stem (xeromorphic extremes) or loosely to strongly curled, uppermost part straight for some distance, when moist erecto-patent to spreading, almost straight to moderately secund in top view, quite fragile, mainly cross-breaking. Limb gradually and very narrowly acuminate, distally canaliculate or ± keeled (in shade). Sheath longly or shortly rectangular to ovate, not or moderately widened, non-coloured to yellowish. Apex ending in a narrow and sharp, yellowish mucro, 200–400 µm long. Costa strong, in shade-morphs in upper part dorsally with spines, in mid-leaf with mixed papillae and spines, at limb-sheath transition 70–200 µm wide, gradually narrowed to apex, occupying about a quarter to a sixth of leaf width in mid-leaf, in transverse-section at leaf base ± 2–3 times wider than long, in mid-leaf semicircular to rounded triangular and about 2 times wider than long, isodiametric in apical part, adaxial epidermis mostly continuously absent (more rarely present), abaxial epidermis absent, guide cells usually in a single row. Margins flat, crenulate by papillosity. Lamina hardly to distinctly undulate (mainly in mid-leaf), unistratose, transition zone between limb and sheath V-shaped, transition rather abrupt. Marginal cells in mid-limb mostly wider than long or irregular in shape, often less papillose than laminal cells. Mid-limb cells ± isodiametric, 5–12 µm wide, thin-walled and flat (in shade) to thick-walled and bulging (in sun), with densely set, in shade fine, stellate, conic or bacillar papillae, in sun thick and flattened papillae (in lower limb often forming rings in periphery of cells), papillosity in younger leaves obscuring areolation. Inner papillose transition cells sometimes with thickened cross-walls. Sheath cells in upper part mostly shortly rectangular and thick-walled, often forming a yellowish zone. Lower, inner ones 30–120 × 5–10 µm, thin- to moderately thick-walled. Male plants smaller, occasionally observed. Sporophytes occasionally to frequently present. Seta reddish in basal half, yellowish in upper half, rather thin, 15–30 mm long, urns straight to moderately curved, 2.0–3.5 mm long.

Although molecularly distinct, among some of the species of the complex Tortella angustifolia appears intermediate in a few taxonomically important characters. The dorsal costa has usually both spines and papillae in shade morphs, the ventral surface is much more frequently free of isodiametric, papillose cells than in habitually similar taxa within the complex. Xeromorphic expressions often have lower limb cells with rings of thick and flattened papillae in the periphery of the cells, leaving the cell middle seemingly without papillae. On the other hand, scio- and hygromorphic plants have a dense and rather fine leaf papillosity. A good field character of T. angustifolia is the straight uppermost portions of dry leaves, oriented at right angles to the stem axis, which is most distinct in relatively xeromorphic plants. The leaves of T. angustifolia often reach 10 mm in length and occasionally even 12 mm; hence, it develops the longest leaves among the Pottiaceae. With T. tortuosa s. str. it shares the absence of the stem central strand but has densely papillose leaf cells like in the group of narrow-leaved taxa (T. bambergeri, T. dolomitica, T. robusta) which have a central strand.

Ecology and distribution

Tortella angustifolia is a competitive species, preferring moderately shaded rock habitats predominantly of northern exposure but at higher elevations it tolerates full sun. It shows a rather wide amplitude with respect to pH, occurring under subneutral to basic conditions; it can thus also grow on base-rich siliceous rocks. Besides rock, it invades, sometimes even dominantly, dolomitic gravel and sand. It is almost absent from manmade habitats, seemingly avoiding sites rich in nutrients. In shaded limestone habitats of the montane belt of the Alps it is often the only Tortella, but otherwise mixed stands with nearly every other Tortella species are occasionally found. Europe-wide, it seems to occur mainly in mountainous regions. In the Alps, it is a widespread and often frequent element from the low montane to the subnival belt, reaching about 2700 m a.s.l. In Sweden, it is much rarer and mainly confined to the southern part. We saw some material from Scotland and the Balkan Peninsula.

Basionym: Trichostomum fleischeri E. Bauer, Musci Europaei Exsiccati 15: n. 741. 1910. ≡ Tortella tortuosa var. fleischeri (E.Bauer) Latzel, Hedwigia 66: 138. 1926. Type: [Austria]: „741. Trichostomum fleischeri Bauer n. sp. ster., Steiermark: Alt-Aussee, am Moosberge auf feuchten Alpenwiesen feste, teppichartige Polster bildend, 900 m s. m, 19 Sept. 1908 legit M. Fleischer, E. Bauer, Musci exsiccati' (lectotype, designated here: GZU!, isolectotypes in S, reg. no. B218490! and B218491!).

Tortella kmetiana Pilous, Rozpravy Čzechoslovenské Academie Vĕd a Umeĕní 71(2): 22. 1. 1961.

Note

Tortella kmetiana was described by Pilous (1961) from ‘terra graminosa calcarea pr. Bešeňová, ca. 530 m’ in northern Slovakia. From PR we received only a specimen that was collected by the author in ‘7. 1960’, whereas the original description gives ‘17. 7. 1958’. It may be the holotype, if a simple date confusion occurred, or a topotype, if Pilous really revisited the site two years later. Nevertheless, when compared with the protologue and Pilous’ drawings, this material certainly represents the same species. According to a revision label, it was studied by R. Düll in 1994, suggesting that it is the only extant specimen.

Description

Plants small to large, in dense but when removed easily disintegrating, often wide turfs or cushions, light green, yellowish or ferrugineous, interior mostly rusty brown to almost blackish. Shoots erect, up to 7 cm long, densely foliated, often with many narrow-leaved branch innovations with restricted growth (but mostly absent in small-leaved plants). Stems redbrown when mature, in transverse-section circular to triangular, up to 350 µm wide, hyalodermis and cortex distinct, cylinder cells redbrown to red (rarely yellowish-brown) and usually thick-walled, central strand mostly strong, up to 60 µm wide. Leaves 2.0–6.0 × 0.5–1.0 mm, lanceolate to linear-lanceolate, length-width ratio 4–7:1, when dry ± erect and contorted around axis or incurved and contorted (rarely strongly curled), when moist patent to recurved, not to strongly secund (or sigmoid) in top view, not to moderately fragile. Limb narrowly triangular, gradually acuminate, keeled. Sheath ± quadrate, mostly distinctly widened, non-coloured to yellowish. Apex ending in an often strongly toothed, sharp, yellowish to brown mucro, 70–200 µm long. Costa in shade-morphs dorsally with strong spines, papillae absent, at limb-sheath transition 60–140 µm wide, gradually narrowed to apex, occupying about an eighth to a sixth of leaf width in mid-leaf, in transverse-section at leaf base ± 1.5–2 times wider than long, in mid-leaf semi-circular and about 1.5 times wider than long, isodiametric in apical part, adaxial epidermis nearly always absent along a narrow mid-line (very rarely present), abaxial epidermis absent, guide cells usually in a single row. Margins flat, often crenulate by bulging cells. Lamina not to strongly undulate, unistratose, transition zone between limb and sheath broadly V-shaped and rather abrupt to U-shaped or W-shaped and gradual. Marginal cells in mid-leaf mostly isodiametric, often less papillose. Mid-leaf cells ± quadrate, 8–12 µm wide, mostly thick-walled, with 2–5, fine and simple (in shaded, moist sites) to coarse and forked papillae; papillosity in younger leaves not obscuring areolation. Juxtacostal transition cells in older leaves frequently with distinctly thickened cross-walls. Sheath cells with a marked discontinuity between inner and outer cells, thin- to thick-walled, shortly to longly rectangular, lower, inner ones 20–100 × 8–12 µm. Male plants unknown. Sporophytes very rare (probably only hybridogenous with largely aborted spores).

The Alpine T. fleischeri resembles T. squarrosa in habit and leaf shape and has even a marked discontinuity between the outer and inner sheath cells, although the latter are only narrower and not deviating in colour or length. The similarity is mainly due to their occurrence in similar vegetation types, T. squarrosa in xerothermic grassland and T. fleischeri in grassland above the treeline. The densely set and partly patent older leaves of T. fleischeri and the usually many branch innovations form a thick mantle around the stems, which makes this species a successful competitor against vascular plants, and this is also the reason why collections commonly disintegrate. In both plastid and nuclear markers, T. fleischeri appears closely related to T. tortuosa s. str. with which it shares the ferruginous colouration, keeled leaves, the thickened cross-walls in the leaf transition cells and the absence of papillae from the dorsal costa surface. However, T. fleischeri is easily distinguished from T. tortuosa by its constantly present central strand in the stem. Tortella fleischeri is most easily confused with the seemingly only remotely related T. commutata. From the latter, it differs in, e. g., its ferruginous (versus brown) secondary colouration, an evenly grading, triangular limb and a distinctly widened sheath which is hardly longer than wide, the mid-line of adaxial costal surface almost always with exposed stereids throughout and a usually thicker stem central strand surrounded by thick-walled and often red cylinder cells. Sporophytes were found only a few times in T. fleischeri. When spores were present, they appeared aborted. Hence, these sporophytes are likely of hybrid origin and male plants, which were never observed, may not exist.

Ecology and distribution

Tortella fleischeri is a strict calcicole which was originally described from wet meadows where it was found in large carpet-like stands. The synonymous T. kmetiana also originates from a calcareous meadow (over travertine). It is a competitive moss of alpine grassland and cushion-plant communities. Most frequently, however, the species occurs on ± humid and mostly N-facing calcareous rocks, where its stands are often more cushion-like. The most important associate of the complex is T. robusta, followed by T. angustifolia. In exposed sites, it sometimes grows together with T. commutata and T. splendida. Its third habitat type is gravel fields in the mountains or along natural rivers, where it, often only ephemeral, reaches rather low elevations (about 500 m a.s.l. or less). Low elevation occurrences are also known from dolomitic gorges. Nevertheless, this cryophilous moss prefers sites at or above the treeline. In the upper alpine and subnival belt of the calcareous mountain ranges, it proved to be the most common Tortella species. The hitherto highest known locality in the eastern Alps is at 2790 m a.s.l. (Schlüsslmayr 2019; as T. tortuosa var. fleischeri). Despite its frequency in the Alps, we have otherwise only seen collections from Slovakia (type of T. kmetiana), Montenegro (Durmitor Mts of the Dinarides) and, surprisingly, also Scotland. It is absent from northern Europe and the Arctic where it is ecologically replaced by the habitually similar T. × cuspidatissima and T. spitsbergensis.

Basionym: Barbula tortuosa var. robusta Pfeff., Neue Denkschriften der Allgemeinen Schweizerischen Gesellschaft für die Gesammten Naturwissenschaften 24(5): 37. 1869. Type: [Switzerland]: ‘Barbula tortuosa robusta Pfeffer, Sayiserköpfe 2000 m, 21/5 68, Pfeffer’, (lectotype, designated here: CHUR s.n.!, isolectotype in S, reg. no. B220011!). The type material represents a coarse shade morph, grown between limestone boulders.

Description

Plants medium-sized to large, in moderately dense turfs or cushions, pale greyish green to pale yellowish, at most light brown (in full sun), interior pale greyish brown. Shoots erect, up to 5 cm long, densely or loosely and evenly foliated, irregularly branched. Narrow-leaved branch innovations with restricted growth absent. Stems brown when mature, in transverse-section circular, up to 350 µm wide, hyalodermis and cortex distinct, cylinder cells yellow-brown, redbrown or brown, thick- or thin-walled, central strand mostly thin but up to 50 (–70) µm wide, usually occupying less than a fifth of stem diameter. Leaves 3.0–10.0 × 0.3–1.0 mm, linear-lanceolate to linear, length-width ratio 7–12:1, when dry incurved and inrolled or upper part contorted, when moist patent (rarely spreading to recurved), straight to moderately secund (or sigmoid) in top view, moderately to distinctly fragile, cross-breaking. Limb gradually and very narrowly acuminate (sometimes parallel-margined in mid-third and acuminate only in upper third), distally canaliculate or ± keeled (in deeper shade). Sheath rectangular to ovate, not or distinctly widened, mostly yellowish (more rarely non-coloured). Apex ending in a toothed, short and narrow to long and hardly toothed, yellowish to brown mucro, 70–200 µm long. Costa strong, in upper part with indistinct spines, in mid-leaf on dorsal surface usually papillose with mostly densely set, simple or rarely forked papillae, at limb-sheath transition 70–200 µm wide, gradually narrowed to apex, occupying about a third to a fifth of leaf width in mid-leaf, in transverse-section at leaf base ± 2 times wider than long, in mid-leaf semi-circular and about 1.5 times wider than long, isodiametric in apical part, adaxial epidermis present for much of its length (rarely absent), abaxial epidermis absent, guide cells usually in a single row. Margins flat or somewhat incurved, crenulate by projecting cells. Lamina not to weakly undulate (mainly in mid-leaf), unistratose (to bistratose at transition to costa), transition zone between limb and sheath usually narrowly V-shaped and abrupt. Marginal cells in mid-limb usually wider than long (if marginal row of elongated sheath cells not extenting so far), often less papillose than laminal cells. Mid-limb cells ± isodiametric, 6–10 µm wide, usually thick-walled and often bulging, with densely set and regular to irregular knobbly (in deeper shade sometimes c-shaped or forked) papillae, papillosity in younger leaves obscuring areolation. Transition cells occasionally with more thickened cross-walls. Sheath cells thick- to thin-walled, shortly to longly rectangular, lower, inner ones 40–140 × 8–16 µm. Male plants smaller, rare. Sporophytes rarely present. Seta red in basal two thirds, yellowish in upper third, rather thin, 20–30 mm long, urns straight, 2–3 mm long.

According to the plastid markers, T. robusta is closely related to T. tortuosa s. str., whereas the affinities according to ITS are more obscure. Morphologically, it combines characters found in T. dolomitica on the one hand and T. tortuosa on the other. Characteristic features are the narrow and nearly straight, patent leaves when moist, the canaliculate (in deeper shade more keeled) limb, the dense papillosity of the leaf lamina, the usually papillose dorsal costa surface, and the presence of a stem central strand. The development of the latter is highly variable, commonly absent in stem cross-sections narrower than 200 µm, thin in stems less than 300 µm but up to 50 or even 70 µm wide in stems reaching 350 µm. By far the best field characters are the light greyish green to pale yellowish colouration and the distinctly incurved-inrolled leaves of dry plants in top view. The epithet (based on type material) suggests a coarse plant, but the size is actually highly variable.

Ecology and distribution

Tortella robusta is often the only species of the complex in calcareous late snow areas. Expressions in this habitat are, however, often quite small-leaved. More vigorous cushions with larger leaves occur on N-facing, shaded and humid rocks and in adjacent moist meadows. Occurrences in S-exposure are rare. It is a rather strict calcicole, only rarely tolerating base-rich siliceous rock. When sufficiently moist, it invades also calcareous gravel and sand. The most frequent associate of the complex is T. fleischeri, more rarely it grows together with T. angustifolia and T. commutata. Although mainly a high-elevation species, ascending to about 2500 m a.s.l., it occasionally pops up in low quantity (and probably ephemeral) at lower altitudes, particularly in road-cuttings. The species has a characteristic Arctic-alpine distribution area. It is widespread in the Alps and, additionally, we have seen some material from Montenegro and Scotland. We expect that it occurs also in other high mountain ranges like the Carpathians and the Pyrenees. In northern Europe, it mainly occurs in the Scandes, rarely in northeastern Finland.

Diagnosis: Differing from T. tortuosa s. str. in a rudimentary tomentum, usually straight leaves when moist (in top view), an ovate leaf base, a canaliculate to tubulose limb, costal transverse sections usually with two rows of guide cells and being biconvex in lower leaf, a non-undulate lamina, densely papillose laminal cells, a mostly rather gradual limb-sheath-transition and yellowish sheath cells.

Type: Austria, Steiermark, Hochschwab Mts., Trenchtling, S of Hochturm, 1950 msm; S-facing dolomite outcrops in Carex firma-meadow, 26 Oct. 2013, leg. H. Köckinger no. 15036 (holotype: S, reg. no. B248499!, isotype in GZU!).

Note

The holotype of Mollia tortuosa var. arctica Arnell at UPS (!) (‘In valle flum. Lena, Kumachsur, 70° 30´ lat. Bor. Ad rivulum in monte calcaria, 31 July 1898, H. Nilsson-Ehle’), as well as the isotype at S, have a distinct stem central strand and a leaf morphology identical to the plants which were treated as Tortella ×cuspidatissima in Werner et al. (2014). A further isotype at LE seems to be similar since it was reported as Trichostomum cuspidatissimum Cardot & Thér. by Savicz-Ljubitzkaja (1961). This report was doubted by Crundwell and Nyholm (1963), but it confirms that obviously all type-material belongs to the same plant, except for the intermixed Didymodon giganteus (Funck) Jur. We could not find a hint of the presence of a second Tortella element. Possibly, the two authors were so convinced that nothing closely related to T. tortuosa can have a stem central strand that they even did not check the type material for this character or, alternatively, a too thin stem was cut. The holotype is not available for loan and was therefore not checked by Eckel (1998) or Werner et al. (2014). As a consequence, the plant called Tortella arctica or T. tortuosa var. arctica by Crundwell and Nyholm (1963) and more recent treatments does not have a name. For the time being, the closely related T. splendida, here described from plants of the Alps, includes also the non-European Arctic plants of T. arctica auct., but the relationship of these two elements requires more careful study.

Description

Plants medium-sized to large, in dense turfs or cushions, light green to yellowish-brown, chestnut-brown or ferrugineous to rusty brown, interior pale greyish brown to dark and sometimes rusty brown. Shoots erect, up to 6 cm long, densely and evenly foliated, irregularly branched. Narrow-leaved branch innovations with restricted growth often present. Stems redbrown when mature, in transverse-section circular, up to 350 µm wide, hyalodermis distinct, cortex distinct and up to 5 rows wide, cylinder cells yellow-brown to redbrown, thin- to thick-walled, central strand absent. Leaves 3.0–7.0 × 0.6–1.2 mm, lanceolate to linear-lanceolate, length-width ratio 5–7:1, when dry patent in mid-leaf and erect to incurved and ± contorted in upper part, when moist patent to spreading, straight to weakly secund (or flexuose) in top view, non-fragile or only apices breaking off. Limb gradually and narrowly acuminate, distally canaliculate to tubulose (rarely ± keeled in shade). Sheath shortly ovate, distinctly widened, mostly yellowish (more rarely non-coloured). Apex ending in a weakly toothed, sharp, yellowish to brown mucro, 100–300 µm long. Costa moderately strong, glossy, dorsally usually smooth (rarely with indistinct spines), non-papillose, at limb-sheath transition 60–150 µm wide, gradually narrowed to apex, occupying about a quarter to a sixth of leaf width in mid-leaf, in transverse-section at leaf base ± 2–3 times wider than long, in mid-leaf about 1.5–2 times wider than long, isodiametric in apical part, in lower half biconvex (rarely semi-circular); adaxial epidermis present for much of its length, except for apical part, abaxial epidermis absent, guide cells usually in two layers (rarely a single one) or rows (in section). Margins flat, crenulate by projecting cells to smooth. Lamina not undulate (rarely weakly in mid-leaf), unistratose (very rarely bistratose spots in upper part), transition zone between limb and sheath V-shaped (often stepped) and rather abrupt to more frequently U-(sometimes W-)shaped and very gradual. Marginal cells in mid-limb isodiametric to elongate, weakly papillose or smooth. Mid-limb cells ± isodiametric, 5–10 µm wide, mostly thick-walled but hardly bulging, with densely set and regular to irregular knobbly (in shade rarely almost c-shaped) papillae. Transition cells never with more thickened cross-walls. Sheath cells thick- to thin-walled, shortly to longly rectangular, lower, inner ones 20–100 × 8–20 µm. Male plants not known. Sporophytes not known.

Both nuclear and plastid DNA data show a close relationship of T. splendida (including T. arctica auct.) to T. fragilis. They share the absence of a stem central strand, non-secund and non-undulate leaves, a canaliculate to tubulose limb, a similar areolation, dense cell papillosity and an at least occasional presence of small bistratose spots in uppermost lamina in T. splendida (and T. arctica auct.) compared with the more constantly bistratose upper lamina in T. fragilis. However, because of the highly modified propaguloid leaf apices in the latter the differentiation is normally easy. In rare shade-morphs of T. fragilis they may be nearly absent, but such plants have a different leaf shape (Eckel 1998).

In exposed habitats, this species is always coarser and prettier than associated species of the complex, which induced us to call it T. splendida. When well developed, large morphs are characterised by densely set and non-fragile, almost tubulose leaves, usual absence of a tomentum, a biconvex costa with two layers (two rows in transverse section) of guide cells in the lower leaf and finely papillose, small lamina cells. At the harshest sites, the costae become ± flat adaxially and the guide cells may lose their second layer, the laminal cells become larger, more thick- and brown-walled, and the papillae coarser and the limb-sheath transition more gradual and more U-shaped. In addition, the sheath cells tend to be shorter, more thick-walled, and more strongly yellowish. Such plants are morphologically very close to Arctic collections.

Eckel (1998) treated T. arctica auct. at varietal rank within her wide concept of T. tortuosa because of difficulties in distinguishing collections from American non-Arctic occurrences. It is true that Alpine plants from somewhat protected sites or from shaded cushion margins may also have a few leaves that are slightly secund and have a few undulations, but all other characters remain stable. Eckel´s concept allows the occasional presence of a thin central strand in the stem, seemingly including, beside T. arctica auct., also the hybridogeneous T. ×cuspidatissima, respectively T. arctica sensu type.

The recently described, thermophilous T. mediterranea (Köckinger et al. 2018) is strikingly similar in habit and in part of the microscopic features but differs in a rather dull colouration, a pronounced leaf fragility, wider cells of the inner mid-sheath (despite a narrower base), an always single layer of costal guide cells and usually more numerous ventral than dorsal stereid layers.

Ecology and distribution

Tortella splendida is a distinctly cryophilous species, in the Alps only found above the treeline. However, it avoids habitats with a long-lasting snow cover. It therefore occurs on steep, S-facing rocky slopes and only rarely in N-exposure and then where strong winds prevent a thick snow layer. At its lower sites it invades rock (in particular dolomite, rarely limestone and base-rich siliceous rock), whereas at the upper limit it develops turfs in meadows, usually belonging to the plant community Caricetum firmae. Mixed stands are known with T. fleischeri, T. commutata, and, at dolomitic sites, T. densa. The species is scattered to rather widespread, but normally in low quantity, in the mountain ranges of the eastern Alps of Austria between 1700 and 2500 m a.s.l. We also saw two collections from Switzerland whereas it is obviously absent from northern Europe. The included T. arctica auct. is known from Arctic and northern Central Asia, Arctic North America, and the Rocky Mountains.

Basionym: Tortula tortuosa Hedw., Species Muscorum Frondosorum 124: 1801. Type: ‘Hedwig s. n.’, top row of specimens on sheet [lectotype (Ellis and Price 2013): G, reg. no. G00040331!].

Tortella spinidens (G.Roth ex Zodda) Levier & G.Roth, Hedwigia 49: 219. 7 f. 3. 1910. ≡ Tortella tortuosa var. spinidens G.Roth ex Zodda, Malpighia 21: 488. 1907. Type: [Italy]: ‘Tortella spinidens Lev. & Roth., n. sp. (earlier naming T. fragilis var. dentata crossed out), Campello-Monti (prov. Novar. Pedemontii), in ascensu ad alpem Foscalina, juxta semitam, 1400 m, 27. Jul. 1904, leg. E. L., E. Levier - Bryotheca Italica, no. 163’ (lectotype, designated here: herb. G. Roth in S, reg. no. B233655!).

Tortella undulatifolia Dixon, 150th Anniversary Volume, Royal Botanic Garden Calcutta 180. 1942. Type: ‘India. Kashmir, Lidar and Sind Valleys, 2200-4200m’, Garrett & Lillie 2453 (holotype: BM-001006420-Dixon!).

Notes

Description

Plants medium-sized to large, in rather loose cushions or turfs, green to ferrugineous, interior of cushions pale greyish to dark brown, rarely blackish. Shoots erect, up to 5 cm long, rather loosely foliated, irregularly branched. Narrow-leaved branch innovations with restricted growth absent. Stems redbrown when mature, in transverse-section circular to triangular, up to 350 µm wide, hyalodermis and cortex distinct, cylinder cells redbrown to red and ± thick-walled, central strand absent. Leaves 4.0–10.0 × 0.3–0.7 mm, linear-lanceolate to linear, length-width ratio 8–15:1, when dry in basal half erect to patent and distally incurved and strongly contorted around axis (like a corkscrew) or generally strongly curled, when moist patent to recurved, weakly to strongly secund or sigmoid in top view, not to strongly fragile. Limb gradually acuminate or parallel-margined in mid-leaf and only in upper third acuminate, keeled. Sheath shorly to longly rectangular, not or weakly widened, usually non-coloured (rarely yellowish). Apex ending in a toothed, sharp, yellowish mucro, 100–300 µm long. Costa in shade-morphs dorsally with distinct spines, in sun smooth, never papillose, at limb-sheath transition 50–150 µm wide, gradually narrowed to apex, occupying about an eighth to a fifth of leaf width in mid-leaf, in transverse-section at leaf base ± 1.5–2 times wider than long, in mid-leaf semi-circular and about 1.5 times wider than long, isodiametric in apical part, adaxial epidermis present at least in mid-leaf, abaxial epidermis absent, guide cells usually in a single row (sometimes a single cell indicating a second row). Margins flat, crenulate by projecting cells and papillae. Lamina weakly to strongly undulate, unistratose, transition zone between limb and sheath narrowly to broadly V-shaped and rather abrupt, rarely U-shaped and more gradual (in xeromorphic plants). Marginal cells in mid-leaf ± isodiametric. Mid-leaf cells ± quadrate, 8–14 µm wide, thin- to thick-walled, with spaced, fine and bacillariform (in shaded, moist sites) to coarse and forked (rarely ± c-shaped) papillae (in sun), usually rather evenly distributed over lamina; papillosity in younger leaves not obscuring areolation. Juxtacostal transition cells frequently with distinctly thickened cross-walls, often reaching far into limb (best seen in older leaves). Sheath cells mostly thin-walled, shortly to longly rectangular, lower, inner ones 40–120 × 8–16 µm. Male plants smaller, occasionally seen. Sporophytes occasionally present. Seta reddish in basal half, yellowish in upper half, 20–30 mm long, urns straight to weakly curved, 3–4 mm long.

In lowland areas of Europe, T. commutata and T. tortuosa s. str. are often the only representatives of the complex that share the keeled limb, an often strong leaf undulation, a narrow costa in comparison with the leaf width, and often markedly thickened cross-walls in the limb-sheath transition zone, best seen in older leaves. In the field, they can be distinguished by their differing length-width ratios of the leaves (about 4–8:1 versus 8–15:1) and the less strongly versus more strongly curled leaves in the dry state. In the sun, T. commutata has a brown colouration whereas T. tortuosa is usually ferruginous. Microscopically, the former has the general ability to develop a stem central strand whereas the latter does not have it. There are, however, problematic large-celled forms of T. commutata (in particular its semi-cryptic var. valida) which express a central strand only when stems are very thick (300 µm and more in diameter). Such plants usually have groups of ± c-shaped laminal papillae over the laminal cells; such papillae only rarely occur in T. tortuosa, where they are mostly bacillariform, knobbly or forked and rather regularly distributed over the lamina. When fruiting, sporophytes are somewhat larger in T. tortuosa.

Ecology and distribution

Tortula tortuosa in the strict sense is the least calciphilous species of the complex. The pH-values of its substrates range from approximately 5.5 to 7.0, thus from moderately acid to neutral. In fact, it prefers base-rich siliceous rock where it grows in crevices, niches and on exposed surfaces, both in full sun and shade. When it occurs on calcareous rock, it prefers boulders, stones and similar rock habitats exposed to rain, but avoids strongly basic conditions, in particular moist rock niches and crevices. It can also grow on artificial walls, often made of concrete, and on roofs. In calcareous areas it may be found as an epiphyte, sometimes on stony soil, base-rich humus and above the treeline as a frequent part of alpine to subnival cushion plant stands or grassland over base-rich (sometimes base-poor) siliceous rock. It occurs up to almost 3000 m a.s.l. Mixed stands are often met with T. commutata, T. angustifolia, and T. fragilis but only rarely with other Tortella-species. It is the most frequent species of the complex in Northern, Western, and the lowlands and lower mountain ranges of central Europe, whereas in many limestone areas of the Alps and southern Europe it is not the dominant member of the T. tortuosa complex.