Published In:
Die Laubmoose Deutschlands, Oesterreichs und der Schweiz 1: 599. 1888. ( Laubm. Deutschl.)  
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(Last Modified On 11/7/2011)
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Acceptance
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Accepted
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(Last Modified On 11/7/2011)
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Nomenclature:
15. TORTELLA Plates 18– 19. Tortella (Lindb.) Limpr., Laubm. Deutschl. 1: 599, 1888, nom. cons. Lectotype: Tortella caespitosa (Schwaegr.) Limpr. Mollia subg. Tortella Lindb., Musci Scand. 21, 1879. Tortella subg. Tortella Limpr., Laubm. Deutschl. 1: 600, 1888, nom. illeg. Barbula subg. Tortella (Lindb.) Kindb., Eur. N. Amer. Bryin. 2: 245, 1897. Tortella subg. Eutortella Roth, Eur. Laubm. 1: 344, 1903, nom. illeg. Trichostomum subg. Tortelloidea Roth, Eur. Laubm. 1: 315, 1903. Tortula sect. Tortuosae De Not., Mem. R. Acc. Sc. Torino 40: 288, 1838. Type: Tortula tortuosa Hedw. Tortula sect. Caespitosae De Not., Mem. R. Acc. Sc. Torino 40: 287, 1838. Type: Tortula caespitosa Schwaegr. Barbula sect. Tortuosae BSG, Bryol. Eur. 2: 86, 1842 (fasc. 13–15 Mon. 24). Type: Barbula tortuosa (Hedw.) Web. & Mohr. Barbula sect. Tortella C. Müll., Syn. 1: 599, 1849, nom. illeg. incl. sect. prior. Barbula sect. Fragiles Schimp., Syn. 181, 1860. Type: Barbula fragilis (Hook. & Wils.) BSG. Tortula sect. Fragiles (Schimp.) Lindb., Oefv. K. Svensk. Vet. Ak. Foerh. 21: 214, 1864. Type: Tortella fragilis (Hook. & Wils.) C. Hartm. Mollia sect. Tortella (Lindb.) Braithw., Brit. Moss Fl. 1: 230, 247, 1885.
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Habitat:
Found on soil, rock or organic substrates on all continents.
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Notes:
Tortella and Trichostomum (including subg. Oxystegus) are distinguished at present by characters that are somewhat variable. A thorough reevaluation is needed through revision of both genera together. Tortella simplex, for instance, has much the appearance of Trichostomum brachydontium, especially in the characteristic weakly reflexed apex ending in a stout mucro, and its basal cells are only weakly differentiated as a vee; this species may be more closely related to Trichostomum than to Tortella in spite of its somewhat twisted peristome. The vee-shaped area of basal cells is generally easily distinguished in most species of Tortella, yet, in some, the differentiated basal cells do not rise very high along the margins (Pl. 18, f. 6, forming a rather low vee) or they are not sharply different in size and shape or thickness of cell walls from the upper laminal cells. Some species with a vee-shaped basal cell region (e.g. Tortella flavovirens) have untwisted, often short peristomes, similar to those of Trichostomum s. lat. Two autoicous species, Tortella lilliputanum (Pl. 19, f. 1–3) and T. fruchartii, have cleistocarpous capsules and a distinctly vee-shaped basal laminal cell area, plus a stem section with a characteristic well developed tortellaceous hyalodermis. The gametophytes are clearly Tortella; the two taxa are much alike and may be conspecific. Species of Tortella with reduced sporophytes (T. eckendorffii lacks a peristome) are presently few, but more should be added to Tortella when Hyophila and other eperistomate genera are revised, e.g. Tortella walkeri is eperistomate and stegocarpous. Pseudosymblepharis is usually distinguishable by the narrow upper laminae and sharply broadened and sheathing leaf bases, but specimens of Tortella tortuosa with cirrhate leaves have much the appearance of Pseudosymblepharis. Some species of Pseudosymblepharis, also, are much like Tortella in the broad upper laminae. Trichostomum hibernicus has these characters of Pseudosymblepharis but is obviously closely related to Trichostomum (subg. Oxystegus) tenuirostre by the upper laminal areolation of evenly thickened, rectangular cells, although the well developed sclerodermis is a character more common in subg. Trichostomum. Collections of Pseudosymblepharis schimperianum of small stature have been in the past assigned to Tortella (e.g. the synonyms Tortella mollissima, Tortella richardsii and Tortella subfragilis) because of a tendency for such small plants to have less well-marked sheathing leaf bases. The names Tortella, Trichostomum, Pseudosymblepharis and Oxystegus may actually represent only one genus, characterized by a usually vee-shaped basal cell arrangement, a vee-shaped transverse section of the dorsal stereid band (in most species), an often thick-walled central cylinder, and sturdy, non-collapsing hyaloderm cells, but further research is necessary. Barbula, Didymodon, Bryoerythrophyllum, and even Pseudocrossidium have occasionally been treated even in recent times (e.g. Nyholm 1989) as a single genus under the name Barbula s. lat., and it has been a temptation to similarly unify Tortella and Trichostomum s. lat. here pending further study. As a possible parallel to be pursued in future studies of Tortella and Trichostomum, the above four groups of Merceyoideae have been successfully separated in recent studies (Saito 1975a; Zander 1978e, 1978g, 1979f, 1981a, 1981c) as genera each with considerable variation in the development of the peristome, but taxonomically distinguishable by gametophytic features. Because it is thought, however, that good gametophytic characteristics will eventually be used to place at least the type species of Tortella and Trichostomum in separate genera, these two generic names are accepted here as representing different taxa, albeit with the counsel that the present descriptions are based on species many of which will probably be redistributed at some future date among two or more generic names. It is emphasized here that Tortella cannot be adequately revised taxonomically unless Trichostomum s. lat. and Hyophila are reviewed at the same time. Species of Tortella and some related genera may usually be distinguished from many other plane-margined taxa, mainly those of the Barbuleae, by the stem section. Although presence of a central strand is variable, as a rule the hyalodermis is present, composed of rectangular (in transverse section) cells that are seldom collapsed in mature parts of the stem, and the sclerodermis is generally only weakly developed, often of substereid cells only slightly smaller than those of the central cylinder or of a few scattered stereid cells. Often, the cells of the central cylinder are thick-walled. Taxa of Merceyoideae with a hyalodermis have it composed of rounded cells, these usually collapsed except in the region of the extreme stem apex, and have a distinct sclerodermis of one or more layers of stereid cells. Pleurochaete has a similar vee of basal cells, but in that genus the thin-walled basal marginal cells form a group easily distinguished from the thicker-walled inner basal cells.
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Number of accepted species:
53
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Species Examined:
T. acaulon (NY), T. alpicola (BUF, CANM, NY), T. bryotropica (BUF), T. cirrifolia (NY), T. cryptocarpa (NY), T. cyrtobasis (BM), T. densa (DUKE, NY), T. eckendorffii (PC), T. flavovirens (BUF), T. fragilis, T. fruchartii (H, NY), T. germainii (NY), T. goniospora (NY), T. hildebrandtii (NY), T. humilis, T. inclinata (BUF), T. inflexa (BUF), T. japonica (BUF), T. knightii (MO, NY), T. lilliputana (NY, S), T. linearis (NY), T. nitida (BUF), T. novae-valesiae (H), T. pseudocaespitosa (NY), T. rigens (DUKE, NY), T. rubripes (NY), T. simplex (US), T. somaliae (NY), T. tortuosa, T. xanthocarpa (H, NY).
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Plants loosely caespitose or forming turfs or cushions, green to dark green above, brown to tan below. Stems branching occasionally or often, usually short but up to 4 cm in length, in transverse section rounded-pentagonal, central strand absent, weak or strong, cells of central cylinder often thick-walled, sclerodermis present but usually weak, hyalodermis present, occasionally weak or only in patches, composed of cells that are not or little collapsed when mature; axillary hairs long, ca. 10–20 cells in length, all hyaline; weakly radiculose, occasionally matted with reddish brown rhizoids. Leaves often crowded, when dry appressed, erect or incurved, often twisted or contorted, occasionally spiralled about stem, spreading when moist, ligulate to long-lanceolate, rarely spathulate, 1.5–7.0 mm in length, upper lamina flat, broadly channeled across leaf or weakly channeled along costa, margins plane, occasionally erect or narrowly incurved or tubulose, entire, weakly crenulate with projecting papillae or seldom weakly dentate near apex or below midleaf, rarely bordered with elongate cells near apex; apex subulate or narrowly to broadly acute, occasionally rounded or cucullate; base oblong, elliptical or short-ovate, occasionally long-sheathing or not differentiated in shape; costa ending 1–4 cells below apex, percurrent or more usually short-excurrent as a mucro, superficial cells quadrate or elongate, occasionally only quadrate at midleaf ventrally, elongate dorsally, 2–6(–10) rows of cells across costa ventrally at midleaf, costal transverse section semicircular or ovate, stereid bands two, weak to strong ventrally, strong dorsally, epidermis present ventrally and present, weak or absent dorsally, guide cells 4–6(–8) in 1 layer, hydroid strand absent; upper laminal cells quadrate to hexagonal, occasionally bistratose, 7–15 µm in width, 1(–2):1, walls thin to evenly thickened, superficially convex on both sides; papillae spiculose, bifid or occasionally simple, 3–6 per lumen, seldom capituliform and centered; basal cells differentiated across leaf in a vee-shape, usually sharply differentiated, occasionally forming only a low vee or weakly differentiated from the upper cells, rectangular, occasionally bulging, ca. 8–30 µm in width, 4–6:1, walls thin or evenly thickened to porose, usually smooth. Asexual reproduction occasional, apparently by fragile leaf apices or portions of lamina. Dioicous or occasionally autoicous. Perichaetia terminal, inner leaves usually long-lanceolate, to 6 mm in length, usually sheathing the seta, lower cells long-rhomboidal in lower 1/2. Perigonia terminal, weakly gemmate, inner leaves smaller, or occurring as flattened, stalked, buds in leaf axils of perichaetiate plants. Seta ca. 0.7–3.0 cm in length, 1 per perichaetium, yellowish, reddish or light brown, twisted clockwise below, occasionally counterclockwise above, seldom straight; theca ca. (1.0–)1.5–3.0 mm in length, yellowish to reddish brown, cylindrical or occasionally elliptical, exothecial cells rectangular, 20–45 µm in width, 3–5:1, seldom hexagonal, walls thin, stomates at base of theca, phaneropore, annulus of 1–4 rows of weakly or strongly vesiculose cells, persistent; peristome teeth 32, linear, spiculose, occasionally branching-spiculose, ca. 550–1400 µm, with many articulations, twisted counterclockwise, usually two or three times, basal membrane absent or low, papillose to spiculose, or rarely absent, or capsule rarely cleistocarpous and then elliptical and long-apiculate. Operculum long-conic to rostrate, ca. 1.0–2.5 mm in length, cells twisted counterclockwise, seldom undifferentiated. Calyptra cucullate, smooth, 2.5–3.5 mm in length. Spores 8–20 µm in diameter, yellowish brown, essentially smooth or papillose. Laminal KOH color reaction usually yellow, sometimes yellowish orange or reddish brown, leaves often yellow when immature but orange lower on the stem. Reported chromosome number 7, 13, 13+m, 14, 15, 26, 30, 52.
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