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.
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 n = 7, 13, 13+m, 14, 15, 26, 30, 52.
Found
on soil, rock or organic substrates on all continents.
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.
Selected
bibliography: Crundwell and Nyholm (1962, 1963), Dixon (1900), Gorton and Eakin
(1958), E. J. Hill (1913), Nicholson (1910), Zander and Hoe (1979).
Number
of accepted species: 53.
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).
New
heterotypic synonymy: Astomum latifolium Broth. in Roth = Tortella
fruchartii (C. Müll.) Zand. Tortella tortelloides (Greene) Robins.
in Llano. = Tortella alpicola Dix. Trichostomum sitkanum Card.
& Thér. = Tortella tortuosa var. arctica (Arnell) Broth. in
Fedch.
New
combinations: Tortella cryptocarpa (Broth.) Zand., comb. nov. (Astomum
cryptocarpum Broth., Bih. K. Svensk. Vet. Ak. Handl. 26 Afd. 3(7): 19, 1900).
Tortella
eckendorffii (P. Varde) Zand., comb.
nov. (Hymenostomum eckendorffii P. Varde, Rev. Bryol. Lichénol. 11:
170, 1939).
Tortella
fruchartii (C. Müll.) Zand., comb.
nov. (Phascum fruchartii C. Müll., Flora 71: 4, 1888; Astomum
fruchartii (C. Müll.) Broth.).
Tortella
goniospora (C. Müll.) Zand., comb.
nov. (Barbula goniospora C. Müll., Hedwigia 37: 131, 1898).
Tortella
lilliputana (C. Müll. ex Roth)
Zand., comb. nov. (Phascum lilliputanum C. Müll. ex Roth.,
Aussereur. Laubm. 212, 1911 “liliputanum”; Tetrapterum lilliputanum
(C. Müll. ex Roth) Broth.).
Tortella
linearis (Web. & Mohr.)
Zand., comb. nov. (Barbula linearis Web. & Mohr, Ind. Mus.
Pl. Crypt. 2, 1803; Tuerckheimia linearis (Web. & Mohr) Britt.; Oxystegus
linearis (Web. & Mohr.) Hilp.).
Tortella
somaliae (C. Müll.) Zand., comb.
nov. (Hyophila somaliae C. Müll., Linnaea 40: 293, 1876).
Tortella
walkeri (Broth.) Zand., comb.
nov. (Hyophila walkeri Broth., Rec. Bot. Surv. India 1: 317, 1899).
