24. HYMENOSTYLIUM Plates
31
- 32.
Hymenostylium Brid., Bryol. Univ. 2: 81, 1827. Type: Hymenostylium xanthocarpum
(Hook.) Brid.
Gymnoweissia Mont. in Orbigny, Dict. Univ. Hist. Nat. 7: 402, 1849.
Hymenostelium Engl., Syllab. 48, 1892, nom. inval. err. pro Hymenostylium
Brid.
Barbula subg. Hymenostylium (Brid.) Lindb., Musci Scand. 22, 1879.
Weissia subg. Hymenostylium (Brid.) Kindb., Eur. N. Amer. Bryin. 2:
283, 1897.
Gymnostomum sect. Hymenostylium (Brid.) Griff., Calcutta J. Nat. Hist. 2:
480, 1842.
Gymnostomum sect. Vera Griff., Calcutta J. Nat. Hist. 2: 478, 1842, p.p.,
nom. illeg.
Pottia sect. Hymenostylium (Brid.) C. Müll., Syn. 1: 562, 1849.
Weissia sect. Hymenostylium (Brid.) Mitt., J. Linn. Soc. Bot. 12: 134,
1869.
Barbula sect. Hymenostylium (Brid.) Braithw., Brit. Moss Fl. 1: 258,
1887.
Plants growing in turfs or cushions, often flagellate,
green, often glossy, occasionally glaucous above, light brown below.
Stems often branching, to 3(–8) cm in length, occasionally papillose, transverse
section rounded-pentagonal to triangular, central strand usually absent,
sclerodermis present, hyalodermis usually absent; axillary hairs ca. 8
cells, basal 1–2 cells brownish or occasionally all hyaline; often with a
red tomentum. Leaves often distant on stem, appressed-incurved,
sometimes twisted or lax when dry, spreading, occasionally squarrose when
moist, ligulate to lanceolate or linear-lanceolate, ca. 2.0(–3.5) mm in
length, upper lamina keeled, margins plane to broadly recurved
(occasionally revolute) along 1 or both sides, entire or rarely
serrulate near apex by projecting cell walls, rarely bistratose in patches
along margins or medially; apex acute, occasionally obtuse or rounded;
base scarcely differentiated in shape to oval or rectangular,
occasionally narrowly decurrent; costa often stout, sometimes ending 1–2
cells below apex or percurrent or more usually excurrent as a broad mucro,
often “scalloped” along margins by projecting cell walls, superficial cells
usually elongate ventrally, short- to long-rectangular dorsally, 2–4 or
occasionally several rows of cells across costa ventrally at midleaf, costal
transverse section semicircular to round, two stereid bands usually present,
the dorsal crescent-shaped, epidermis usually absent ventrally, often
absent dorsally, guide cells 2–4 in 1 layer, hydroid strand absent; upper
laminal cells usually heterogeneous in size and shape, quadrate to
rectangular or rhomboidal, ca. 8–10 µm in width, 1–3:1, walls
thin-walled to trigonous, often porose, superficially flat to
somewhat convex, seldom bistratose inpatches; papillae low, simple to
granular, not obscuring lumens, centered to scattered, rarely
absent; basal cells differentiated across leaf, rectangular, little wider than
upper cells, 2–4:1, walls thin to porose. Dioicous. Perichaetia terminal, inner
leaves weakly differentiated, lanceolate, somewhat longer than the cauline,
sometimes sheathing and lower cells inflated-rectangular in lower third.
Perigonia terminal, gemmate. Seta to 1 cm in length, 1 per perichaetium,
reddish or yellowish brown, twisted clockwise; capsule occasionally systylious,
theca ca. 1 mm in length, yellowish or reddish brown, ovoid to
short-rectangular, exothecial cells thin- to thick-walled, 1–4:1, stomates
phaneropore, at base of capsule, annulus weakly vesiculose; peristome absent.
Operculum narrowly rostrate, occasionally long-conic from a flaring base,
oblique, ca. 0.5–1.0 mm in length, cells straight. Calyptra cucullate, smooth,
ca. 1.0–1.5 mm in length. Spores ca. 13 µm in diameter, brownish, weakly
papillose. Laminal KOH color reaction yellow. Reported chromosome number n =
12+m, 13.
Widespread
in the world (North, Central and South America, Europe, Asia, Africa and
Australasia), found generally on calcareous rock, rarely trees, in seepage,
along streams and rivers, near waterfalls, at various elevations.
Hymenostylium is characterized by the usual lack of a stem
central strand (Pl. 31, f. 2, 12; 32, f. 1, 10); mostly keeled,
ligulate-lanceolate leaves with a tendency to trigonous cell walls and
longitudinally elongate median leaf cells; costa with two stereid bands and the
ventral epidermis usually lacking (Pl. 31, f. 7, 16; 32, f. 5, 13); upper
laminal papillae mostly low, simple, not obscuring the lumens (Pl. 31, f. 8);
capsules ovoid to short-rectangular, sometimes systylious; and peristome
lacking. As with many hygrophiles, there is much morphological variation. In
fact, in addition to presumed ecotypic differentiation, collections of this
genus may be commonly found with leaves of rather different shape and
areolation on the same stem. The amount of variation recognized for one
species, Hymenostylium recurvirostrum (Pl. 32, all figures), in the New
World (Zander 1977c; Zander & Eckel 1982) is inclusive of that seen in
almost all species of the genus examined in the course of this study,
indicating that the genus, on revision, should be found to include far fewer
species than are presently accepted. The systylious capsule is not a constant
feature in H. recurvirostrum Hymenostylium
has many of the gametophyte characters of Leptodontium, including the
usual absence of a stem central strand (always absent in Leptodontium);
lanceolate, carinate leaves that are strongly recurved when moist; lower leaf
margins often recurved; and ventral costal cells elongate (because the ventral
epidermis is absent and the ventral stereid band is thus exposed). Hymenostylium
is particularly similar to L. viticulosoides in the usual absence
of a stem hyalodermis, often trigonous or porose laminal cell walls, upper
medial laminal cells often longitudinally elongate, and laminal papillae
simple. Some collections of H. recurvirostrum var. cylindricum
from the West Indies with denticulate upper leaf margins bear a striking
resemblance to L. viticulosoides. Leptodontium differs from Hymenostylium,
however, in the dry to mesic habitat; broad, reniform costal section;
convolute-sheathing perichaetial leaves; and long-cylindrical, peristomate
capsule with well-developed annulus. Certain Trichostomum species (T.
tortelloides and T. contractum) are also similar to Hymenostylium
in the short, eperistomate capsules with long-conic opercula (these often
falling off with the columella) and plane-margined leaves, but differ in the
presence of a stem central strand and a ventral costal epidermis, broad
acumination, and upper laminal cell walls thin and evenly bifid-papillose.
There is, also, a similarity with Didymodon sect. Fallaces,
which, in addition to having a similarly broad geographic range, also has simple
laminal papillae and an exposed ventral stereid band; D. waymouthii and D.
brotheri, which also grow in hygric habitats, have elongated, somewhat
porose medial laminal cells, and lack a central strand, and are apparently the
closest morphologically to Hymenostylium in Didymodon. Cladistic
study shows a more distant relationship between Hymenostylium and Didymodon
than between the former and Leptodontium.
Additional
study is needed of West Indian populations of H. recurvirostrum of great
morphological variability (Zander 1977c) with respect to similar variation
often recognized at the specific level in Asia.
Additional
literature: Andrews (1926, 1943), Azziz and Vohra (1988), Dixon (1927), Györffy
(1905a), Khanna (1976).
Number
of accepted species: 18.
Species
examined: H. congoanum (BM), H. contextum (L), H.
crassinervium (NY), H. dicranelloides (BM, NY), H. filiforme
(BM), H. hildebrandtii (NY), H. papillinerve (BM), H.
recurvirostrum, H. rigescens (H).
New
heterotypic synonymy: Barbula svihlae Bartr. = Hymenostylium
recurvirostrum (Hedw.) Dix. var. recurvirostrum. Gyroweisia
tophicola (C. Müll.) Kindb. = Hymenostylium recurvirostrum (Hedw.)
Dix. Hymenostylium firmum (C. Müll.) Broth. in Bartr. = Hymenostylium
recurvirostrum (Hedw.) Dix. var. recurvirostrum. Hymenostylium
luzonense Broth. (H. recurvirostrum var. luzonense
(Broth.) Bartr.) = Hymenostylium recurvirostrum var. cylindricum
(Bartr.) Zand. in Zand. & Eckel (based on Hymenostylium glaucum var.
cylindricum Bartr., 1936). Weissia venezuelensis C. Müll. (Gymnostomum
venezuelense (C. Müll.) Kindb.) = Hymenostylium recurvirostrum
(Hedw.) Dix. Molendoa burmensis Bartr. (FH) = Hymenostylium
recurvirostrum var. cylindricum (Bartr.) Zand. in Zand. & Eckel.
Molendoa sordida (Mitt.) Steere (NY) = Hymenostylium recurvirostrum
(Hedw.) Dix.
Ne w combination: Hymenostylium hildebrandtii (C. Müll.) Zand., comb. nov. (Weissia hildebrandtii C. Müll., Linnaea 40: 298, 1876; Gyroweisia hildebrandtii (C. Müll.) Kindb.).