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Published In: Bryologia Universa 2: 81. 1827. (Bryol. Univ.) Name publication detailView in Biodiversity Heritage Library

Project Name Data (Last Modified On 10/25/2011)
Acceptance : Accepted
Project data     (Last Modified On 10/25/2011)

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.


     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.

Notes:            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.

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).


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            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.

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