29. ANOECTANGIUM Plate 38.

Anoectangium Schwaegr., Spec. Musc. Suppl. 1(1): 33, 1811, nom. cons. non Anoectangium Röhl, 1809, nom. rejic. Type: Anoectangium compactum Schwaegr.

Anictangium Hedw., Spec. Musc. 40, 1801, nom. rejic.

Anyctangium Hedw. in Lam. & Cand., Fl. Franc. 2: 444, 1805, orthogr. var.

Pleurozygodon Lindb., Utkast Nat. Grupp. Eur. Lavmoss. 35, 1878. Type: Pleurozygodon aestivus (Hedw.) Lindb.

Anoectangium subg. Euanoectangium Roth, Eur. Laubm. 1: 171, 1904, nom. illeg. Type: Anoectangium compactum Schwaegr.

Anoectangium subg. Pleurozygodon (Lindb.) Kindb., Eur. N. Amer. Bryin. 2: 317, 1897.

Gymnostomum sect. Anictangium (Hedw.) Leman, Dict. Sc. Nat. 20: 151, 1821.

Zygodon sect. Anoectangium C. Müll., Syn. 1: 683, 1849.

Plants growing in turf or mats, green to yellow-brown above, light to dark brown below. Stems seldom branching, to 1(–3) cm in length, transverse section oval to rounded-triangular or pentagonal, central strand present, strong, outer cortex with smaller lumens, usually thick-walled, hyalodermis absent; axillary hairs of 3–10 cells, all hyaline or basal 1–2 brownish and with thicker walls; weakly radiculose or with red-brown tomentum. Leaves often distant or crowded, occasionally secund, appressed-incurved, often twisted when dry, spreading when moist, ligulate to lanceolate, occasionally triangular or acuminate, 1.0–1.5(–2.0) mm in length, upper lamina strongly keeled, deeply grooved along costa, margins plane or weakly recurved in lower 1/2, entire, occasionally finely crenulate or weakly denticulate above; apex broadly obtuse to sharply acute, usually apiculate, occasionally acuminate or somewhat cucullate; base scarcely differentiated in shape or ovate; costa ending at the apiculus or sometimes a fewcells below apex or becoming short-excurrent as a mucro, seldom stoutly excurrent, superficial cells elongate or occasionally short-rectangular to quadrate near apex ventrally, elongate dorsally and generally papillose, 2–3 cells across costa ventrally at midleaf, costal transverse section oval to reniform, stereid band single, strong, semicircular to oval, epidermis absent ventrally (the guide cells superficially exposed) to weakly developed, epidermis usually distinct dorsally, guide cells 2–4 in 1 layer, hydroid strand absent; upper laminal cells subquadrate, occasionally hexagonal or elongate transversely or longitudinally in patches, (5–)7–9(–15) µm in width, 1(–2):1(–2), walls thin to greatly thickened, superficially flat to bulging, occasionally in extraplanar rows (very seldom bistratose); papillae multifid, often massively so, centered over the lumens or simple to bifid, scattered, rarely absent; basal cells differentiated in a small group at base of costa, short-rectangular, little wider than upper cells, 2–4:1, walls usually thick-walled. Dioicous. Perichaetia terminal on short lateral branches, inner leaves ovate-acuminate, 1.0–1.5 mm in length, convolute-sheathing, lower cells short-rhomboidal to near apex. Perigonia lateral. Seta 0.3–0.8 cm in length, 1 per perichaetium, yellow-brown, twisted clockwise below, occasionally counterclockwise above; theca 0.5–1.0(–1.5) mm in length, yellow-brown to brown, ovoid to elliptical, exothecial cells rectangular, walls thin, stomates phaneropore, at base of theca, annulus of two rows of weakly vesiculose cells; peristome absent. Operculum long-rostrate, 0.4–0.6(–1.8) mm in length, sometimes longer than the theca, inclined, cells in straight rows. Calyptra cucullate, smooth, 1.2–1.5(–2.0) mm in length. Spores 9–12(–19) µm in diameter, light brown, weakly to strongly papillose. Laminal KOH color reaction yellow to yellow-orange. Reported chromosome number n = 13.

A rather large but singularly homogeneous group distributed mainly in tropical, arctic or mountane areas of the world.

Anoectangium is unusual in that the distinctions between the many species are mainly in characters considered variable in other genera. A close study of the Middle American representation (Zander 1977c) resulted in extensive synonymy with only one species, A. aestivum (Pl. 38, f. 10–13), recognized for the area. The most common expression of the species in the area was found to have small, superficially bulging laminal cells with multifid papillae centered over the lumens. Considered weakly distinguishable were certain uncommon, mostly local variants with various leaf shapes and usually superficially flat, larger upper laminal cells having thickened walls, often transversely or longitudinally elongate medially, the laminal papillae low, simple, seldom multifid. Some collections, however, showed independent segregation of these features.

Review of a series of exotic taxa for this study indicate that the Middle American variation is repeated on a larger and possibly more distinctly stepwise scale, with taxonomic distinctions dependent on combinations of leaf shape, and details of the areolation and papillae morphology. A Mexican morphological variant with a tendency for upper laminal cells to have massive, centered, capituliform papillae, and for the cells to protrude superficially on one side of the leaf or the other in spaced rows or patches (these often bistratose) was found to occur also in South Africa (as A. wilmsianum, Natal, Cathedral Peak Forest Station, Magill 5532, PRE). Whether this represents a vicariance event or polytopic differentiation is unknown; however, it may be pointed out that another South African taxon, Tortula ammonsiana, also occurs rarely in eastern North America, which is a disjunction of equal geographic magnitude.

Anoectangium is generally distinguishable from a similar genus with very short sporophyte-bearing branches arranged laterally on the axis, Molendoa, by its constant lack of a ventral costal stereid band (Pl. 38, f. 7, 11, 20, 28), but see the discussion of Molendoa for additional comments. Norris and Koponen (1989) suggested that “the apparent lateral perichaetia (Pl. 38, f. 1) may be interpreted as resulting from innovation below the still very immature perichaetia.” The narrow leaves appear to distinguish Anoectangium from Pottioideae taxa with single stereid bands, and the rather strongly differentiated stem sclerodermis is clearly that of the Merceyoideae. The single stereid band, however, cannot be attributed to small plant size alone (as is the case in certain single-stereid banded collections of species of Didymodon and Gymnostomum, and other genera of Merceyoideae). Syntrichia abruptinervis is similar to Anoectangium species in the lanceolate leaves with a deep, narrow groove along the costa, but differs significantly in the inflated basal cells, costa arcuate in section, hydroid strand present, and the red KOH reaction. Anoectangium shares the distinctive deep groove running up the ventral side of the leaf at the costa with Barbula species, along with similar papillae and KOH color reaction, among other characters. Molendoa, on the other hand, is similar to Didymodon in many characters, though placed in the Hyophileae of Cladograms 14–16.

Additional literature: Geissler (1985), Malta (1921), Newton (1983), Rashid (1970), Saxena and Gill (1986), Saxena and Rashid (1980), Zander and Vitt (1979).

Number of accepted species: 47.

Species examined: A. abyssinicum (BM), A. aestivum, A. afrocompactum (NY), A. angustifolium (NY), A. bicolor (NY), A. borbonense (FH), A. clarum (BUF), A. eukilimandscharicum (BM), A. hobsonii (NY), A. humblotii (FH), A. impressum (BM, FH), A. keniae (PC), A. lineare (NY), A. mafatense (FH), A. magnirete (FH), A. raphidostegium (NY), A. rufoviride (DUKE), A. shepherdae (PC), A. strachyanum (BUF, NY), A. thompsonii (DUKE, NY), A. walkeri (DUKE), A. wilmsianum (NY).

New combinations: Anoectangium keniae (P. de la Varde) Zand., comb. nov. (Gymnostomum keniae P. de la Varde, Rev. Bryol. Lichénol. 22: 10, 1953). Anoectangium shepherdae (Card. & Dix.) Zand., comb. nov. (Hymenostylium shepherdae Card. & Dix., J. Bot. 48: 307, 1910).

New synonymy: Anoectangium compactum var. alaskanum Card. & Thér. Am1 = Anoectangium aestivum (Hedw.) Mitt. Anoectangium sordidum Mitt. = Hymenostylium recurvirostrum (Hedw.) Dix.