65. MICROBRYUM Plate 93.

Microbryum Schimp., Syn. 10, 1860. Type: Microbryum floerkeanum (Web. & Mohr) Schimp.

Bryella Berk., Handb. Brit. Mosses 16: 300, 1863, Type: Bryella recta (With.) Berk.

Cycnea Berk., Handb. Brit. Moss. 60, 301, 1863, hom. illeg. non Cycnia Griff., 1854. Type: Cycnea curvicolla (Hedw.) Berk.

Pottiella (Limpr.) Gams, Krypt. Fl. Mitteleur. ed. 2, 1: 101, 1948.

Lydiaea Laz., Not. Syst. Sect. Cryptog. Inst. Bot. Nom. Komar. Acad. Sci. URSS 12: 280, 1959. Type: Lydiaea vlassovii (Laz.) Laz.

Phascum subg. Microbryum (Schimp.) Limpr., Laubm. Deutschl. 1(3): 182, 1885.

Phascum subg. Pottiella Limpr., Laubm. Deutschl. 1: 188, 1885. Type: Phascum curvicollum Hedw., lectotyp. nov.

Pottia subg. Pottiella (Limpr.) Broth., Nat. Pfl. 1(3): 423, 1902.

Phascum sect. Pottiella (Limpr.) Par., Actes Soc. Linn. Bordeaux 51[1]: 66, 1897; Ind. Bryol. [4]: 1030, 1898.

Acaulon sect. Microbryum (Schimp.) C. Müll., Gen. Musc. Fr. 20, 1900.

Phascum sect. Microbryum (Schimp.) Podp., Consp. Musc. Eur. 221, 1954.

Pottia sect. Pottiella (Limpr.) Nyholm, Ill. Fl. Nordic Mo. 2: 81, 1989.

Pottia subsect. Muticae C. Jens., Skand. Bladmfl. 210, 1939, nom. inval. descr. suec.

Plants forming a low turf, scattered or gregarious, occasionally bulbiform, reddish brown above, brown below. Stems seldom branching, extremely short, 0.2–0.4 µm in length, transverse section round to rounded-pentagonal, central strand present or absent, sclerodermis absent or weakly differentiated, hyalodermis absent; axillary hairs 3–6 cells in length, the basal 1–2 usually with thicker walls; rhizoids sparse. Leaves appressed when dry, weakly spreading and tips occasionally reflexed when moist, lanceolate, elliptical or ovate, occasionally spathulate, short, 0.6–1.8 µm in length, upper lamina weakly concave to broadly channeled, margins recurved at midleaf, commonly narrowly recurved to near apex, entire or rarely serrulate near apex, marginal cells often less papillose and somewhat thicker walled than the medial; apex broadly acute; base not differentiated; costa excurrent as an apiculus or forming a mucro or short awn, occasionally only percurrent, costa with lamina inserted laterally, superficial cells smooth or papillose, ventrally quadrate or short-rectangular or elongate, dorsally short-rectangular to elongate, 2(4–6) rows of cells across costa ventrally at midleaf, costal transverse section usually round, stereid band present dorsally, round to semicircular in shape, ventral and dorsal epidermises present, guide cells 2(–4) in 1 layer, hydroid strand present, occasionally centrally located in the stereid band, occasionally the ventral epidermis differentiated as a pad of enlarged parenchymatic cells; upper laminal cells quadrate to hexagonal or short-rectangular, occasionally rhomboidal, rather large, 11–20 µm in width, 1–2:1, walls thin to moderately and evenly thickened, superficially convex on both sides; papillae usually simple, seldom bifid, hollow, 1–6 per lumen, occasionally branching and tall; basal cells differentiated across leaf or higher medially, rectangular, ca. 18–30 µm in width, 2–4:1, walls usually thin. Monoicous, usually paroicous, occasionally synoicous. Perichaetia terminal, inner leaves often somewhat enlarged, otherwise little different from the cauline. Seta nearly absent to 4 µm in length, 1(–2) per perichaetium, yellow-brown, twisted straight or counterclockwise below and clockwise above; theca cleistocarpous or stegocarpous, ca. 0.5–1.1 µm in length, brown or reddish or yellowish brown, ovate to short-elliptical, apiculate when cleistocarpous, exothecial cells short-rectangular, ca. 18–25 µm in width, mostly 2–5:1, thin-walled, stomates phaneropore, at base of theca, annulus absent or of 1–2 rows of weakly vesiculose cells, persistent; eperistomate or peristome teeth 16, irregular, often rudimentary, often apically truncate, ligulate to triangular, spiculose, short, with few articulations, straight, basal membrane absent. Operculum when differentiated low-conic, ca. 0.1–0.2 µm in length, cells straight. Calyptra mitrate to conic-cucullate, smooth or finely papillose, ca. 0.2–0.8 µm in length. Spores ca. 20–30 µm in diameter, light brown, essentially smooth to warty or spiculose or hollow-tuberculate. Laminal KOH color reaction red. Reported chromosome numbers: n = 26, 27+m, 28, 30.

Found in the temperate zones worldwide, especially in somewhat arid situations, mainly on soil.

Microbryum is distinctive in the combination of the small habit, red KOH color reaction of the upper lamina, single round to semicircular costal stereid band (Pl. 93, f. 7, 14), capsules apiculate when cleistocarpous (Pl. 93, f. 19), peristomes when present commonly apically truncate and seemingly large in comparison with the size of the capsule; and calyptrae often papillose (Pl. 93, f. 10, 22). If one considers the possibility that taxa with single stereid bands evolved independently from taxa with two stereid bands, then Microbryum might have been derived through reduction from ancestors of Bryoerythrophyllum, which has similar areolation. Evidence for this is that there are no other highly reduced taxa related to Bryoerythrophyllum (see also discussion of Saitoella and Acaulon). Otherwise, Microbryum could have come from progenitors similar to Tortula sect. Tortula. Cladograms 11 and 14, however, indicate a different derivation.

Chamberlain's (1969, 1978) treatment of Pottia species with erostrate opercula recognized M. starckeanum as a single species including both tuberculate and papillose-spiculose spored plants. The present study, however, supports the traditional arrangement of Corley et al. (1982) that distinguishes material differing by the two spore ornamentations at the species level. Chamberlain's infraspecies are all recognized at the varietal level, with the addition of M. davallianum var. commutatum and M. starckeanum var. fosbergii. All varieties of these two species that were recognized by Chamberlain (1978) for Gt. Britain are also present in U.S.A. in California. One collection, California, Pasadena, s.n., “g. 9”, US, includes M. starckeanum var. starckeanum, var. fosbergii, and an intermediate with a capsule having a differentiated operculum and short peristome that is indehiscent even when boiled in KOH solution. The intermediate is also found in other collections (e.g. California, Ikenberry 369, CANM, comm. T. McIntosh). The type of Pottia arizonica (= M. starkeanum var. starckeanum) has spores that appear to be both papillose and tuberculate, but the “papillae” are loose in the spore sac as well as partially coating the spore. The type of Pottia fosbergii is more probematic, with spores that are slightly wrinkled (very weakly tuberculate) and also weakly papillose. In this case, the sporophytes and spores (if unreduced) may be of hybrid origin; other specimens clearly of var. fosbergii (operculum not differentiated at all) have the spores typical of M. starckeana. Microbryum davallianum var. conicum may have spores that are epapillose, but these are never wrinkled. The two species may be seen as two series of infraspecific peristome reduction.

The calyptrae are roughened with low, simple papillae in many of the species with comparatively large calyptrae (e.g. M. commutatum, M. rectum); calyptral papillae are apparently absent in those species with much reduced sporophytes and tiny calyptrae. The presence of calyptral papillae helps distinguish this genus from Acaulon (which, like highly reduced members of Microbryum, has strongly bulging vaginulae), Syntrichia and Tortula sect. Tortula. The new combination Microbryum rufochaete reflects the strongly apiculate capsules and recurved upper laminal margins of this species. Microbryum tasmanicum is similar but has simple laminal papillae. In M. rufochaete the perigoniate plants are about a quarter to a third the size of the perichaetiate plants, and are situated near the base of the perichaetiate plants (possibly rhizautoicous).

McIntosh (1989) discussed M. vlassovii for North America (as Phascum). Both M. vlassovii and M. raddei have an enlarged pad of parenchymatic cells ventrally on the costa. Carrión et al. (1990) described the spore morphology of several species of Microbryum (as Phascum), and indicated that the spore surface of M. vlassovii was rather different from that of M. curvicolle (Pl. 93, f. 16–19) and M. floerkeanum (Pl. 93, f. 23–28), being more like that of Tortula atherodes (discussed as P. cuspidatum).

Additional literature: Guerra et al. (1991, 1992).

Number of accepted species: 13.

New heterotypic synonymy: Pottia arizonica Wareham in Grout = Microbryum starckeanum (Hedw.) Zand. var. starckeanum. Pottia arizonica var. mucronulata Wareham in Grout = Microbryum starckeanum var. brachyodus (BSG) Zand.

Species examined: M. brevicaule (NY), M. curvicolle (NY), M. davallianum (BUF, CANM, FH, US), M. floerkeanum (NY), M. longipes (BUF), M. raddei (H), M. rectum (BUF), M. rufochaete (NY), M. starckeanum (BUF, CANM), M. subplanomarginatum (BUF), M. tasmanicum (BM), M. vlassovii (BUF), M. zeelandiae (NY).

New combinations and statuses:

Microbryum brevicaule (Tayl.) Zand., comb. nov. (Gymnostomum brevicaule Tayl., London J. Bot. 5: 42, 1846; Pottia brevicaulis (Tayl.) C. Muell.).

Microbryum curvicolle (Hedw.) Zand., comb. nov. (Phascum curvicolle Hedw., Spec. Musc. 21, 1801; Pottia curvicollis (Hedw.) Mitt.).

Microbryum davallianum (Sm.) Zand., comb. nov. (Gymnostomum davallianum Sm., Ann. Bot. 1: 577, 1805; Pottia davalliana (Sm.) C. Jens.).

Microbryum davallianum var. commutatum (Limpr.) Zand., comb. nov. (Pottia commutata Limpr., Laubm. Deutschl. 1: 537, 1888; Pottia davalliana subsp. commutata (Limpr.) Podp.).

Microbryum davallianum var. conicum (Schleich. ex Schwaegr.) Zand., comb. nov. (Gymnostomum conicum Schleich. ex Schwaegr., Sp. Musc. Suppl. 1(1) 25, 1811; Pottia starckeana ssp. conica (Schleich. ex Schwaegr.) Chamberl.).

Microbryum floerkeanum var. arbense (Loitl.) Zand., comb. nov. (Phascum arbense Loitl., Verh. Zool. Bot. Ges. Wien 59: 55, 1909; Phascum floerkeanum var. arbense (Loitl.) Podp.), not seen.

Microbryum longipes (Guerra, Martínez & Ros) Zand., comb. nov. (Phascum longipes Guerra, Martínez & Ros, J. Bryol. 16: 55, 1990 as “longipedis” typographical error cf. J. Bryol. 16: 335, 1991).

Microbryum raddei (Broth.) Zand., comb. nov. (Tortula raddei Broth., Bot. Centralbl. 34: 26, 1888).

Microbryum rectum (With.) Zand., comb. nov. (Phascum rectum With., Syst. Arr. Britt. Pl. ed. 4: 771, 1801; Pottia recta (With.) Mitt.).

Microbryum rufochaete (Magill) Zand., comb. nov. (Acaulon rufochaete Magill, Fl. S. Afr. I. Bryophyta 1: 201, 1981 [1982]).

Microbryum starckeanum (Hedw.) Zand., comb. nov. (Weisia starckeana Hedw., Spec. Musc. 65, 1801; Pottia starckeana (Hedw.) C. Müll.).

Microbryum starckeanum var. brachyodus (BSG) Zand., comb. nov. (Anacalypta starckeana var. brachyodus BSG, Bryol. Eur. 2: 47, 1843; Pottia starckeana var. brachyodus (BSG) C. Müll.), commonly “brachyoda.”

Microbryum starckeanum var. brevidens (Latz.) Zand., comb. nov. (Pottia starckeana var. brevidens Latz., Beih. Bot. Centralbl. 48(2): 483, 1931), not seen.

Microbryum starckeanum var. fosbergii (Bartr.) Zand., comb. nov. (Pottia fosbergii Bartr., Bryologist 33: 18, 1930; Pottia starckeanum var. fosbergii (Bartr.) Zand.).

Microbryum starckeanum var. leiostoma (Corb. in Corb. & Pitard) Zand., comb. nov. (Pottia starckeana var. leiostoma Corb. in Corb. & Pitard, Bull. Soc. Bot. France 56: ccxxiv, 1909), not seen.

Microbryum starckeanum var. subgymnostoma (De Not.) Zand., comb. nov. (Anacalypta starckeana var. subgymnostoma De Not., Atti Univ. Genova 1: 583, 1869; Pottia starckeana var. subgymnostoma (De Not.) Grav.), not seen.

Microbryum starckeanum var. submutica (Latz.) Zand., comb. nov. (Pottia starckeana var. submutica Latz., Beih. Bot. Centralbl. 48(2): 483, 1931), not seen.

Microbryum starckeanum fo. brevifolium (Limpr.) Zand., comb. nov. (Pottia starckeana fo. brevifolia Limpr., Laubm. Deutsch. 1: 536, 1888), not seen.

Microbryum starckeanum fo. dextrorsum (Limpr.) Zand., comb. nov. (Pottia starckeana fo. dextrorsa Limpr., Laubm. Deutsch. 1: 536, 1888), not seen.

Microbryum starckeanum fo. microphyllum (Warnst.) Zand., comb. nov. (Pottia starckeana fo. microphylla Warnst., Hedwigia 58: 144, 1917), not seen.

Microbryum subplanomarginatum (Dix.) Zand., comb. nov. (Pottia subplanomarginata Dix., Trans. R. Soc. S. Afr. 18: 253, 1929).

Microbryum tasmanicum (Dix. & Rodw.) Zand., comb. nov. (Phascum tasmanicum Dix. & Rodw., Pap. Proc. R. Soc. Tasmania 1923: 25, 1923).

Microbryum vlassovii (Laz.) Zand., comb. nov. (Phascum vlassovii Laz., J. Inst. Bot. Ac. Sc. R.S.S. Ukraine 26–27: 196, 1938).

Microbryum zeelandiae (R. Br. ter) Zand., comb. nov. (Anacalypta zealandiae R. Br. ter, Trans. Proc. New Zealand Inst. 30: 413, 1898; Pottia zealandiae (R. Br. ter) Par.).