Pseudochorisodontium in Moss Flora of China @ efloras.org

28. Pseudochorisodontium (Broth.) C. Gao, Vitt, X. Fu & T. Cao, Moss Fl. China. 1: 220. 1999; Dicranum subg. Pseudochorisodontium Broth., Nat. Pflanzenfam. (ed.2) 10: 207. 1924.

Plants medium-sized to large, 4–10 cm high, coarse to fairly robust, sometimes slender, yellowish green or brownish green, shiny, in loose or dense tufts. Stems erect, simple or sparsely branched, rarely densely branched, radiculose at base; central strand present. Leaves loosely appressed, flexuose or falcate-secund when dry, erect-spreading when moist, thin and translucent, ovate-lanceolate or lanceolate, abruptly or gradually narrowed from a broadly ovate, clasping base or from an oblong-ovate or lanceolate base to a setaceous or a long, slender acumen; margins plane below or incurved above, entire or serrulate in the upper part; costa narrow, slender, subpercurrent to shortly excurrent, smooth or weakly serrulate at back above, not ridged; upper cells quadrate or rhomboidal to oblong-ellptical, smooth or papillose; basal cells elongate, rectangular or nearly so, thick-walled, porose; alar cells well differentiated, somewhat bulging out, incrassate, 2–5(–6) stratose, reddish brown. Dioicous. Perichaetial leaves strongly sheathing at base, abruptly narrowed to a short or long, subulate acumen. Setae straight, 1–3 per perichaetium, yellowish brown or reddish brown; capsules erect, cylindric, symmetric, reddish brown, not strumose; stomata absent; opercula erect, long-rostrate, nearly as long as the urns; peristome teeth absent or highly reduced. Calyptrae cucullate, entire at base. Spores spherical, smooth or minutely papillose.

Type. Dicranum gymnostomum Mitt., J. Proc. Linn. Soc., Bot., Suppl. 1: 14. 1859.

The subgenus Pseudochorisodontium as circumscribed by Brotherus (1924) was not exclusive, because it includes taxa that are not distinguishable from other subgenera of Dicranum. During our study of Chinese Dicranum species, we found that a group of species share a peculiar feature of sporophyte structure in which the peristome teeth are absent. This feature in combination with other characters gives the group generic recognition. The genus Pseudochorisodontium, including six species, is found to be restricted to Himalayan regions and the southwestern high plateau of China. The characteristics of the genus are: 1) leaves generally with broadly ovate or oblong-ovate base, abruptly to gradually narrowed to a setaceous or subulate acumen; 2) alar cells 2–5 stratose, inflated, reddish brown; 3) capsules erect, cylindric, symmetric, not strumose, and without stomata; and 4) peristome teeth absent or highly reduced.

1 Leaves abruptly narrowed from a broadly ovate base to a setaceous acumen; leaf margins entire or nearly so (2)

+ Leaves gradually narrowed from an oblong-ovate or lanceolate base to a long, slender acumen; upper leaf margins serrulate (3)

2 (1) Leaf acumina falcate-secund or curved, longer than the base; upper cells distinctly mammillose at back 1 Pseudochorisodontium conanenum

+ Leaf acumina erect-flexuose or contorted, as long as or shorter than the base; upper cells smooth or sometimes low mammillose at back 5 Pseudochorisodontium ramosum

3 (1) Alar cells 4-5 stratose (4)

+ Alar cells 2-3 stratose (5)

4 (3) Leaf base oblong-ovate; upper leaf cells coarsely spinose 4 Pseudochorisodontium mamillosum

+ Leaf base lanceolate; upper leaf cells low papillose 6 Pseudochorisodontium setschwanicum

5 (3) Upper and median leaf cells elongate, rhomboidal or oblong-elliptical, projecting at the cell ends 2 Pseudochorisodontium gymnostomum

+ Upper and median leaf cells short, quadrate or irregularly rounded quadrate, papillose 3 Pseudochorisodontium hokinense

Lower Taxa